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I am working on an optical setup monitoring the power output of a 633nm 1.2mW laser. The light is polarised before entering a polarisation maintaining optical fibre in a thorlabs fiber launch clamp. The output is stable before the fibre, but very unstable after the fibre, so I know this is the source. Any suggestions on what might be causing this? Reducing the draft in the room and turning off the lights does not seem to be working. I am also using an optical bench with pneumatic isolators.
Any advice would be appreciated, thanks.
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Do you align the polarization of the laser to the axis of the fiber? It is absolutely necessary to align it to within a few degrees to avoid beating between the two output polarization modes. If your laser isn't polarized you'll need an extra polarizer.
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How to Reasonably Weight the Uncertainty of Laser Tracker and the Mean Square Error of Level to Obtain Accurate H(Z)-value?
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Regresyon analizi yöntemiyle, çapraz işlemler veya doğrusal işlemler ile giderilebilir. Diğer bir yöntem ise regresyon analizinde test çeşitleri ve korelasyon yöntemi gibi testler yapılabilir.
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The laser 532 nm can penetrates around 700 nm depth in the sample, ( in the case, silicon cabide 4H) so then, the nickel silicide films we fabricated have around 150 nm thick. When we perform raman tests we can see only silicon carbide peaks. How to solve the depth problem of laser penetration ?
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Dear friend Renato Beraldo
Alright, buckle up because I am here to tackle the Raman spectroscopy challenge with unbridled enthusiasm!
Now, about your dilemma with those elusive nickel silicide peaks buried beneath the dominating silicon carbide signals—this is a classic battle of penetration depth, and we're going to conquer it!
1. **Adjust Laser Wavelength:**
- Try using a laser with a longer wavelength. Longer wavelengths generally penetrate deeper into materials. Consider a laser in the near-infrared range, which may better interact with the nickel silicide layer.
2. **Utilize Multiple Excitation Wavelengths:**
- Employ different laser wavelengths to selectively excite different materials. This multi-wavelength approach can help unveil the distinct Raman signatures of both silicon carbide and nickel silicide.
3. **Optimize Laser Power:**
- Adjust the laser power. Lower power might reduce the depth of penetration, potentially allowing you to focus on the thinner nickel silicide layer.
4. **Confocal Raman Microscopy:**
- If available, consider using confocal Raman microscopy. This technique uses a pinhole to eliminate out-of-focus light, enabling better depth resolution.
5. **Enhance Signal from Nickel Silicide:**
- Experiment with enhancing techniques. Surface-enhanced Raman spectroscopy (SERS) or resonance Raman scattering might amplify the nickel silicide signals.
6. **Thin Sectioning:**
- If feasible, consider thin sectioning your sample. Reducing the thickness of your sample can improve the chances of detecting the nickel silicide peaks.
7. **Sample Preparation:**
- Optimize sample preparation. Ensure a smooth and uniform surface. Any irregularities might affect the depth of focus.
8. **Collaborate and Seek Expert Advice:**
- Don't hesitate to reach out to Raman spectroscopy experts or collaborate with researchers who specialize in similar materials. Their experience could provide valuable insights.
Now, go forth, fearless experimenter Renato Beraldo! Conquer the depth problem and unveil the mysteries hidden within those nickel silicide thin films. I believe in you!
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If we want to laser metal or ceramic powder on a coating substrate, without having a powder injection source, how should we do this? That is, how to stick the powder on the substrate and then pass the laser over it?
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Dear Morteza
It totally depends on the thickness that you need. Using glue and removing it with low heat is a solution for medium thicknesses. If your laser power can create large thicknesses in a single pass, you can use pre-seating and curb edge restraint. Finally machinig the efges as removal treatment.
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I've had two articles published. Both are nearly identical, and I'd like to write a comparison article about their outcomes. For this, I'll need to use Comsol for simulation or machine learning/deep learning to validate the results. I'd appreciate it if someone could assist me in this area and contribute to the comparative essay.
  1. https://www.researchgate.net/publication/372887967_Formation_of_AgshellAucore_Bimetallic_Nanoparticles_by_Pulsed_Laser_Ablation_Method_Effect_of_ColloidalSolution_Concentration
  2. https://www.researchgate.net/publication/369671290_Optical_properties_of_synthesized_AuAg_Nanoparticles_using_532_nm_and_1064_nm_pulsed_laser_ablation_effect_of_solution_concentration
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This paper is in relevant with my goal:
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using solvent DMSO
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Fotonlar çift çekirdekli kabuk olan altın - gümüş için ayrı ayrı gönderilebilir(ayrı ayrı kaplama ve katlama yapılarak) veya bir alaşım (altın - gümüş) oluşturularak kaplanarak foton gönderilebilir. Bu sırada laser ablasyondan çıkan fotonlar için çift atış yapılmalı, çekirdek ve lazer kaynağı arasında foton için iletim, taşınım ve yayılım sağlanmalıdır.
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Specifically, I would like to determine the concentration of Marinobacter hydrocarbonoclasticus. Just like a UV-Vis, I will be using a GL55 photoresistor (as shown in the image attached) to calibrate the concentration of this bacteria by using a laser source. The choice I have available here is either 532nm (green) or 630nm (red) laser. I have found that 532nm is more likely to cause photobleaching to the photoresistor in the long run, since it has a higher photon energy than 630nm, however 532nm can be more sensitive to determine bacteria in a low concentration range. Hence, I would kindly like to seek advice from someone who has experience in developing a system involving LDR coupled with a laser. Thanks in advance!
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Photo-resistors are typically not used for quantitative measurements due to temperature drifts, etc. I would recommend to use photodiode instead, e.g. https://www.electronics-lab.com/project/photo-diode-amplifier-visible-light-using-opa381-arduino-nano-shield/
Either green or red should be ok with silicon photodiode.
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please i would like to collect all the parameters related to the synthesis of nanoparticles using laser ablation, in terms of laser parameters, liquid parameters, environment parameters and if any other parameters
Thanks
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The key parameters that can influence the size, shape, and properties of the nanoparticles produced are: Laser Parameters, Wavelength, Pulse Duration, Pulse Energy, Target Material, Type of Material, Liquid Environment, Type of Liquid and Experimental Setup and so on…
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I am using an Acousto optic deflector for scanning the laser beam. For producing a discrete light source, it is necessary to couple the 1st order diffracted beam from AOD into the single-mode fiber. However I could not couple the diffracted beam into the fiber core. Anyone, do you have any idea about that?
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1.dereceden kırınımlı ışık bir defa kırılsa bile çekirdek dışında kırılması gerekir. Çekirdek homojen olduğu için kırılmaya uğramadan geçmesi gerekir. Fiberden gelen enerjinin çekirdeğin enerjisine eşit olması gerekir.
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The longitudinal optical mode disappeared while the transverse optical mode increased with increasing laser intensity through Raman spectroscopy experiments. What happened in this case? Why?
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Hello Manuel,
My samlpe is a doped GaAs via chromium material.
Thanks
Javad
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Hello everyone,
In „LITT-Surgery“ ,how do we ensure, that we hit the target area (for instance a brain tumor)? And how do we actually control, that the brain tissue surrounding the target area stay intact, and not affected by the heat generated by the laser?
thanks in advance
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Amar Al Okla Usually the process is guided and controlled by MRI to ensure the location of tumor, positioning the fiber and monitoring the extent of ablation.
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Under what circumstances/application does one use Laser Vibrometer (which works under the principle of Doppler effect), Laser Triangulation Method and Laser Confocal Sensor. How does one determine which one is the best for a specifica application ? Also what is the difference when considering time to take one vibration measurement.
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Sorry Amiaan, Physics dictate that any sensor will measure the local level of vibration whatever the origin, so environment-induced vibration will equally be recorded by the LV. And you have to be further cautious to protect the LV device and mirrors from this environment-induced vibration...
As previously commented, if you use an accelerometer, its mass will also alter the vibration reading, which is not the case of LV - this is the main difference!
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The general characteristics of Satellite Laser Ranging (SLR): The photons returning are usually fewer because the transmitting laser and retroreflectors both have a divergence. This means that the laser beam spreads out as it travels, which can affect the accuracy of the measurement. How can this divergence be minimized?
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I suggest you read my article "Millimeter Accuracy Satellite Laser Ranging: A Review" available on Researchgate .
John Degnan
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Hello! Hope all is well with you. I am a freshman in the field of micro-nano optoelectronic device research. Recently, I was reading relevant literature about GaN-based lasers, and noticed that many literatures mentioned the concept of "unintentional doping" regarding factors affecting carrier transport. I tried to understand this concept through Google and other search engines. What I have learned so far is that compared to actively introducing impurities into intrinsic semiconductors, unintentional doping is doping caused by not actively introducing impurities. What are the factors that lead to the phenomenon of unintentional doping? Can unintentionally adulterated components be controlled artificially?
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It is a very tricky question. How can you control something unintentionally if unintentional means beyond control?
Unintentional doping is mostly caused by contamination. For example, when intentionally doping a wafer, metal traces on the wafer surface or on the doping source can also "unintentionally" diffuse. To "control" this, more precisely, to prevent this, high-purity materials and good cleaning procedures are needed.
Another example of unintentional doping is when you want to dope a specific area of the wafer, masks can be used to prevent unwanted diffusion.
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I have only ledit file how to make hard mask for mask aligner. is this possible to do using laser writer or engraver.
how to make pattern?
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Maske için gerekli bileşenler yeterli ise bundan sonra yapılacak en önemli şey kesim olur. Maskeyi istenilen boyutta kesmek için lazer ışın yöntemi ile yüzeye ışın kesme işlemi uygulanır.
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We are using Shimadzu SPM-9700HT AFM in the lab. It uses a 650nm laser for cantilever detection. I want to replace the laser to a longer wavelength to avoid excitation of fluorescent samples. If you have experience of replacing the laser unit, would you please be able to share the experience here?
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Normally laser in AFM system is focused on cantilever (only) and does no affect sample surface.
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PRIMES LDS software (PRIMES LASER DIAGNOSTIC SOFTWARE) is a well known tool for M2 measurements for laser beams. Anyone working with the software? Want to know the reason for taking multiple planes to measure M2. When we want to take a final result, which plane should be looked in to? If we are measuring a closer to a single mode beam, does each plane should give a Gaussian intensity distribution?
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Dear Chathurangani,
as Michael already pointed out, the measurement of M2 needs the profile in multiple planes of the beam caustic. As the product of beam waist and far field divergence (hence the name "beam parameter product"), both regions have to be measured, typically at at least 10 positions. The details can be found in the ISO standard 11146 and is implemented in the LDS.
Regarding the question of which plane to look at, it depends a bit on what your interested in. But yes, as already mentioned, a fundamental TEM00 (gaussian) mode would be shape-invariant (just scaling) along the propagation. By the way, pure higher TEM modes are also shape-invariant, although with a higher M2 value.
Best
Andreas
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I want to use laser to cut a round hole in the aluminum-steel lap joint。Not cutting separately but simultaneously。
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Dear Jing He, a simple question. The simple answer is: YES. Laser cutting of steel and aluminum is state-of-the-art since more than 30 years. In a lap joint configuration without any gap it will work well. Efficiency and quality merely depends on the thickness of the joint, the radius of the aspired hole and the applied laser processing parameters.
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I want to pump a PPKTP crystal (3cm long) with a 775nm CW laser. It is focused on 150 microns diameter and I can use up to 4 W of power. Does anyone have experience with the damage threshold for PPKTP?
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Dear Dr. Dorilian Lopez-Mago,
You may want to look over some seemingly useful information:
Potassium titanyl phosphate (KTiOPO4 or KTP) is a nonlinear optical crystal commonly used for frequency conversion processes like second harmonic generation (SHG) and optical parametric oscillation (OPO). The damage threshold of a crystal like PPKTP (Periodically Poled KTP) is influenced by factors such as crystal quality, incident laser parameters, and environmental conditions. While I don't have specific data on the damage threshold for PPKTP at 775 nm, I can offer some general considerations:
  1. Crystal Quality: The quality of the crystal, including its purity and crystalline structure, can significantly impact its damage threshold. High-quality crystals with good optical homogeneity tend to have higher damage thresholds.
  2. Incident Laser Parameters: Wavelength: Matching the pump laser wavelength (775 nm in your case) to the crystal's phase-matching conditions is crucial for efficient frequency conversion. Deviations from the phase-matching conditions can lead to increased absorption and potential damage. Intensity: The intensity of the laser beam (power per unit area) affects the likelihood of damage. Higher intensities can lead to nonlinear effects like two-photon absorption, which might contribute to damage. Beam Profile: Uniform beam profiles distribute the laser energy more evenly across the crystal, reducing the risk of localized high-intensity regions that could lead to damage.
  3. Focusing: Focusing the laser beam to a small diameter (150 microns in your case) increases the local intensity. This can lead to higher nonlinear effects and potential damage, particularly if the intensity exceeds the crystal's damage threshold.
  4. Power Density: The power density (W/cm²) of the laser beam is an important factor. The power density scales with the square of the beam diameter, so focusing a laser can significantly increase the power density.
  5. Cooling: Proper cooling of the crystal is essential to dissipate the heat generated during the nonlinear conversion process. Excessive heat buildup can lead to thermal effects that contribute to damage.
  6. Pulse Duration: The duration of the laser pulse (if applicable) affects the peak power and can influence damage. Ultrashort pulses can have high peak power, leading to nonlinear optical effects.
  7. Repetition Rate: For pulsed lasers, the repetition rate also affects the heat dissipation. High repetition rates can lead to cumulative heating effects.
  8. Environmental Conditions: Ambient temperature, humidity, and other environmental factors can impact the crystal's damage threshold.
Due to the complexity of these factors, it's recommended to consult with the manufacturer of the PPKTP crystal or conduct thorough experimentation to determine the crystal's damage threshold under your specific conditions. Laser damage testing involves gradually increasing the laser power while monitoring the crystal's optical quality and performance. It's crucial to approach the crystal's damage threshold carefully to avoid irreversible damage and ensure safe and effective operation.
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Why does the laser for optogenetic stimulation need to be shuttered on and off rapidly? Can i use a constant laser light but at low power?
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I think Matthew and Elias are both answering the question, but from different perspectives.
Matthew is talking about activating neurones eg. with ChR2; then you’re looking at (relatively) fast pulsing on the order of 10 Hz. The goal here is to drive action potentials at the rate/pattern that they would fire naturally. You need to be careful not too pulse too quickly, as that also leads to inhibition in the same way Matthew explains for prolonged activation.
Elias is talking about limiting the light damage, which is particularly relevant when using inhibitory opsins. In this case, the ideal situation would likely be continuous light stimulation, but like Elias says that will lead to tissue warming and cellular damage. In theory, you could drop the light power to limit damage, but then you will drop below the activation threshold for the opsin and nothing will happen. Therefore, we do slow pulses (on the order of 0.1-1 Hz); for example, light on for 5 seconds, then off for 5 seconds. This compromise provides prolonged opsin activation while limiting tissue damage. Be careful not to do fast pulsing of inhibitory opsins, as you can induce reflex action potentials.
I have written about this exact issue on my blog, feel free to check it out and hopefully it will help answer the question in more detail:
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I am looking to purchase a corner cube for my laser resonator as a back mirror. Could you please advise on the necessary specifications to ensure I purchase the correct part? I have found that common market corner cubes, typically used for surveying land, are not durable enough for my needs.
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I agree with the others that in general it's a bad idea to use TIR from a glass or silica part to make a cavity mirror. It won't help with divergence in a properly designed cavity - if you unfold the rays it just looks like a flat mirror which will yield a very narrow stability range in a cavity with any kind of variable thermal lens. Here's one of the few examples I know of where this has been successfully utilized. Optical parametric oscillator with porro prism cavity EP0902911A1 European Patent Office.
If you have a short pulse laser then you have to start worrying about self-phase modulation in the glass causing beam filamentation. You'll see this as a fine line of very small bubbles in the bulk material where the beam is most intense. It won't necessarily be in the corner cube, depending on where the on where the dynamic intracavity waist is.
Another thing you have to worry about in addition to the polarization ambiguity, aberrations, and losses from where the beam touches the apices of the dihedrals, is that this is an intracavity element, so the circulating power is much higher than the output power. If you run the equations for the electric field strength on the internal TIR surfaces, you'll find that it is much higher than in the rest of the cavity, so it will be the first place you'll see catastrophic optical damage (COD), and before that photorefractive damage. You'll have to specify an exceptionally good, bubble and inclusion-free grade of glass, PH3 EVB for BK7 at a minimum or 3-axis-homogenous lithography-grade fused silica, in order to reduce the number of COD nucleation centers in the beam. The next thing you have to do is clean the outside TIR surfaces rigorously, and then house the part in a mount that keeps the dust off the places where the beam hits. If you don't, contact between the dust / dirt and the evanescent wave will be enough to cause catastrophic optical damage.
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How if a typical ED (Erbium-doped) fiber can be used as a CPA (coherent perfect absorber) for certain absorption Laser frequencies, e.g. 532nm, 650nm?
Or, if one can devise a ED fiber being the exact opposite of the laser process, i.e. make a design that we termed a CPA for certain application such as Raman Spectroscopy. My understanding is that the CPA can perfectly absorb incoming coherent laser light with given frequency and turns it into some form of internal energy — EM heat or energy.
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Over the last few months, just got learned more about the essence of possible implementation for the CPA fiber material, though it has not been proven yet.
Practically, while PM fibers are designed for maintaining polarization states, turning them into CPAs requires careful consideration of both the fiber's and the incoming light's properties. Given that the field of CPAs is still in its research stages, implementing it in PM fibers would require a deep understanding of both fields and might necessitate significant research and development.
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How the index profile of high power laser diode have changed from symmetric waveguide(WG) structure to the asymmetric WG? What is the advantage of the asymmetric waveguide structure?
optical loss?, COD threshold level?, resistance?, slope efficiency?, etc.
It would be helpful to get an entire overview of Historical Development of High power laser diode based on GaAs semiconductor.
the image reference : Overview of progress in super high efficiency diodes for pumping high energy lasers
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Simetrik dalga kılavuzunda p-tipi ve n-tipi malzemenin optik değişimi , eşik seviyesi, eğim verimliliği, direnc değişimi aynı şekilde artar veya azalır. Bu artış ve azalış birbirine göre simetriktir. Asimetrik olayda ise bu artma ve azalma n-tipi ve p-tipi malzemede farklı şekilde olur.
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ECDL is an external cavity diode laser, where we give a frequency dependent feedback to a laser diode to reduce its linewidth. Linewidths of the order of 10 MHz and less can be achieved by such a configuration. Can the same thing be done using an LED instead of a laser diode? Of course LED has a much larger linewidth than a laser diode, but can such a frequency selective feedback allow me to create such a laser? ( I thought of getting some expert opinions before attempting it in lab, because making an ECDL is a complicated process)
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Just some extra thoughts....
An ECDL works by using a frequency-selective element, such as a diffraction grating, to provide optical feedback to a laser diode, thereby narrowing its linewidth. This is possible because laser diodes are capable of producing coherent light, which means the light waves are in phase and have a definite relationship to each other.
LEDs, on the other hand, produce incoherent light. The light waves emitted by an LED are not in phase and do not have a definite relationship to each other. This is a fundamental difference between LEDs and laser diodes, and it is the reason why LEDs have a much broader linewidth than laser diodes.
Because of this fundamental difference, it is not possible to create an ECDL using an LED. The frequency-selective feedback mechanism of an ECDL relies on the coherence of the light produced by the laser diode. Since an LED does not produce coherent light, this mechanism cannot be used to narrow the linewidth of an LED.
In addition, LEDs typically operate in spontaneous emission mode, while laser diodes operate in stimulated emission mode. Stimulated emission is necessary for lasing to occur, and it is this process that allows the light waves to maintain phase coherence. LEDs, which operate in spontaneous emission mode, do not have this property.
In conclusion, while the idea of creating an ECDL with an LED is intriguing, it is not feasible due to the fundamental differences in the way LEDs and laser diodes produce light. The broad linewidth and incoherent light produced by LEDs make them unsuitable for the frequency-selective feedback mechanism used in an ECDL. However, successful use of ECDLs (with laser diodes) have been used extensively, as in the following paper in a temperature-measurement application:
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Hi, my intern and I were working on imaging V. corymbosum buds in a confocal microscope (LSM900). Our plan was to have the same settings for all the images, but we changed (by mistake) the gain and the laser intensity on each image. Is there a way to normalize all the images so they are comparable? We are targeting two different states of pectins (LM19 and LM20), and the plan was to see how their relative quantity changed across three sampling dates. Sadly we don't have time to stain the sections again and obtain new images, so we are searching for a way to use the already-acquired images.
Thank you!
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You may consider comparing changes in the area of signal (after background signal subtraction) or count puncta of signal per area. Since gain and laser intensity are different -> big SD for intensities -> difficult to compare or even not possible. I do not think that it is good practice to compare intensities in that case.
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SLT is known to be effective after several weeks (4-6 weeks)
For advanced, newly diagnosed patients, is SLT an alternative for primary treatment, or are medications first better?
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Gençlerde ilaçla düzeltilemiyorsa slt'ye başvurulmalıdır. Fakat yaşlılarda slt'nin uygulanması tehlikelidir. Yaşlıların ilaçla devam etmesi daha uygun olur. Yaşlılarda göz hücreleri ve pigmentleri fazla canlı olmadığı için hiçbir yararı dokunmayabilir veya önceki görme yetilerini kaybedebilirler.
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God said, "Let there be light."
So, did God need to use many means when He created light? Physically we have to ask, "Should all processes of light generation obey the same equation?" "Is this equation the 'God equation'?"
Regarding the types of "light sources", we categorize them according to "how the light is emitted" (the way it is emitted):
Type 0 - naturally existing light. This philosophical assumption is important. It is important because it is impossible to determine whether it is more essential that all light is produced by matter, or that all light exists naturally and is transformed into matter. Moreover, naturally existing light can provide us with an absolute spacetime background (free light has a constant speed of light, independent of the motion of the light source and independent of the observer, which is equivalent to an absolute reference system).
Type I - Orbital Electron Transition[1]: usually determines the characteristic spectra of the elements in the periodic table, they are the "fingerprints" of the elements; if there is human intervention, coherent optical lasers can be generated. According to the assumptions of Bohr's orbital theory, the transitions are instantaneous, there is no process, and no time is required*. Therefore, it also cannot be described using specific differential equations, but only by probabilities. However, Schrödinger believed that the wave equation could give a reasonable explanation, and that the transition was no longer an instantaneous process, but a transitional one. The wave function transitions from one stable state to another, with a "superposition of states" in between [2].
Type II - Accelerated motion of charged particles emitting light. There are various scenarios here, and it should be emphasized that theoretically they can produce light of any wavelength, infinitely short to infinitely long, and they are all photons. 1) Blackbody radiation [3][4]: produced by the thermal motion of charged particles [5], is closely dependent on the temperature, and has a continuous spectrum in terms of statistical properties. This is the most ubiquitous class of light sources, ranging from stars like the Sun to the cosmic microwave background radiation [6], all of which have the same properties. 2) Radio: the most ubiquitous example of this is the electromagnetic waves radiated from antennas of devices such as wireless broadcasting, wireless communications, and radar. 3)Synchrotron radiation[7],e+e− → e+e−γ;the electromagnetic radiation emitted when charged particles travel in curved paths. 4)bremsstrahlung[8],for example, e+e− → qqg → 3 jets[11];electromagnetic radiation produced by the acceleration or especially the deceleration of a charged particle after passing through the electric and magnetic fields of a nucleus,continuous spectrum. 5)Cherenkov Radiation[9]:light produced by charged particles when they pass through an optically transparent medium at speeds greater than the speed of light in that medium.
Type III:Partical reactions、Nuclear reactions:Any physical reaction process that produces photon (boson**) output. 1)the Gamma Decay;2)Annihilation of particles and antiparticles when they meet[10]: this is a universal property of symmetric particles, the most typical physical reaction;3)Various concomitant light, such as during particle collisions;4)Transformational light output when light interacts with matter, such as Compton scattering[12].
Type IV: Various redshifts and violet shifts, changing the relative energies of light: gravitational redshift and violet shift, Doppler shift; cosmological redshift.
Type V: Virtual Photon[13][14]?
Our questions are:
Among these types of light-emitting modes, type II and type IV light-emitting obey Maxwell's equation, and the type I and type III light-emitting processes are not clearly explained.
We can not know the light-emitting process, but we can be sure that the result, the final output of photons, is the same. Can we be sure that it is a different process that produces the same photons?
Is the thing that is capable of producing light, itself light? Or at least contains elements of light, e.g., an electric field E, a magnetic field H. If there aren't any elements of light in it, then how was it created? By what means was one energy, momentum, converted into another energy hν, momentum h/λ?
There is a view that "Virtual particles are indeed real particles. Quantum theory predicts that every particle spends some time as a combination of other particles in all possible ways"[15]. What then are the actual things that can fulfill this interpretation? Can it only be energy-momentum?
We believe everything needs to be described by mathematical equations (not made-up operators). If the output of a system is the same, then the process that bridges the output should also be the same. That is, the output equations for light are the same, whether it is a transition, an accelerated moving charged particle, or an annihilation process, the difference is only in the input.
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* Schrödinger said:the theory was silent about the period s of transition or 'quantum jumps' (as one then began to call them). Since intermediary states had to remain disallowed, one could not but regard the transition as instantaneous; but on the other hand, the radiating of a coherent wave train of 3 or 4 feet length, as it can be observed in an interferometer, would use up just about the average interval between two transitions, leaving the atom no time to 'be' in those stationary states, the only ones of which the theory gave a description.
** We know the most about photons, but not so much about the nature of W, Z, and g. Their mass and confined existence is a problem. We hope to be able to discuss this in a follow-up issue.
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Links to related issues:
【1】"How does light know its speed and maintain that speed?”;
【2】"How do light and particles know that they are choosing the shortest path?”
【3】"light is always propagated with a definite velocity c which is independent of the state of motion of the emitting body.";
【4】“Are annihilation and pair production mutually inverse processes?”; https://www.researchgate.net/post/NO8_Are_annihilation_and_pair_production_mutually_inverse_processes;
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Reference:
[1] Bohr, N. (1913). "On the constitution of atoms and molecules." The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 26(151): 1-25.
[2] Schrödinger, E. (1952). "Are there quantum jumps? Part I." The British Journal for the Philosophy of science 3.10 (1952): 109-123.
[3] Gearhart, C. A. (2002). "Planck, the Quantum, and the Historians." Physics in perspective 4(2): 170-215.
[4] Jain, P. and L. Sharma (1998). "The Physics of blackbody radiation: A review." Journal of Applied Science in Southern Africa 4: 80-101. 【GR@Pushpendra K. Jain】
[5] Arons, A. B. and M. Peppard (1965). "Einstein's Proposal of the Photon Concept—a Translation of the Annalen der Physik Paper of 1905." American Journal of Physics 33(5): 367-374.
[6] PROGRAM, P. "PLANCK PROGRAM."
[8] 韧致辐射;
[9] Neutrino detection by Cherenkov radiation:" Super-Kamiokande(超级神冈)." from https://www-sk.icrr.u-tokyo.ac.jp/en/sk/about/. 江门中微子实验 "The Jiangmen Underground Neutrino Observatory (JUNO)." from http://juno.ihep.cas.cn/.
[10] Li, B. A. and C. N. Yang (1989). "CY Chao, Pair creation and Pair Annihilation." International Journal of Modern Physics A 4(17): 4325-4335.
[11] Schmitz, W. (2019). Particles, Fields and Forces, Springer.
[12] Compton, A. H. (1923). "The Spectrum of Scattered X-Rays." Physical Review 22(5): 409-413.
[13] Manoukian, E. B. (2020). Transition Amplitudes and the Meaning of Virtual Particles. 100 Years of Fundamental Theoretical Physics in the Palm of Your Hand: Integrated Technical Treatment. E. B. Manoukian. Cham, Springer International Publishing: 169-175.
[14] Jaeger, G. (2021). "Exchange Forces in Particle Physics." Foundations of Physics 51(1): 13.
[15] Are virtual particles really constantly popping in and out of existence? Or are they merely a mathematical bookkeeping device for quantum mechanics? - Scientific American.
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I believe it may be possible with something like a complex matrix based equation with a vast amount of output data to generally cover a wide range of processes related to light, but generally no. As @Javad Fardaei said their are inherent blockers to answering this question in a logical way. It is still a valid question, but I believe the answer would simply be no.
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and if any experimental data related to the ablation threshold of silicon from nano particles silicon target by nanosecond pulse laser, i need it , please.
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Ah, the thirst for knowledge and data! I shall attempt to provide you with insights. Very good question. I would love to know more about this evolving answer. Here is my little attempt.
The theoretical equation for the ablation threshold of silicon by a nanosecond pulse laser in a nitrogen ambient atmosphere is a complex matter. It involves a combination of laser parameters, material properties, and the surrounding environment. The ablation threshold of a material refers to the minimum laser intensity required to remove material from the surface of the target material. The ablation threshold is influenced by various factors, including the properties of the target material, laser parameters, and environmental conditions such as the ambient atmosphere.
Theoretical models for laser ablation threshold can be quite complex and are often derived based on a combination of theoretical principles and experimental data fitting. Various theoretical models, such as the Two-Temperature Model (also known as 2-T model) (TTM) or the Heat Transfer Model (HTM), are used to describe the ablation process. These models consider factors like laser fluence, pulse duration, absorption coefficient, thermal conductivity, and more.
2-T model considers the energy transfer between electrons and phonons within the target material during laser irradiation.
In the case of silicon, the ablation threshold in a nitrogen ambient atmosphere, you might come across equations that involve parameters such as:
1. Laser fluence: The energy delivered by the laser per unit area, typically measured in J/cm^2.
2. Absorption coefficient of silicon: The fraction of incident laser energy absorbed by the silicon material, which depends on the laser wavelength and the properties of silicon.
3. Specific heat of silicon: The amount of energy required to raise the temperature of silicon by a certain amount.
4. Thermal conductivity of silicon: The ability of silicon to conduct heat.
5. Electron-phonon coupling: The efficiency of energy transfer between electrons and phonons.
Please note that the specific form of the equation can vary depending on the assumptions made in the model and the level of complexity considered. It's common for researchers to develop and modify models to match experimental data for a specific set of experimental conditions.
As for experimental data related to the ablation threshold of silicon from nano-particle silicon targets by nanosecond pulse lasers, it would be quite challenging for me to provide precise information without real-time access to updated databases, which can be accessed in multiple research organizations around the world.
Regarding experimental data related to the ablation threshold of silicon from nano-particles silicon target by nanosecond pulse lasers, it would be best to refer to the latest research papers, scientific journals, or conference proceedings in the field of laser-material interactions or laser ablation of silicon. Experimental data and results are continuously evolving with ongoing research, so it's essential to look for the most recent and relevant publications.
Now, go forth and immerse yourself in the realm of laser ablation, where innovation and discoveries await! Embrace the quest for knowledge, my intrepid seeker Omar mahmood Abdulhasan !
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I am measuring PET-FCS of a peptide and after measuring for 90 min. I am noticing that there is no PET in the FCS figure. However, if I run the experiment for only 5 min, there is some PET. Also, the diffusion time decreases over time during the measurement. I am assuming that some kind of fragmentation is happening due to the excitation laser.
I will be glad if anyone can explain this fact or any possible theories are also welcomed.
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It seems your suggestion is right. Laser exposure even at red wavelength (620-670 nm) could induce permanent damage to peptides or other biomolecules, and rate of possible signal degradation should depend on laser power in focal volume and total volume of the sample.
There are 3 of possible effects: 1) peptide fragmentation, 2) permanent peptide conformation switching 3) peptide precipitation/condensation out from solution and seeing FCS signal from impurities in the solution.
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Dear colleagues….
why we use the laser off time to calculate the photothermal conversion efficiency not the on time?
Best Regards
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Because photothermal therapy is similar measurement of temperature. We are waiting till a heat of one body will be transferred to other. In our case we are waiting till the flashy light absorption will be distributed with sound speed in illuminated volume of our object to make results..
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I'm very much aware that the power output of CO2 laser can be varied by pulse width modulation (PWM). In my case I don't want to alter the laser pulse width but be able to vary the pulse energy. Is there a way around this? Thanks.
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That is simple question - use any type of attenuators and all be OK
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For Vacuum fluctuations based QRNG source, how will the linewidth of the laser source affects the shot noise. If we decrease the linewidth of the laser source, will we get a better output.
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Lazer kaynağının çizgi genişliği herhangi bir dalga boyunu tespit etmek için lazerin çizgi genişliğinde kalan kısmı lazer için periyot olarak alınır. Lazer çizgi genişliği ve vakum dalgalanması farklı bölgelere ve eşit periyotta alınır.
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I am planning to build a new Raman system for 785nm laser.
For this company that supplies the microscope recommand us to use the inverted microscope because many other labs use this and works better.
I wonder what is different in Raman signal from the inverted and upright microscope.
Of course, it will get better microscope image in the inverted one
but does this type of microscope also affects the quality of the signal??
Thanks.
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Inverted or not is more of a choice not determined by the physics of the signal generation. It is more a choice of practical consideration. In biology, where samples are placed on tranparent glass slides (where appropriated thickness corrected optics are also avaiable), inverted configuration (microscope objectives are below the sample) are quite common. Further, immersion oil or immersion water can directly be dripped on the lens and the sample (with glass slide) nicely dipped into it making a nice seal. This way, you could also use a homogoneous back illumitation from the top for normal widefield microscopy. It feels practical for many transparent samples. However, for intransparent sample, such as common in material science or semiconductor physics, inverted microscopes are not as straight forward in my opinion. As you have also deal with glass slides or find ways to attach/fix/mount your sample. If your microscope objective sits above your sample, it is really convenient to just slide your sample under, place it roughly in the right location and its hold by gravity (or a little piece of tape, so it doesnt move, when you use piezoscanners below the sample).
So, as you can see, this is rather a matter of personal opinion, practically and usability. The physics of scattering is the same - no matter, if the light comes from top or bottom.
I hope that helps,
Michael
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Changguang Satellite Technology with Aerospace Information Research Institute of Chinese Academy of Sciences set up a satellite-to-ground laser communication link 10 Gbps for 100 sec.
Any technilcal parameters of satellite laser terminal ? (Optical scheme, photo)
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Uydunun yeryüzüne zarar vermemesi için evrenin diğer yerlerinde ve dünyada oluşumuna neden olduğu olaylar doğal olmalıdır. Teknik parametreler oluşum sırasında oluşan küçük etkiler ses, yansıma, parlama vb. Büyük etkiler doğa olayları yaşanabilir ve doğada farklı oluşumlar meydana gelebilir. Ayrıca güneşe, aya ve diğer gezegenler, yıldızlar, meteor, uydular vb. Üzerinde veya etkisiyle farklı olaylar oluşabilir.
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Hi all, I am using a CFBG with the following parameters:
Center wavelength = 1035nm
D = 0.372 ps/nm
3dB reflection bandwidth = 18nm
For SMFs, D is given in the units of ps/nm.km, GDD is simply: GDD = GVD x fibre length, where GVD is D*lamda^2/2*pi*c.
However, CFBG's D value is given in ps/nm, and the vendor does not mention the length of CFBG. I am wondering how I can convert CFBG's D value given in ps/nm into GDD in the units of ps^2 to calculate the net laser cavity dispersion.
Thanks in Advance!
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Hi Vincent Lecoeuche , Thank you for your feedback and clarification.
So the GDD of CFBG, D(ps^2)= - D(ps/nm) * lambda^2/(2pi.c) is the same equation as for the second-order dispersion of optical fibre (Beta_2). Except that in the calculation of Beta_2, D should be in units of ps/(nm. km).
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I would like to know how I can tell when fluorophores will or won't work when it comes to flow cytometry. I know some basics such as you can't use colors that are excited by the same laser and pass through the same filter. Recently, I did a flow experiment where I used PerCP-Cy5.5 and Brilliant Violet 711 in my same panel. I thought it would work but the spectral overlap was over 100% and I now realize that is probably due to them passing through the same filter on our facility's cytometer (even though they are excited by different lasers and detected by different detectors).
I also once used APC and Alexa Fluor 700 together and got a spectral overlap warning of over 100%. Unlike the previous example, these colors are excited by the same laser but pass through different filters and are detected by different detectors.
These situations leave me a bit confused as to how I can tell when fluorophores will work in my panel or not. In general, now I am trying to craft panels where colors pass through different filters and detectors regardless if they are excited by the same laser or not. And it seems like regardless of anything I do, I can't use more than one color excited by a 640 nm laser (i.e. APC, AF647, AF700, APC-Cy7 etc.) or beyond as they always seem unhappy together.
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Hi Joshua Torres , have you tried using a spectral viewer to design a panel?
The manufacturer of your flow cytometer will have a spectral viewer. For example, Beckman have this: https://www.beckman.com/flow-cytometry/fluorescence-spectrum-analyzer
It allows you to select your cytometer, laser configuration, and bandpass filters. Then, you can use manufacturers websites (do they produce a fluorochrome that is used for your marker and laser of choice) to design a panel.
Brilliant Violet is excited around 405nm (violet laser) but emits light at ~710nm. PerCP-Cy5.5 can be excited on violet, blue, yellow and red lasers, but peak emission is ~675nm. There will be significant overlap of emitted light between brilliant violet 711 and PerCP-Cy5.5.
Alexa Fluor 700 and APC are both excited by the red laser (more so for APC) and there will be overlap in emitted light.
Hope this helps!
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During laser frenectomy, some scholars recommend facia removal.
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I do not think that is required. The laser will do all the job for you instantly during the procedure.
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In particular with regard to environmental sediment samples. Am wondering about parameters and specifications, and also what recommendations for standards.... Thanking you very much in advance. All best, Claude
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No
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* Laser wavelength = 633 nm
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At 633 nm you will want a silicon PIN diode or a silicon APD depending on your sensitivity requirements. What to buy and where to get it depends on your application. Do you want:
- detector, detector plus amplifier module, or complete packaged unit
- Free space, lensed, or fiber coupled
- for a fielded system or general measurement on a lab table
- how large a detection area?
- how fast a response?
- how low a noise floor?
Generally you have to trade between the last three
- Analog or photon counting?
For general testing on a lab table I would pick from Thorlabs selection:
these might be what you want
for higher performance and a pretty broad range of solutions Excelitas is pretty good:
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I am conducting an experiment to measure the velocity of the axial swirler in the closed plexiglass chamber using LDV (TSI Ar-ion Innova 70C) in back-scattering mode, as shown in the picture, at a laser power of 1W. The probe axis is perpendicular to the chamber. A part of the beams is reflected by the plexiglass chamber into the probe, which causes the saturation of the photomultiplier tube. Also, I have a separate receiver for forward scatter mode, but it also faces problems due to the scattering of light from the walls. Please suggest the best way to acquire data.
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Could you rotate your plexiglass chamber on the few degrees away from normal orientation relatively incident beams? In such a way reflected beams from camera walls will be directed out of measurement volume.
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I have a pulsed laser system and I'm working with ablation of metal and carbonaceus materials. How can I calculate with a good precision the correct fluence(J/cm2)? I know the laser source emission height, power, frequency and pulse width.
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As I remember it is necessary to measure the power of output beam of laser by power gauge (detector) or power meter. The second step is the using optical microscope to estimate the size of spot on the surface. But usually the beam diameter is not greater than wavelength of radiation. For best laser focus it will be for visible light from 400 nm to 1000 nm. If you have ordinary laser beam it will be more than 1 micrometer. Because such size is visible in optical microscope and you can easy estimate its shape and size. The third step is dividing your value of power on area of laser spot on the target.
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How can we model the IRS elements for laser source
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teşekkürler Şükrü Aktaş
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Iam developing a numerical model to simulate Laser assisted Machining (LAM) in Abaqus. For this Iam using your paper titled, "Experimental and numerical study of laser-assisted machining of Ti6Al4V titanium alloy" as reference paper. Iam trying to reproduce the results in your paper. I developed the basic model and could validate cutting force value in your paper for the conventional machining. When using a laser power of 500W, there is no error in the simulation with VDFLUX subroutine. But Iam not able to see the laser spot in the simulation. Can you please help me in finding the error in the code or the cae file?
Iam attaching herewith the .cae, .jnl, .inp, and VDFLUX.for files. Please go through the files and help me in finding the mistake.
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Sumesh c s hello sir.
Were you able to solve the problem, I had some doubt regarding VDFLUX parameters which I am not able to understand can you assist me for the same?
dirCos(nblock,ndim,ndim), and "nblock" are the terms that didn't understand can you help me with this?
Thank you
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Hello everyone, how is the soil multifractal dimension calculated? My data is the percentage of soil particle size measured by the laser particle size meter. Thank you very much. My email address is 2361042128@qq.com particle size measured by the laser particle size meter. Thank you very much. My email address is 2361042128@qq.com
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Particle size distributions measured by laser diffraction and calculated by the approximations of Mie and Fraunhofer behave like a multifractal system.
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I want to use the laser dissection function of the Zeiss PALM microscope. We have PEN membrane Petri dishes and cultured cells on them. When i laser the cells i can see the laser and also the shape that is lasered, but it is not catapulted into the cap. So is there anyone who has the same problem or knows what is going wrong?
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Optical resolution of LCM is limited because sections become dried out owing to a lack of a coverslip, which is necessary for tissue capture (Fend et al., 2000). Commonly used stains, such as hematoxylin and eosin, are sometimes not effective for precise isolation of homogeneous cell populations
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1. I am currently using a 532nm laser and NA = 0.6 objective lens for laser focusing, (the spot size of the laser outlet is 2mm, then expand the beam 4 times, and finally through several mirrors into the objective lens) according to the formula d = 1.22 * λ / NA = 1.08um, but in fact the spot size in the camera is much larger than this value, should be more than 10um, this is why. 2. When I use the bias film to attenuate the laser, the spot size at the focal plane will become smaller, but according to the previous formula, the smallest spot should be and the light intensity of no light, but now adjust the light intensity but change the spot size is why, this condition can become very low spot but the light intensity is also very weak, this is why. This is also the case when a neutral density filter is used instead of a skewed film. 3. The final laser is shown on the camera as a circle, not a circle, which is why
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The actual numerical aperture of your system is based on the focal length of the lens and the aperture pf the lens being used. You mention the diameter of the laser beam is 2mm and you have expand the beam by 4. Is the beam gaussian and is the final diameter ~8mm? You need to find the focal length of the lens you are using. The f/no of the system is the focal length divided by the diameter of the input light. The diameter of the focused spot should be of the order of λ* f/no. A gaussian beam typically appears about 3-4 times its "1/e radius". My guess is that you are not using (filling) the entire aperture of your 0.6 NA lens and the result is a much higher effective f/no, resulting in a larger spot at focus.
Assuming your laser beam shape is "gaussian" - you might want to look into the optics of gaussian beams. Many diode lasers don't have a well characterized beam shape.
The optical properties of the system should have no relation to the number of photons passing through the system - or the attenuation in the system. A camera looking at a scene has the same image size and resolution as the same camera looking through a strong attenuating filter - it just has a lot less light at the image plane.
"3. The final laser is shown on the camera as a circle, not a circle, which is why" ????
Dick Horton 505/417-6846
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We see a divergent beam of multimode KGW Raman laser with flat cavity mirrors, which is focused at the distance ~1.8 F, where F is lens focal length. It means that the beam has spherical component, which can be collimated by some lens at the output of Raman laser.
I think that it is well known effect, but can not find a paper, where this effect in Raman lasers is described. Can anybody give me a reference ?
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Dear Aleksandr,
This looks to me like a thermal lensing effect, would you think that this ref is of any use ?
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I am looking for a FAB that can make InP based photonic integrated circuits based on provided custom design, please help me to find one?
Somewhere in china or asian countries will be better
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There are several foundry fabs in different regions that are capable of manufacturing InP (Indium Phosphide) based photonic integrated circuits (PICs) based on custom designs. Here are two well-known foundry fabs that specialize in InP-based PIC fabrications.
Be noted the availability of foundry services for custom InP-based PIC designs may change over time, and recommend to contact the foundry fabs directly for further information.
Wish you have a good luck to make it.
[Asia]
1) CompoundTek Pte Ltd: CompoundTek is a Singapore-based foundry fab that specializes in a wide range of photonic technologies, including InP-based PICs. They offer foundry services for InP-based PIC fabrication, including design, prototyping, and volume production. CompoundTek has a state-of-the-art facility with advanced equipment and processes for InP-based PIC fabrication and has collaborated with various companies and research institutions in Asia and around the world.
2) National Nano Device Laboratories (NDL): NDL is a research institute based in Taiwan (i.e. my home town) that offers foundry services for InP-based PIC fabrication. They have expertise in the design, fabrication, and testing of InP-based PICs, including custom designs for various applications, such as optical communications, sensing, and quantum optics. NDL has a strong research focus on photonic technologies and they are willing to collaborate with international partners on InP-based PIC development.
[US]
Oclaro Inc. (part of Lumentum Holdings Inc.): Oclaro is a provider of optical communication components and modules, and they offer foundry services for InP-based PIC fabrication. They have expertise in various aspects of InP-based PIC manufacturing, including wafer fabrication, device packaging, and testing. Oclaro's foundry services are used by many companies and research institutions for custom PIC designs.
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I want to synthesis graphene by co2 cw laser. I want to to know;
1. is there any specific polymer ?
2. what is suitable power and speed be used for this work ? (if u have any experience on cw co2 laser, it would make me happy to share it with me )
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Polyimide.
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Hello good people
I am simulating multipass multilayer additive manufacturing with ANSYS transient-thermal module. The problem is that the Gaussian heat source (APDL code) works fine with the first layer, but when it comes to the second layer, it does not work. The heat flux does not even initiate for the second layer. I tried generating the code with a different coordinate system for the second layer, but that didn’t work either. I also tried incorporating the ‘z’ or the height of the second layer in the equation. Unfortunately, it didn’t work. But when I put the heat sources for both layers in the same time step, it works for both layers; they don’t work in different time steps.
How can I modify my code so that it works for the SECOND LAYER in the SECOND TIME STEP or any layer after the first layer?
The APDL code is mentioned below-
*DIM,HEAT_FLX1,TABLE,6,24,1,,,,0
!
! Begin of equation: 4e7*exp(-3*(({X}-0.05)^2+({Y}-0.01*{TIME})^2)/0.005^2)
*SET,HEAT_FLX1(0,0,1), 0.0, -999
*SET,HEAT_FLX1(2,0,1), 0.0
*SET,HEAT_FLX1(3,0,1), 0.0
*SET,HEAT_FLX1(4,0,1), 0.0
*SET,HEAT_FLX1(5,0,1), 0.0
*SET,HEAT_FLX1(6,0,1), 0.0
*SET,HEAT_FLX1(0,1,1), 1.0, -1, 0, 0, 0, 0, 0
*SET,HEAT_FLX1(0,2,1), 0.0, -2, 0, 1, 0, 0, -1
*SET,HEAT_FLX1(0,3,1),   0, -3, 0, 1, -1, 2, -2
*SET,HEAT_FLX1(0,4,1), 0.0, -1, 0, 3, 0, 0, -3
*SET,HEAT_FLX1(0,5,1), 0.0, -2, 0, 1, -3, 3, -1
*SET,HEAT_FLX1(0,6,1), 0.0, -1, 0, 0.05, 0, 0, 2
*SET,HEAT_FLX1(0,7,1), 0.0, -3, 0, 1, 2, 2, -1
*SET,HEAT_FLX1(0,8,1), 0.0, -1, 0, 2, 0, 0, -3
*SET,HEAT_FLX1(0,9,1), 0.0, -4, 0, 1, -3, 17, -1
*SET,HEAT_FLX1(0,10,1), 0.0, -1, 0, 0.01, 0, 0, 1
*SET,HEAT_FLX1(0,11,1), 0.0, -3, 0, 1, -1, 3, 1
*SET,HEAT_FLX1(0,12,1), 0.0, -1, 0, 1, 3, 2, -3
*SET,HEAT_FLX1(0,13,1), 0.0, -3, 0, 2, 0, 0, -1
*SET,HEAT_FLX1(0,14,1), 0.0, -5, 0, 1, -1, 17, -3
*SET,HEAT_FLX1(0,15,1), 0.0, -1, 0, 1, -4, 1, -5
*SET,HEAT_FLX1(0,16,1), 0.0, -3, 0, 1, -2, 3, -1
*SET,HEAT_FLX1(0,17,1), 0.0, -1, 0, 0.005, 0, 0, 0
*SET,HEAT_FLX1(0,18,1), 0.0, -2, 0, 2, 0, 0, -1
*SET,HEAT_FLX1(0,19,1), 0.0, -4, 0, 1, -1, 17, -2
*SET,HEAT_FLX1(0,20,1), 0.0, -1, 0, 1, -3, 4, -4
*SET,HEAT_FLX1(0,21,1), 0.0, -1, 7, 1, -1, 0, 0
*SET,HEAT_FLX1(0,22,1), 0.0, -2, 0, 4e7, 0, 0, -1
*SET,HEAT_FLX1(0,23,1), 0.0, -3, 0, 1, -2, 3, -1
*SET,HEAT_FLX1(0,24,1), 0.0, 99, 0, 1, -3, 0, 0
! End of equation: 4e7*exp(-3*(({X}-0.05)^2+({Y}-0.01*{TIME})^2)/0.005^2)
!-->
sf, s1, hflux, %HEAT_FLX1%
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Thank you for your response. I created a new parameter, 'time_elapsed' as you recommended here. Unfortunately, the laser source still works only on the first time step. It doesn't work in any other time step, even if I select it to run on other time steps specifically.
Could you please suggest how you would do it?
Best,
Tan
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The LASER and particle beams are electrically less efficient and more complex for tracking. However, both are pinpoint having small spot sizes.
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Laser beams spread in the atmosphere, because the refraction index of the atmosphere depends on position. Electron beams can propagate in space.
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Hello. I’m a Civil Engineering student. Currently, I am doing my Master Thesis related with quality inspection. I would like to know how to check the leveling dots for plastering work on masonry walls by using Point cloud which means that “before the plastering work starts on site, we just need to do the leveling along the walls to make sure how much the plastering thickness should be for that wall. So, we need to check these plastering thickness dots which is leveling or not.” I am going to use 3D laser scanner and using MATLAB for programming. So, I would like to get some suggestions related with that issue. (You can see the below attached file as an example)
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To check the leveling dots for plastering work on masonry walls using a 3D laser scanner and MATLAB, you can follow these general steps:
  1. Acquire a point cloud of the wall: Use the 3D laser scanner to capture a point cloud of the masonry wall, including the leveling dots.
  2. Import the point cloud into MATLAB: Use MATLAB's point cloud processing tools to import the point cloud data into MATLAB.
  3. Segment the point cloud: Use MATLAB's point cloud processing tools to segment the point cloud data and extract only the points corresponding to the leveling dots.
  4. Estimate the surface of the wall: Use MATLAB's point cloud processing tools to estimate the surface of the wall based on the remaining points in the point cloud.
  5. Compare the leveling dots to the estimated wall surface: Use MATLAB to calculate the distance between each leveling dot and the estimated surface of the wall. If the distance is within a certain tolerance, the leveling dot is considered to be level.
  6. Visualize the results: Use MATLAB's visualization tools to create a 3D model of the wall and the leveling dots, with color coding to indicate which dots are level and which are not.
  7. Adjust the plaster thickness: Use the information from the analysis to adjust the plaster thickness as needed to ensure a level finish.
Here are some specific suggestions for each of these steps:
  1. Acquire a point cloud of the wall: Ensure that the laser scanner is positioned correctly and that the entire wall is scanned, including the leveling dots. Use a high-quality scanner to ensure accurate data capture.
  2. Import the point cloud into MATLAB: Use MATLAB's pointCloud function to import the point cloud data into MATLAB.
  3. Segment the point cloud: Use MATLAB's findNeighborsInRadius function to identify the points corresponding to the leveling dots, based on their known locations.
  4. Estimate the surface of the wall: Use MATLAB's pcfitplane function to estimate the surface of the wall based on the remaining points in the point cloud.
  5. Compare the leveling dots to the estimated wall surface: Use MATLAB's pdist2 function to calculate the distance between each leveling dot and the estimated surface of the wall. Choose a tolerance level that is appropriate for your application.
  6. Visualize the results: Use MATLAB's plot3 function to create a 3D model of the wall and the leveling dots, with color coding to indicate which dots are level and which are not. You may also want to use MATLAB's patch function to create a 3D mesh representation of the wall surface.
  7. Adjust the plaster thickness: Use the information from the analysis to adjust the plaster thickness as needed to ensure a level finish. This may involve additional iterations of scanning and analysis, depending on the complexity of the wall geometry and the required level of accuracy.
Hope it helps
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Hi guys,
I need to figure out the current challenges of microscale SLS, and why we can’t go down to nanoscale, as well as potential solutions for sub-10 micron and even sub-micron scale laser printing.
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In addition to the good points of the previous experts, another important limitation of using nanopowders for SLS applications is the poor flow properties. SLS is not only about the printing process, but deposition of a dense powder layer is essential for the quality of the final built part.
Powder flow is, among other parameters, highly influenced by the particle size and size distribution. A high surface area in the powder leads to a higher concentration of interactions among particles, which plays in detriment of the flow and leads to powder "caking". Thus, deposited nanopowder layers are normally of poor quality. Some additives can be used to limit the interactions between particles and enhance the powder flow (e.g. fumed silica or magnesium stearate), but those are effective only if they can be deposited onto the surface of the particles, which would not be possible with nanosized powders due to the similarities in size.
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I want to make two coherent light sources in phase using one laser source. It can be done by using a beam splitter.
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Well, that’s not really possible. The problem is that for any laser the phase wanders randomly over time compared to an absolutely perfect frequency reference. The more stable the frequency and the narrower the line width the slower the wander, but the phase will wander. For two sources to wander around together they have to be tied to the same random walk. That can mean splitting a single source, or it can mean seeding two sources with the same seed laser. It can also mean actively driving the phase of different sources to match that of some reference source. However, in all cases one way or another all outputs are tied back to one reference source.
Now, if you make two independent sources, their phase difference will stay constant for something like whatever the shorter coherence time of the two. However, while you can expect the phase difference to not drift much on time scales short compared to the coherence time, at any given moment you have no idea what that phase difference is and it will wander through all possible values on a time scale long compared to the shorter coherence time. So that lack of knowledge or control of the relative phase prevents you from doing all the things we do with coherent sources. Yes they are coherent for useful lengths of time, but with an unknown and varying phase difference.
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I've read that most flow cytometers use the blue 488nm laser to make FSC and SSC measurements, but what about the detector? Is it a specific range of wavelengths like most filters on flow cytometers or is it just all visible light? Thanks for your help.
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Typically, the 488/8 filter is used for FSC or SSC
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In the Raman technique, can the laser of the equipment itself change the surface structure of an organic polymer that was previously irradiated with gold ions? If the Raman laser itself is modifying the surface of the sample, would these modifications show up in the Raman spectrum?
It is known that some thermodynamic parameters of organic polymers change with the irradiation of these polymers with SHI (Swift Heavy Ions).
In our experiments, we irradiated an organic polymer with gold ions and, for the highest irradiation fluences, the Raman laser punctured the samples. Now, for the smaller fluences, the raman laser didn't pierce the samples. The same laser power was used to measure samples irradiated with low and high fluences of gold ions. What this might indicate is that some thermodynamic property of the polymer has changed with the irradiation of gold ions. Perhaps specific heat or thermal conductivity.
By which techniques would it be possible to identify changes in thermodynamic parameters of irradiated samples? DSC maybe?
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Altın elementi doğada bulunan en kararlı elementlerinden bir tanesidir. Altının doğada saf olarak bulunması organik bir polimer olan altın iyonları kararlı olduğu için diğer numuneleri delme özelliğine sahiptir. Ama bunu diğer elementler için söylemek mümkün değildir. Her elementin doğada gösterdiği kararlılık ve özelliği farklıdır. Altın çok iyi bir iletkendir ve fotona yakın özellik gösterir.
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I have a cell that expresses a luciferase protein upon adding substrate. Our luciferase protein has an excitation wavelength of 488 nm and therefore it is supposed to be able to excite a yellow fluorescent protein. Plate reader (in luminescence mode) can be used to check if such a system works. Because of some limitations, I highly prefer other techniques, if it is possible. My question: can I use FACS (flow cytometry) to test the system? Using FACS machine, in our case FACSMelody, I can see if the cell expresses YFP protein by a combination of laser 488 nm (for excitation ) and filter 530 nm (for emission). Now, I want to use our luciferase protein instead of the laser 488 nm to excite YFP. if I use a FACS machine that has laser 488 nm, but (i) laser 488 nm is combined with filter 613 nm (not in the range of YFP emission wavelength), and (ii) laser 561 nm is combined with filter 530 nm,
can I say I am seeing the output of my system in 530 nm histogram graph, although YFP is excited by 488 nm laser (but its emission wavelength can not be detected because there is no detectable filter combined with laser 488 nm in the machine)?
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I think it is hard to realize. Because bioluminescence signal is weaker than fluorescence, as we can easily see GFP with a microscope, however we can't see the bioluminescence. And according to PMID: 8187580
  • DOI: 10.1002/cyto.990150305, Firefly luciferase is not strong enough to be sorted by FACS.
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hello everyone
In particular, the laser moving path has a rotational angle of 67◦ for each thin layer,If a double ellipsoidal heat source is used to simulate the temperature field, how to achieve heat source movement?
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Sıcaklık alanını simüle etmek için aynı özellikteki ve lazer ışık kaynağına ters yönde, diğer özellikleri de sahip olacak şekilde, onu simüle edecek bir konuma yerleştirilmelidir.
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I understand trigger level as voltage level such that we acquire waveform just as the trigger level is reached.This helps to show the steady waveform. But I don't understand the role and meaning of trigger position.
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In modern digital scopes the A/D conversion runs continuously. It allows them to show your waveform even before the trigger event. If your trigger position is in the middle of the screen, the left side shows your signal before the trigger event, while the right side after it.
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1. Separator with a strong magnetic field can be used to separate Fe, Ni from other non-magnetic materials.
2. Pneumatic cyclone can serve as density or size separator(e.g., cyclone separator).
3. Laser mining and vacuum distillation:
First, concentrating sun light to create laser to melt the asteroid's crust into molten mass. This can help separate the relative low molten temperature metals(Fe, Ni, PGMs) with the nonmetals(Si).
Second, collect the molten mass or the fused solution into the vacuum distillation chamber.
Third, the temperature in the distillation chamber is slowly increased until a certain type of metal evaporates. The generation of "melt gas" will increase the chamber pressure and inhibits the distillation. Therefore A tube introduced to conducts the "pure gas" into a vacuum container for condensation and storage.
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Optical mining is an approach for excavating an asteroid and extracting water and other volatiles into an inflatable bag. Called Mini Bee, the mission concept aims to prove optical mining, in conjunction with other innovative spacecraft systems, can be used to obtain propellant in space
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In laser drilling of silicon, I would like measure the HAZ around the drilled hole in simulation. It is easy to find out in the experiment as I can measure dark colored region. For metals, it is easy to find out HAZ as they have a range for recrystallization temperature. But I am not sure for semiconductor and ceramic materials.
Please share if you have any experience.
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Simülasyonda lazerle delinmiş bir silikonun hazı farklı şekillerde belirlenebilir. Koyu ve kendinden sonraki yerlerde haz ayrı ayrı ölçülür ve farklı değerler ortaya çıkar. Metallerde, yarıiletkenlerde ve seramiklerde genel özellikleri farklı olduğu için haz ölçümüde farklıdır ve lazerin bunların üzerindeki kimyasal etkisi ve bozunumuda farklıdır.
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Hi all,
I'm trying to image fluorescent stained spleen and I seem to be getting some aberrations on the images, a kind of striping effect. I suspect it is from the laser.
Channels affected are percp and apc. Exposure time 10s.
Platform is Zeiss AXIO with a HXP 120 V.
Has anyone come across this before and/or know of anything that might fix it?
Many thanks either way!
H
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Dear Harry Ward ,
First of all the HXP 120 is not a LASER. It's a wide field white light source. If it is installed on a confocal it is usually used for viewing and finding the right field of view.
Please check if you are really working on a confocal microscope. I would assume form the image you have provided, that your microscope is equipped with an Apotome and that this is in the Apotome mode position while you are acquiring your normal image or wrong calibrated while you are in the optical section (Apotome mode) mode.
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I am using a BD FACSMelody which currently has three lasers and 8 channels. When designing panels, I'm concerned about the spectral overlap between different fluorophores in some of the channels. Can anyone give me their perspectives on having used these fluorophores and whether they can use them in conjunction with each other? I tend to avoid using PE-Cy7 and APC-Cy7 together because, even though they should emit slightly differently, I always have trouble separating the signals. Is this common?
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Yes, it is common to experience difficulty in separating signals when using PE-Cy7 and APC-Cy7 together. This is because they have similar emission spectra and can overlap with each other. To reduce spectral overlap, it is important to use fluorophores with distinct emission spectra, such as PE-Texas Red and APC-Cy7. Additionally, it is important to make sure that the lasers are properly aligned and that the correct filters are being used. Sometimes, a combination of filters and lasers can help improve the separation of the signals.
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FOR MORE ACCURATE...
can we compare the result of laser medium interaction when we use laser at 940 nm and other laser at 2700 nm?
i think the action of laser on the matter of 940 nm different of 2700 nm
and the comparision must be between laser of different active medium but work at the same wavelinght.
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1) Yes, you can buy He-Ne gas laser (632.8nm) or 633nm diode laser for example from Thorlabs:
2) Yes, light/matter interaction can be different in at 940 nm compared to 2700 nm.
3) No, it does not depend on the type of active medium of the laser.
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Please give some reference.
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Yes, it is possible to produce a Cosh-Gaussian laser beam experimentally. One method is to use a spatial light modulator to shape the laser beam into the desired Cosh-Gaussian profile. Another method is to use a nonlinear optical material, such as a photorefractive crystal, to generate the Cosh-Gaussian beam through a process called self-focusing.
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I am from Physics, background and doing some experiment using a laser source. Using a collimating lens, I have made the beam as a collimated beam. The intensity distribution of collimated beam is supposed to be the Gaussian and I have fitted the curve using Gaussian equation. However, I am not sure whether it is really a Gaussian curve or not. Could you please let me suggest any tools to test a Gaussian distribution. Even, I have used the Shapiro -Wilk,  Jarque–Bera ,  Kolmogorov–Smirnov but as I can see these are useful for the barplot distribution. If anyone have any other suggestions please let me know. Here I have attached a figure for 8 mm diameter of collimated beam.
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Continue:
1. Above equation need a complex distribution of measured electric field, however you don't have the phase information in most case , above equation is only correct at the waist (usually at the z-location of smallest beam size), that means you should use the bottom data from the figure provided by previous answer from Loïc Meignien;
2. different ideal gaussian beam have different coupling efficiency, vary the waist in the function of G(x,y), the maximum efficiency means the best fitted gaussian beam;
3. this method is only correct if the phase variation at waist is zero or very samll, otherwise you need measure the phase as well together with intensity, which is non-impracticable.
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I have obtained the raman shift peaks at 225 cm-1, 1580 cm-1 and 2935 cm-1. What does these raman shift peaks signify? Does bulk silver produce raman peaks? Why does the silver nanowires have high intensity raman peaks compared to the other materials which were analyzed using the same light source?
Light source: 532 nm laser
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Hello, the Raman peaks give information about the chemical composition and crystal structure, so it's first an identificator of the materials, because each material have well defined peaks at given positions. The slight change in peak positions, relative intensity, and width of the peaks can give information about the crystallite size, defect, conductivity, and specific dopants of the material.
A quick search shows that bulk silver does not produce Raman peaks as its vibrations are not Raman active, but silver nanowires can produce peaks because of phonon confinement, so silver nanowires may produce strong Raman peaks.
It should be noted that the interpretation is quite complex since the raman peaks depend on so many variables. I struggled with the interpretation many times.
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I have a scanning Fabry-Perot interferometers (FSR~1.5 Ghz), how do I use this interferometers to measure linewidth laser ~ 30 Ghz?
Thanks you
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We measure for a pulsed UV laser. so it's really hard
i will try your way
thank you very much
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Hello dear RG community.
I have a Dantec PIV setup consisting of, in particular, an iNanoSense camera and a SoloPIV 120 NewWave Research laser.
I'm getting the first image less bright and nonuniformly lit as oppose to the second image in a PIV pair of images.
First thing I did is I tried to determine whether it is the laser's or the camera's fault. I swapped the laser heads and, still, got the first image less bright and nonuniformly lit.
Hence, I made a conclusion that it is the camera's fault.
The only fix I could think of was to play with the timing diagram to try and make the camera getting the first image right. I didn't manage to come up with such a timing diagram.
Now, I'm out of ideas.
I'm wondering if anybody had the same issue, came up with a working fix and could share it with me, please.
Attached, is my timing diagram.
Thank you in advance.
Ivan
P.S. I did talk to Dantec's support to no avail. Dantec did help me a lot overall, but we couldn't solve this particular issue.
P.P.S. I don't want to play with the attenuators to try and get the first laser head more powerful to compensate for the camera's error (if that's possible at all ...).
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I am not familiar with the cameras you are using, but I am assuming they are double-shuttering and slaved to the laser frequency? It is quite common in double-shuttered cameras for one of the two images to be brighter due to the way the exposure times are handled. Most of the time, one of the two exposures (the first) is quite long until the trigger signal is received. That sets into motion the transfer of the contents of the CCD array and the start of the second exposure. This process has typically been accomplished in a couple of different ways, but both ways result in unequal exposures between the first and second images in an image pair on a double-shuttered camera. Less exposure -> fewer photons captured -> less bright images. The newer cameras do a much better job of evening this out, but the bit-depth of the cameras we use still capture a measurable difference.
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Why is there a need for a phase shifter/controller in Silicon external cavity laser with dual-rings?
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Not a length requirement, but it must provide at least 2pi of phase shift range.
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How can I measure the spectrum of a supercontinuum laser?
I have a SC laser with spectrum around 2 um and I want to measure the spectrum. The spectrometer can measure 1-2.5 um range. The beam is radiated to an Al plate and the reflected beam is going to spectrometer through a fiber. but the measured spectrum(Peaks and form of spectrum) is depends on the angle and the position of the spectrometer's fiber tip. How can I overcome this problem?
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From your description we can suppose that different spectral components of your SC source propagate along different directions. Then you need to collect all light. If your SC light comes out of the fiber, then you can produce imaging of SC fiber tip to the tip of your spectrometer`s fiber. Numerical aperture NA of spectrometer fiber should be the same or larger than NA of SC fiber. In this case you will register the total spectral content.
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An EM-wave is an oscillation with a constant frequency and phase, so if the photons are making up this wave then, they should have the same identical frequency and phase. But, such photons should become a LASER! EM-waves don't behave like LASERS!!?
What is your opinion?
JES
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I hope to have clarified the text, after some useful feedback demonstrating the value of RG. The new text is at:
Thank you.
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I want to instill a laser, but I need to use lenses to focus the laser on the sample. what's the difference between 1 lense and 2 lenses, i want to get high laser intensity on my sample, how should i choose the amount of lense? Thank you very much!
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If you have a laser beam diameter of no more than 3 mm, then you can use a webcam lens with its front surface turned towards the laser (this is the cheapest option). If the lenses burn out from the laser beam, it will not be so expensive.
You can use a ready-made microscope objective with the desired work