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Hello there,
I saw on some conventional BOTDA designs on the net that, they are using two different laser sources in BOTDA. Is that not more expensive than using one laser? Could be there another reason for this except for the difficulty of using loop design?
Thanks in advance,
Best Regards
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Hello!
To the best of my knowledge, I do not see any good reason to use two lasers except for the case you mention. In addition to the cost, the wavelength stability of the two lasers to keep and control the frequency difference is another significant challenge.
I can be wrong but I think that all commercial BOTDA and BOFDA use a single laser source.
Best regards,
Fabien.
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Hello. In real moment I'm designing the CPA system for my Ti:Sa laser. I have only cw diode module for pumping (10 W). How can I evaluate amplification opportunity in 'regen'. I want to gain from 1 nJ to 150 mkJ.
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Due to the short fluorescence lifetime of Ti:Sa, perhaps it is hard to get the gain in regenerative amplifier by such cw pumping.
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Dear colleagues ;
what is the spot size diameter required for a 808 nm laser power to ablate cancer cells in 96 wells ?
Best Regards
Huda
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2.5 W/cm2 and the duration is 5 min
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Hello All,
I have a question, what is a material of a (final) aperture were using in UV laser?
Mentioning related articles also will be great.
Best,
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The aperture and other elements are made from high-quality, low-absorption, excimer-grade fused silica and CaF2. These elements are AR coated and optically designed for narrowband or broadband wavelength ranges.
Manufacturer 👇
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Newton, New Jersey 07860
USA.
2)Photonics Media / Laurin Publishing Co., Inc.
100 West St.
PO Box 4949
Pittsfield MA 01202-4949
(413) 499-0514
fax: (413) 442-3180
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Dear Sir,
I have designed a Raman Spectromter but struggling with signal, Could you please help me in this Regards.
1. have designed Spectrogrpah and calbratd with Xe Ar lamps. working nice.
2. an objective lens is used to direct the laser light and collect the scattering from sample.
3. semrock make edge filter is used to remove laser line
only laser iine is appearing not a single hump of Raman spectra.
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The long pass will let a significant amount of the 785 nm laser with a 6 nm bandwidth though and will be at a much higher intesity than the Raman signal. You are seeing a big "baseline" spike in your spectrum (one with rhodamine) and that amount of light in the spectrometer gets scattered internally and creates a large background. What is your spectrometer and its specifications?
With a good notch filter and a laser designed for Raman spectroscopy you can look at the laser line and not have it swamp the Raman signal on either side.
There are a lot of details to getting a Raman signal that can bite you. Go through everything and eliminate all sources of stray light. Good luck.
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I'm doing molecular spectroscopy experiments in a UHV setup. Currently the laser passes through the experiment and I measure the laser energy with a Gentec powerhead after the exit window. However, normalizing my signal with the laser energy does not produce very good results. I would like to find a powerhead that is designed to be used in UHV that I can attach to some manipulator near the interaction region. Any ideas?
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Hi Adela,
I missed your response. Yes, I have measured the linearity of both the detector as well as the depletion of the ion beam with the power of the laser at several wavelengths. The issue is that day-to-day I cannot get consistent overlap of the ion/laser beams and the optical path is not well-aligned (old vacuum parts--I suspect one cross flange is bent by 1-2 degrees). The OPO laser beam is roughly 1x0.5 cm^2 and when scanning from UV to IR the most intense part of the beam walks around a bit. An iris aperture and a detector near the interaction region is my best idea of solving the issue.
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Laser ablation is an widely used technique for the synthesis of nanoparticles but it can also be used for preparation of nano-structures on the materials.
The nano structure so formed is called Laser induced periodic surface structure (LIPSS). There are many studies showing the mechanism of formation of LIPSS.
But is there any study on the effect of the thermodynamic properties and the crystal structure of the material on LIPSS.
Thank You
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@Yuri Mirgorod Thank you for you response Sir
I will follow up the article you mentioned.
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Are there any LASER fabrication group in USA where I can fabricate an antenna with 25 micrometer gap? till now I searched a lot of group, all of them can do at least 3 mil=76 micrometer gap. But for my research I need to fabricate a copper gap of about 25 micrometer.
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You can contact Coherent Labs since you are based in USA.
FOR IMMEDIATE ASSISTANCE, PLEASE CALL +1 734 456 3100 - the contact detail of Coherent Labs.
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Lets say we have a substrate without any background noise which is coated plasmonic nanomaterials (Au or Ag N.P) just like the schematic image below. Since In Raman measurements 3 lasers with different wavelengths (532nm/633nm/780nm) can be used, based on absorption wavelength of both organic analyte and plasmonic nanoparticles, Does absorption of Light by N.P can contribute to the SERS enhancement? which of the following conditions is ideal for SERS measurement and can give us better peak enhancement ?
Condition 1: wavelength of laser should be close to absorption wavelength of Analyte
Condition 2: wavelength of laser should be close to absorption wavelength of Plasmonic Nanoparticles
Condition 3: it is better that both analyte and N.P have similar absorption wavelength
Condition 4: There is no overlap of absorption wavelength of analyte and N.P
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Be careful to know the photophysical properties of your "organic analyte" well. Fluorescence is a far more probable process than the stokes Raman scattering for many organic molecules and it will potentially drown out any meaningful SERS data.
Higher wavelength lasers (785 nm) are often chosen for SERS for this reason, particularly avoiding being on resonance with the analyte of interest.
Ultimately it depends entirely on the analyte you are interested in, but you should be able to get good SERS data from simply choosing a wavelength that has resonance with your plasmonic material and not your analyte at all.
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i am trying to learn laser locking in Rb87 saturation absorption spectroscopy setup, while reading few papers i cam across the term "subnatural linewidth", I understand linewidth to be the FWHM of a spectrum output, what does subnatural means?
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so for example , CPT resonance is a subnatural linewidth, is it?
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I have a laser beam whose Polarization State Extinction Ratio is 20db.
I need to calculate the fresnal reflections of the beam from each surface of the lens.
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I’m afraid the answer is you can’t. You are going to have to assume some transverse intensity profile to do the integrals at each lens surface.
On the other hand, if the optics aren’t too fast and the angles aren’t too steep, the Fresnel coefficients don‘t change all that rapidly with angle, and even a rough guess at the beam profile will give a pretty good answer.
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I am trying to build Raman spectrometer and selected the components accordingly and bulit it as per the layout shown in the attachment.
Every component is checked individually & alligned properly but inspite of all that i am getting strong Rayleigh signal.
I used dichroic mirror & cleanup filter to filter out the rayleigh signal. the filters are from Iridian. the Laser wavelength is 785nm
What can be the issue with this type of configuration
Any suggestion / solution will be extremely helpful
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You probably have to check the OD(optical density) of the dichroic and cleanup filter. Generally it should be high (4 to 6) depending on the sample you are investigating. For biological samples your raman signal is quiet small compared to the plastics e. g. Pmma. Please also make sure that your grating of the spectrometer is positioned to correct wavelength. Moreover a laser cleanup filter might help just after the laser as it would make sure that your laser pulse width is very narrow.
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Hi Dear all,
Hope you are doing well. Can some body suggest or share the best book for the laser beam alignment? I am new at this field, kindly give me some suggestions, thanks a lot.
Regards
Johar Zeb
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Mainly make sure the 3 beams in the sample are focused to the same spot. Mirrors should have adjustments to make this happen. OPA/OPG and SHG/THG need to be combined and colinear. Again mirror and optics holders should have adjustments. Depending on frequencies you may need materials to make the laser beams visible (usuallth there are cards with fluorescent or phosphorecent materials that show a visible spot.) There will be issues with pulse timing that are not part of alignment.
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Hello All. I know how to calculate energy fluence (W/cm^2) of a pulsed laser, but if I shift the laser beam at a certain speed (cm/s) along a route I guess energy fluence will decrese. How scanning speed affects the energy fluence into a fixed point, is there a formula available? Thank you!
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How to calculate laser scan speed?
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During AFM imaging, the tip does the raster scanning in xy-axes and deflects in z-axis due to the topographical changes on the surface being imaged. The height adjustments made by the piezo at every point on the surface during the scanning is recorded to reconstruct a 3D topographical image. How does the laser beam remain on the tip while the tip moves all over the surface? Isn't the optics static inside the scanner that is responsible for directing the laser beam onto the cantilever or does it move in sync with the tip? How is it that only the z-signal is affected due to the topography but the xy-signal of the QPD not affected by the movement of the tip?
or in other words, why is the QPD signal affected only due to the bending and twisting of the cantilever and not due to its translation?
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Indeed, in the case of a tip-scanning AFM the incident laser beam should follow the tip scanning motion, to record throughout the deflection signal for the same spot on the cantilever backside. This can be achieved by integrating the laser diode with a kind of tube (with its long axis parallel to the z-axis) that carries the cantilever holder at its lower end and is kind of hinged at its upper end. The scan piezos would act on the entire tube, incl the laser diode, in a plane between the tube's upper and lower ends. Whether or not your AFM system works exactly the same way I cannot tell for sure though.
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I am looking to purchase a Laser micromachining system for fabricating microfluidics devices with 35micron rounded channels from PDMS, PMMA or glass. What is the best make and model to achieve this type of feature resolution and what system parameters are the most important ones that I should be aware of? Thank you
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Standard CO2 lasers are cheap but not easy to use to produce round channel with precises dimention. Femto laser like one from https://www.femtoprint.ch/ can be use to produce channels into a specific glass material with a two step etching: 1. laser pre-condition glass and 2. channels are wet etched https://www.degruyter.com/document/doi/10.1515/nanoph-2017-0097/html
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I'm trying to set up an optical system that can generate a circularly polarized light to excite my specimen. My question is how to guarantee or test that the circularly polarized state is still preserved after the laser pass through the objective lens? I'm sure the polarization is still good before entering the objective lens, but it seems a little wired after the laser pass through the objective lens.
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Hello,
It mainly depends on if you are overfilling the objective lens or not. If you are overfilling the object the actual lcp or rcp polarization distribution of the beam will be get tighter. To make the change of polarization distribution less prominent, your beam size before the lens should be quite smaller compared to the back aperture size of the objective.
I hope this helps.
Thanks
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Cold plasma is characterized by a thermal non-equilibrium between heavy particles (ions, meta stables, neutrals) and light particles (electrons),and is characterized by a low current discharge under atmospheric conditions, generated by application of high voltages.While the most common laser output characteristics include: wavelength, gain bandwidth, monochromatic, spatial and temporal profiles, collimation, output power, coherence and polarization.
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Dear Virendra Nath Rai
Thanks you
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Mach Zender intensity modulator which could modulate the continuous laser source.
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Mohit Mitta The amplitude of an optical wave is controlled via a Mach-Zehnder modulator. The input waveguide is divided into two interferometer arms. When a voltage is put across one of the arms, the wave traveling through that arm experiences a phase change.
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I know the question is quite stupid since basic MOPA need isolator to prevent backward reflection and reduced noise. But there are no isolator in our lab thus we just operate MOPA setup without cladding mode stripper (CMS) and isolator. The amplifier setup is bidirectional pump.
To operate the MOPA seed laser is set to 5W and the pump power at the amplifier increase. When the pump power is low the output power of the whole MOPA setup is increase. But suddenly at one point a sudden drop occur (5W to 1W) and the ouput power insignifacntly increase by increasing pump power. When the power drop high output power was recorded at the end of FBG at the signal port. Based on previous experience at the end of high reflector (HR) FBG, its power should be low (mW in my previous case) but for this setup it output recorded around 2W.
there are 2 possibilities for this issue either the HR FBG is not good enough or due to the MOPA setup that no equoped with CMS and isolator
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Lasers are well known for their coherency. I was wondering to ask whether it is possible to make white light coherent? Of course, a long coherency length the same as lasers is not intended/expected but a coherence length of 10-30 cm.
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Arman Arefi a coherent, continous white light beam is pretty much a self-contradicting statement.
If light is coherent and white, it comes in pulses.
If light is coherent, but does not come in pulses, it is not white.
If light is white and does not come in pulses, it is not coherent.
Pick one.
Note that femtosecond lasers can often have high repetition rates - 70-80MHz, or in special cases even multi-GHz. For some applications, a source with this high repetition rate may work as a quasi-continous source. For others, of course, this may not be the case.
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Hi. I have a question. Do substances(for example Fe or Benzene ) in trace amounts (for example micrograms per liter) cause light refraction? and if they do, is this refraction large enough to be detected? and also if they do, is this refraction unique for each substance?
I also need to know if we have a solution with different substances, can refraction help us determine what the substances are? can it measure the concentration?
Thanks for your help
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It is also on ResearchGate. Author Shangli Pu. Measurement of refractive index of magnetic fluid by Retro - reflection on fiber optics end face.
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In a bounding Nd:Ce:YAG/Cr:YAG rod, two different profiles were recorded on the sensitive photographic paper. one of these profiles has a high divergence while by rotating the rod around the Y-axis, the profile changes completely.
It should be noted that there is no mechanical pressure on the rod.
A sample of the recorded profile is attached.
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If the rod was rotated in an oscillator, perhaps the beam mode would be changed.
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HI,
I am looking for supplier who can provide High power DFB laser. 1540nm and 1570nm +/-3 nm
If low wavelength is 1539nm then upper one should be 1569 (spread is 30nm).
The output power should be min 50 mw and linewidth 1mhz and less. other company like labresource have low output power.
But their lead time is insance 17 weeks.
Any suggestion ?
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Mahmoud,
Hi. Did you check the suppliers in the following link?
Moreover, you may check if you can find something close to your needs in the following link
I hope you find the links helpful.
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A LP free-space Laser source's MFD, waist and other factors (e.g. z, x-y and rotation offsets) get well aligned with a PM fiber coupler (slow axis is in vertical). How and why will the PM fiber coupling ratio (%) be varying with the different polarization incidence angles, e.g. Vertical, Horizontal and Diagonal?
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as far as I know in fiber optics
mode excitation in fiber depends on the entrance angle and this might affect coupling ration
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As being an amateur Quantum Optics researcher, I am looking for RG's help with comprehend a few questions re. my fiber Labs.
1. Assuming HeNe laser sources with LP and Random polarizations (RP), let such lights pass through aligned-fringe pattern interferometer (I had only done LP laser). Is there any difference in the TWO sources' output interference patterns? Why?
2. A LP free-space Laser source's MFD and waist get well aligned with a PM fiber coupler (slow axis is in vertical). How and why will the PM fiber coupling ratio (%) be varying with the different polarization incidence angles, e.g. Vertical, Horizontal and Diagonal?
What will be their output characteristics at the PM fiber output end in terms of polarization states?
3. To control a SM fiber output polarization, it can be done by using a fiber-stress type polarization controller. How if I can or cannot control a PM fiber output polarizations by using such controller?
4. How if a typical ED (Erbium-doped) fiber can be used as a CPA (coherent perfect absorber) for certain absorption Laser frequencies?
Or, if one can devise a ED fiber being the exact opposite of the laser process. In turn, make a design what we term a CPA. The ED fiber device perfectly absorbs incoming coherent laser light with given frequency and turns it into some form of internal energy — EM heat or energy.
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The incandescent light source is not considered a coherent source.
This source has a very short coherence time, and you cannot consider it a thermal light though.
another how it could HeNe laser and randomly polarized at the same time!
honestly, I cannot see how could please explain how it is a laser system and randomly polarized.
if you are going to use a thermal light the fringes will be washed-out.
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Hi, I have a pulsed wave Nd: YAG laser equipment with a maximum single pulse energy of 90J and a maximum peak power of 6kW, and the parameters that I could change are current intensity (A), pulse width (ms), and frequency (Hz). I would like to know how to calculate the energy per pulse for these three parameters (e.g: current intensity - 50 Amps, pulse width - 1.0ms, and frequency - 20 Hz)?
Thank you in advance!
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Perhaps an energy meter or power meter is needed
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Hello,
I want to take the Temperature and Humidity from DHT11 and send this data with KY-008 to Photoresistor.
I have two Arduinos,one of them will transmitter and other one will receiver.
So i can send pre-defined text like "United States" but i am a bit confused about how to send live data through this system.
System diagram just like the attached SS.
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DHT11 provide analog output, where as the Laser diode need digital output. if only ON/ OFF is the purpose then use below code, include dht.h header only. for other way around if you want to send whole analog data of the DHT11 to one Arduino to another used esp8255 much better results. in fact DHT11 can directly connect to ESP8255.
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Hello,
NB : Attachment
Why do i get a different water peak when i compare a 532 nm wavelength (green laser) to 633 nm wavelenght (red laser). Why the band is not here when i'm using the red laser. For this experiment, i'm just switching the laser source and the filter. I'm not moving the sample.
My sample is a substrat of Re with gold nanopaticles in a perchloric acid solution.
Thank you for help !
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Well, the first obvious answer would be that it isn’t a Raman line. Converting your 532 data to absolute wavelength that peak appears to start at 633 nm and extends to about 665 nm. So ask yourself how you could be getting those wavelengths into your experiment.
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I tried to build up a Raman system.
But always can't work in 671/785/830 nm. I always detect laser light.
532 nm can work in same system.
I check laser almost 0o excitation and edge filter 0o pass.
Moreover, this phenomenon would improve when I measure rough surface sample or 45o excitation.
I suspect is Laser class problem, but do not know how to verify.
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You need to describe better your system.
It is usual to have a "clean up" narrow band interference filter on the laser to clean it up first. The laser is then usually directed to the sample by an edge, or notch filter, the spectrum of which is angle dependent, and so how clean the cut off of the laser on the Stokes edge depends on the quality of the filter and the angle.
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I did some measurements with Polytec laser vibrometer instruments to obtain the natural frequencies and mode shapes of the different beams I have in the laboratory.
After doing modal analysis, the mode shapes are not smooth although we did with a dense number of measurement points (we did the measurement in 2D and 1D and for both the mode shapes are not smooth). The material of the beam is concrete.
Who has the same experience?
I look forward to hearing your suggestion.
I can not repeat the tests and I may do smoothing. But all papers that used this instrument had the initial mode shapes, smooth.
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Dear Fahime, I am a colleague of Alexander from Polytec, I am working in the applications department. In order to support you, I would have some questions myself (sorry...):
- if you look at the measured deflection shapes in the PSV software itself: do they look smooth there and is the distorted shape only appearing when you do modal extraction (so curve fit) with an external software? Or is it already distorted within PSV?
- in case it is already distorted within PSV, could you try to animate just slightly next to resonance peaks to see if it looks ok there?
- easiest and most direct would be: could you upload the measurement data somewhere so that I can have a brief look at them?
Best regards,
Jochen
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This idea may be a bit whimsical, and by reviewing the information I only learned that lasers can cool atoms. I was wondering if there are lasers or other techniques to achieve line range cooling of materials, like pre-treatment before laser cutting. Achieving material cooling means that the energy absorbed by the object should be less than the energy radiated by the electromagnetic waves, so I welcome any whimsical discussions!
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Ibrahim Abdelhalim I'm sorry for replying you so late. Actually, I don't do related research. I just thought of the laser sword in the sci-fi movie when I saw the reference of laser heating. Is it possible to use laser to cool macroscopic objects? ? In the comments, a scholar recommended some references related to cooling atoms, I don't know if it is the type you are interested in. I figured it would be helpful if lasers could achieve laser-irradiated skin cooling, but it's just a wild idea at the moment
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In the method I know the water colected at the end of the plots must be dried and then wheighted for us to obtain the mass.
Is there a route in wich we don't need to dry the samples?
I am aware of LASER, topic/surface and other approaches applied in erosion plot scales, but I'm interested in keep using the samples of water + soil.
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You might get a few ideas from a couple of our papers, Hazel Pistol Erosion Plots and Sediment from a Small Gully (not exact titles) in Researchgate. One must find suitable way to separate sediment from the typically large amount of water. Filtration is one approach, separating coarse sand and larger particles from the fine sediments and taking samples of the suspended mix and filtering and drying is another.
If the samples are taken during the storm hydrograph, such as grab samples, or proportional samples taken when wading the cross section, it can be difficult to get appropriate sampling in fast changing conditions. The filter fabric fences in the small gully article, filters the sediment +water mix, leaving the sediment to be volumetrically sampled, dried and weighed.
For fine sediment concentrations, you might be able to calibrate sample measurements of filtered and dried samples with preprocessed turbidimeter readings. Turbidimeters would not capture particles that settle quickly, and some refraction of light interference from organic particles, etc. If no access to ovens to dry samples in remote field studies, you might try constructing solar oven, or developing procedure of calibrating wet weights of filtered samples with dry weights.
There are all sorts of potential error in this type work. Recognizing this, it’s best to stick with standard approaches, or at least do some cross checking between standard and method adjustments used, and those variants fully described.
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I want to model laser melting of a solid block in Fluent with VOF using inert gas and metal substrate domains and solidification/melting. I am new to writing UDFs and have written UDF for energy source term including laser source, convection and radiation from the gas-metal interface. The UDF compiles without any error but Fluent crashes on running with SIGSEGV error. I have attached my domain in the image.
I request you all to please give some guidance as to how to design the problem? Here is my UDF:
#include "udf.h"
#include "sg_mphase.h"
#include "mem.h"
#include "sg_mem.h"
#include "math.h"
#include "flow.h"
#include "unsteady.h"
#include "metric.h"
#define A 0.4 // Absorption coefficient
#define P 200 // Laser power
#define R 80e-6 // spot radius
#define v 0.1 // scan speed of laser
#define h 25 // Heat transfer coefficient
#define Ta 298 // Ambient air temperature
#define s 5.67e-8 // Stefan Boltzmann constant
#define e 0.5 // Emmisivity
#define Pi 3.1415926535
#define Ts 1658 // Solidus temperature
#define Tl 1723 // Liquidus temperature
#define x0 -100e-6 // Initial x position of the laser
#define y0 0.0 // Intiial y position of the laser
#define Lv 7.45e6 // Latent heat of Vaporisation
#define Tv 3090 // Evaporation Temperature
#define Rg 8.314 // Universal Gas constant
#define M 0.005593 // Molar mass
#define Pa 101325 // Atmospheric pressure
#define domain_ID 3 // Domain ID of metal substrate
DEFINE_ADJUST(adjust_gradient, domain)
{
Thread *t;
Thread **pt;
cell_t c;
int phase_domain_index = 1.0;
Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,phase_domain_index);
{
Alloc_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NULL);
Scalar_Reconstruction(pDomain, SV_VOF,-1,SV_VOF_RG,NULL);
Scalar_Derivatives(pDomain,SV_VOF,-1,SV_VOF_G,SV_VOF_RG, Vof_Deriv_Accumulate);
}
mp_thread_loop_c(t,domain,pt)
if (FLUID_THREAD_P(t))
{
Thread *ppt = pt[phase_domain_index];
begin_c_loop (c,t)
{
C_UDMI(c,t,0) = C_VOF_G(c,ppt)[0];
C_UDMI(c,t,1) = C_VOF_G(c,ppt)[1];
C_UDMI(c,t,2) = C_VOF_G(c,ppt)[2];
C_UDMI(c,t,3) = sqrt(C_UDMI(c,t,0)*C_UDMI(c,t,0) + C_UDMI(c,t,1)*C_UDMI(c,t,1) + C_UDMI(c,t,2)*C_UDMI(c,t,2));
}
end_c_loop (c,t)
}
Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NULL);
}
DEFINE_SOURCE(heat_source, c, t, dS, eqn) // The name of the UDF is heat_source
{
Thread *pri_th;
Thread *sec_th;
real source;
real x[ND_ND], time; // Define face centroid vector, time
time = RP_Get_Real("flow-time"); // Acquire time from Fluent solver
C_CENTROID(x, c, t); // Acquire the cell centroid location
real T = C_T(c,t);
real alpha = C_VOF(c,t); // cell volume fraction
real gamma = C_LIQF(c,t); // cell liquid fraction
real Pv = 0.54*Pa*exp((Lv*M*(T-Tv))/(Rg*T*Tv));
real mv = (0.82*M*Pv)/(sqrt(2*Pi*M*Rg*T));
real rhog = 1.6228; // density of argon
real rhos = 7900; // density of solid SS316
real rhol = 7433 + 0.0393*T - 0.00018*pow(T,2); // density of liquid SS316
real rhom = rhol*gamma + rhos*(1-gamma); // density of SS316
real rho = alpha*rhom + rhog*(1-alpha); // density of cell containing metal and gas
real Cpg = 520.64; // specific heat of argon
real Cps = 462 + 0.134*T; // specific heat of solid SS316
real Cpl = 775; // specific heat of liquid SS316
real Cpm = Cpl*gamma + Cps*(1-gamma); // specific heat of SS316
real Cp = alpha*Cpm + Cpg*(1-alpha); // specific heat of cell containing metal and gas
real factor = (2*rho*Cp)/(rhom*Cpm + rhog*Cpg);
pri_th = THREAD_SUB_THREAD(t, 0);
sec_th = THREAD_SUB_THREAD(t, 1);
if(C_VOF(c,sec_th)>0.05 && C_VOF(c,sec_th)<1)
{
if(C_T(c,sec_th) < 3090)
{
source = (((2*A*P)/(Pi*R*R))*exp((-2*(pow(x[0]-x0-v*time,2.0) + pow(x[1]-y0,2.0)))/(R*R)) - h*(T-Ta) - s*e*(pow(T,4) - pow(Ta,4)))*C_UDMI(c,t,3)*factor;
dS[eqn] = 0.0;
}
else if(C_T(c,sec_th) >= 3090)
{
source = (((2*A*P)/(Pi*R*R))*exp((-2*(pow(x[0]-x0-v*time,2.0) + pow(x[1]-y0,2.0)))/(R*R)) - h*(T-Ta) - s*e*(pow(T,4) - pow(Ta,4)) - Lv*mv)*C_UDMI(c,t,3)*factor;
dS[eqn] = 0.0;
}
}
else
{
source = 0.0;
dS[eqn] = 0.0;
}
return source;
}
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Hi, Pawan Dubey
I benefit from your code a lot. Really appreciate your sharing.
SIGSEGV error usually occurs when the udf uses an empty macro. In case anyone is interested in using the code, the error is in:
real alpha = C_VOF(c,t); // cell volume fraction
real gamma = C_LIQF(c,t); // cell liquid fraction
In VOF the main tread points to the mixture phase, thus C_VOF(c,t) and C_LIQF(c,t) are empty. So in order to get VOF and LIQF information, the code should be:
real alpha = C_VOF(c,tsub); // cell volume fraction
real gamma = C_LIQF(c,tsub); // cell liquid fraction
Here tsub is the sub-thread of the metal phase, which is pri_th or sec_th in the code.
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I am stretching ultrashort laser pulses by passing them through an SF11 plate. The pulses are stretched due to the introduction of different delays to the group velocities of the various frequency components. Does this process also produce new frequency components (on the red and blue ends of the spectrum) in the pulse?
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Raul Rangel-Rojo sir, thank you for the suggestion. We are using an amplifier to obtain intense ultrashort pulses, so it might lead to SPM after the pulse passes through the medium. I shall calculate the dispersion length.
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laser 3d printer
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The curing wavelength will depend on the used photoinitiator. Most photoinitiators have effective absorption on the UV length. On the other hand, some photoinitiators such as Camphorquinone have a considerable absorption up to 465 nm and may be used to cure in the visible light.
More information about the longest absorbed wavelength (nm) can be find at
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Visible to UV Up-conversion luminescence for inorganic phosphors can be achieved only when Laser is used as excitation source but if we want some practical application, Vis to UV up-conversion should be obtained by Xenon discharge lamp excitation. So is there any way to achieve Visible to UV Up-conversion luminescence without using Laser as excitation source?
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Dear Sumedha Tamboli,
Firstly let's pay attention to term "up-conversion luminescence" - next be UCL. Wikipedia doesn't know this tag UCL. I can suppose You mean luminescence that can be registered at two photon absorption at very intensive radiation by an adequate type of laser. The same result about luminescence You know can reach with UV emission of xenon, mercury and X-rays source also. Registered spectra should be the same. But most simple method, to my mind, to apply for your work UV-, or near UV diode lasers. Have a nice day!
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I am interested in understanding how heavy particle temperature and electron temperature are experimentally measured in nanosecond laser-generated plasmas during the discharge phase (i.e., when the laser is still on). In particular, I would like to know if the measures are line-average (or volume-average), or if it is possible to map the full 3D temperature fields as a function of time. Thanks.
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Hello, Andrea
You cannot measure the temperature using OES during the breakdown event because it relies on the Boltzman LTE assumption which is not necessarily true.
A better method for measuring temperature (electron, vibrational, rotational, translational) would be through laser scattering methods: Thomson scattering for Te, Raman scattering for (Tv and Tr) and Rayleigh scattering for T. This is not an easy measurement to perform but I'm hoping to measure Tv and Tr during breakdown over the next few months to at least be able to tell you how far/close we are to thermal/equilibrium plasma during breakdown.
I don't know if this helps too much. Unfortunately we are still lacking detailed measurements during the breakdown phase.
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I´m using a protocol in order to detect by flow cytometry (using a 488-nm laser and 530-nm/30 filter or similar) whether my cells are positive for B-galactosidase or not. In this protocol I have to fix the cells with paraformaldehyde to 2% in PBS during 10 minutes before incubating with the working solution. After detecting my cells positive and negative for B-galactosidase I have sorted these two populations of cells and I have performed a cell cycle analysis with propidium iodide (IP). As these cells were fixed with 2% paraformaldehyde, I have had to adapt the recommended protocol for the cell cycle analysis (fix with 70% ethanol and incubate with RNAase + IP) and instead of fixing with ethanol I have permeabilised my fixed cells with 0,25% triton x-100 during 15 minutes before incubating with IP. The problem is that when I have analysed the phases of the cell cycle, they are not distinguished as good as with the recommended protocol. I have also tried to look for the cell cycle with 7AAD but the results were even worst. Does anyone know how can I adapt my protocol in order to improve the cell cycle analysis in the cells already fixed with paraformaldehyde?
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It will be the fixation that is causing DNA damage. Use fresh 1% PFA made from prilled solid stock (signa-aldridge 441244) in PBS with the pH carefully adjusted to 7.4. If using suspension cells 10 min fixation with three washes of PBS. You can then treat with triton X100 etc. as above.
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I was reading a paper introducing the Delayed Self-Heterodyne Interferometry technique by Okoshi in 1980. It was aimed to measure the linewidth of lasers and the main set-up was something like a Mach-Zehnder interferometer, but one of the arms was delayed by a fiber path much longer than the laser's coherence length, and there was an AOM in the other arm [I don't know if it's important]. The interference of these two beams was claimed to indicate the linewidth of the laser. What I do not understand is that how these uncorrelated beams do interfere?
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For the coherence time the laser’s frequency and phase are stable(ish). Interfering two snippets of the laser from different times, they may have different frequency and phase, but for a coherence time the frequency and phase of each is well defined and they will interfere producing a beat frequency. After a coherence time their phases or frequencies will have drifted enough that the beat frequency and phase drift. However, if the coherence time is longer than your detector bandwidth, you have already recorded the beats that happened during that coherence time. The beat frequency and phase will drift through all possible relations presented by the bandwidth of the laser, but it will all be recorded in the time record.
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I used beam profiler like the camera-based Cinogy beam profiler and the BP209 beam profiler from Thorlab to measure the beam profile of laser output from DFB laser’s output fiber directly. The beam profile is a perfect Gaussian shape. And then I used an industrial CCD camera to replace the original beam profiler. The beam profile is kind of different. It has some stripes which doesn’t changed much even I adjust the position and layout of the output fiber and cut the fiber over and over again. It looks like some kind of interference but I don’t know exactly how it occurs and why it only visible to the industrial CCD camera, not the professional beam profiler. Anyone can explain it? The attached files are the beam profilea captured by the CCD camera and the spectrum of the DFB laser.
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Let me add:
- Some CCD cameras have an optical window on the sensor chip, while others have not. Beam profilers often have no windows to avoid such interference problems with coherent (laser) radiation. Best check your case(s) with the data sheets of the sensor chips/manufacturers.
- Other sources of interference stripes may be planeparallel optical elements such as optical filters, etc.
- In order to find the origin, you may slightly touch each optical element in the beam path while monitoring the beam profile and carefully observe the impact on it.
- Generally: parallel interference stripes are often caused by interference from "planeparallel" interfaces, while circular ring patterns may arise from damage or maybe just particles on an optical element only. However, for developing a ring pattern, some subsequent beam propagation distance is required. So dust particles directly sitting on the sensor chip do not cause such ring patterns and will not leave their pixel position when touching other optical elements..
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I wan to simulate a broad area laser diode on Zemax and I was wondering what value should AI put for the astigmatism. the laser data sheet does not provide a value for the astigmatism but instead it tells me the parallel and perpendicular divergence. Is there an equation to calculate the astigmatism of a laser diode through the parallel and perpendicular divergence angles?
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Astigmatism the beam parameters are not the same thing. While wavefront errors affect the divergence, so does diffraction which depends on the intensity profile. Also, astigmatism is not the only wavefront error that affects divergence. So, in short, they are not directly relatable.
Now, generally the wavefront at the output facet of a laser diode is pretty much flat. There are ways this doesn’t have to be true, but in practice it almost always is. It’s a plane wave. There is no astigmatism. There is no focal power. There aren‘t any of the other Seidel aberrations.
When that is the case, the divergence is determined by diffraction, and diffraction is determined by the transverse mode. Edge emitting diodes tend to be single mode in the thin dimension and multimode in the fat dimension. The divergence in the thin dimension is close to the best possible diffraction limited divergence, but because the nearly Gaussian beam is only on the order of 1 micron across, that still produces a large (20 -30 degree half width) divergence. In the fat dimension the beam might be 150 microns and the diffraction limit would allow divergence less than a degree. However because it is multimodal in that dimension it is usually more like 10 degrees. (M^2 >> 1)
The situation is similar in larger mode area lasers such as VCSELs. There may be a size above which thermal curvature of the facet results in significant low order wavefront terms, but you won’t be far off starting with the idea the wavefront is flat.
In Zemax use “Source Diode” to emulate the behavior of your diode. This let’s you describe the diffractive behavior and then defines the source rays accordingly so the proper behavior appears in the geometric ray tracing.
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In LIBS spectra, how lines having self absorption can be indentified and how self absorption can be removed?
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Hi we want to see the laser pulses(femtosecond pharos, 1030nm, 100KHz, 180 fs) with oscilloscope, what should be the settings we need to play with to see the signal from the photo diode detecting the laser pulses. we try to change the vertical and horizontal divisions(50 mV and 2 ns) this is what we got we got.
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Hi Melika,
Make sure your PD has higher bandwidth than your laser repetition rate.
secondly, also make sure PD didn't run out of battery. After making sure all of these points, you can auto-reset the Oscope setting and give you the expected signal.
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For comparison purposes, I wanted to get a list of all the currently-available experimental techniques that can be used to probe physical systems that have all the following characteristics:
1. Probes gas phase molecules, either chiral (e.g. epoxypropane) or achiral
2. Can induce ultrafast electron density rearrangement (i.e. on timescales where atomic nuclei are effectively motionless) using linearly- or circularly-polarized laser pulses to induce excited states.
3. Yields results interpretable in 'real-space' as opposed to reciprocal or momentum space
4. Allows for selective orientation of probed molecules
Can anyone knowledgable in experimental techniques make suggestions?
Thanks in advance!
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Hi Steven,
I suggest you look into the second-order nonlinear spectroscopic technique(s) as it checks out for most of your requirements.
Textbooks from R. Boyd and Y. R. Shen on Nonlinear Optics are some good places to start.
Let me know if you have any questions :)
Best,
Faizan.
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we don't have a UV photolithography system. But we have a 405nm direct laser writer But we are not able to pattern SU8 of thickness 20 microns, even by using multiple exposures. Is there any way to do this pattern by using a laser writer?
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For lesser thickness we can use laser 405nm with 100percent filter. If you want to try for higher thickness ,you need to give multiple doses at same point. This will take huge time to pattern complete design.
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Effects laser irradiation on the growth of Candida spp, what method used and mechanism of action
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Visit kindly the following useful RG link:
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I tried to measure PL (with 532 nm laser, power: 2mW, 700V) for CsSnBr3 thin film(500nm) which is 1.8 eV of band gap ( wavelength:690nm).
Unfortunately, I observed double around peak position.
Have anyone seen this kind of phenomenon with PL and how to fixed it?
I think this is caused by CsSnbr3's intrinsic feature but as an PL setup error.
I've never seen this double peak for CsSnBr3 and I got the single peak for PL a couple of years ago.
But, after changing optics setup, this things started to happen .
I also attached PL for cssnbr3 result
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Gerhard Martens Thank you very much for your comment. But I think it is not caused by the saturation artifact of our detector. We set the saturation limit was larger than that intensity. Plus if it's saturated, the peak should be flat not decreased like that.
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Hello all,
I am currently working with Optech ilris 3D instrument, which aquired 3d point cloud data. while operating the instrument, it is unable to calculate the mean distance and even it is not scanning.
On the instrument screen at the Laser option, it is showing "not rdy", and "no to". I have read the manual several times. I could not resolve it. Can anyone help me how to start the laser in the instrument.
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Thank you sir. I have talked with them. They said instrument laser is out of life.
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Hello everyone,
  • So, as he mentioned in his paper that he neglected the Marangoni effect. Up until now, one can control the fluid flow with changing surface tension gradient. But since he neglected this effect, I don't know how I can enhance my fluid flow. I am having exactly the opposite fluid flow that he showed in the paper. (please see the attached screenshot of my simulation). His fluid flow is having curls in the molten pool clockwise but mine is anticlockwise. How else I can affect the fluid flow (Marangoni is out of discussion since he neglected and surface tension coefficient is assumed to be constant)?
  • He also neglected the latent heat in this paper and used recoil pressure to deform the free surface. But in order to apply the saturated vapor pressure in mass flux, latent heat of vaporization is used. You can comment on it too.
I have implemented all the boundary conditions and equations mentioned in the paper. Still, not able to generate the same results. If anyone can help me with it, I would really appreciate it. I am open to discussion as well through chat system or zoom.
paper link:
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as I explained in my previous answers, all these effects are considered, at least in the manuscript you refer to, as volume forces and their magnitude is obtained from empirical expressions. Both phenomena, the recoil pressure, and the vapor-induced shear stress occur due to the same physical effect, namely the rapid evaporation of material. Thereby, the recoil pressure is simply a pressure acting on the keyhole surface and directed in the inward normal direction of the free surface. The shear stress, however, acts in the tangential direction, which can be obtained with/from the normal inward vector.
Best,
Antoni Artinov
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I have profiled a collimated pulsed laser beam (5mm) at different pulse energies by delaying the Q-switch and I found the profile to be approximately gaussian. Now I have placed a negative meniscus lens to diverge the beam and I put a surface when the beam spot size is 7 mm. Should the final beam profile (at the spot size = 7 mm) be still gaussian? Or the negative lens will change the gaussian profile? Is there any way to calculate the intensity profile theoretically, without again doing the beam profiling by methods like Razor blade method? Thanks.
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Gaussian laser beams propagate as gaussian laser beam if their intensity is sufficiently weak so that they do not affect the refractive index of the medium through which they propagate and a linear approximation is valid. Furthermore the
"diameter" of the laser beam should be large compared to the wavelength so that a Fresnel approximation is valid (at least a few micrometers). Also the medium should be (fairly) homogeneous. This is related to the paraxial approximation used (small angles of deflection). The formulas for gaussian beam propagation a easily found in various textbooks. There is no fundamental difference between divergent and convergent lenses. The standard paraxial matrix formulation used in geometrical optics can be used to calculate gaussian beams transformation. The beam is characterized by its "waist diameter Wo" and the position of this waist "xo" with respect to the lens.
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I need a better laser recommendation with low frequency spectrum noise.
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the wavelength range is 40-780nm(visible light)
the output power is 1-10 mW
Continuous output mode
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Recently we ran into a dilemma. We want to characterize our photodetector devices in Si02/Si substrates (prepared by dry transfer). we have two options
1. To get different fiber coupled LASER sources for i-V and i-t characterizations using our probe station with Keithley semiconductor 4200 parameter analyzer.
2. Do free space setup in our LASER lab but we need to buy Keithley SMUs (Free space lasers with optics are available.
Suggestions needed
1. Which setup to go with (please share from your experience)?
2. Can fast i-t responses be recorded with SMU or Semiconductor Parameter analyzer or we must go with the oscilloscope? If we need to go with oscilloscope, then suggestion on how to pick low level currents near noise floor. (need of lock-in amp)
3. If done in Laser lab, we need to buy additional cable connectors and holders for our substrate that needs to be wirebonded (Actually do not know that exact name of those components, would appreciate anyone responding with knowledge about these accessories).
4. Which (2450, 2634B) and how many SMUs do you think we may need if we opt for free space setup.
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I measured the performance of the photodiode using a light emitting diode.
All what I needed is classical laboratory equipment such as pulse generators, sine wave oscillators, power supply oscilloscope and Keithley multimeter.
You can follow the techniques and the set ups in the paper at the link:
Best wishes
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I am using a 550mW green laser (532nm) and I want to measure its intensity after being passed through several lenses and glass windows.
I found a ThorLabs power meter but it is around $1200.
Any cheaper options to measure the intensity of the laser?
(high accuracy is not required)
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Hi, I'm trying to model a gold particle which is shined by a 808nm, 20mW laser. I'm using the RF module - electromagnetic wave, frequency domain to do the simulation. I have set up the wavelength, but don't know how to add the 20mW. I have tried to set a port, but it kept getting mistakes. What can I do?
Thank you very much in advance!
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Dear Yana Li ,
welcome!
The laser beam is simulated a photon stream F whose power is p that can be expressed by the relation:
p = Fx Eph x A,
where F is the photon flux in photons/cm^2/s
Eph is the photon energy Eph=hc/lambda,
h is the Planck constant, c is the speed of light and lambda it wavelength.
and A is the area of the beam.
So you can finally model the beam by F as
F= p lmabda/ A h c in photons/cm^2/s
Best wishes
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Can I utilize laser 0.5W 800nm for view nonlinear process in semiconductors material (TCOS) such as tin oxide thin films?
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You can't make higher order processes dominate at such a low peak power. That is the point of the pulsed vs CW question. So I think it will not be possible.
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I want to know the physics behind the shock waves produced from the surface of solids when laser beam is focused on the surface of solid ?
I want to know as shock waves produced in inside the material is it possible that it produced outside the materia
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You are most welcome dear Giuseppe Pipino
Wish you the best always.
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Please guide me in determining the laser source (specification) needed to for transient photovoltage and photocurrent setup. We have a function generator and oscilloscope. What are other thing required?
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Thank you all for your kind response.
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Could anyone help me with how I can write a Model selection for a dynamical system with delay for laser resonator?
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Ali Saleh Ba Rajjash To summarize, Python is the most popular language for machine learning, AI, and web development, and it supports PGM and optimization well. Matlab, on the other hand, is the obvious victor for engineering applications, with a plethora of useful libraries for numerical analysis and optimization.
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Hi,
I am planning to simulate nanosecond pulsed laser heating/ ablation on metal. Comsol or Lumerical, which would be the best for this simulation? Also, I would appreciate if anyone can suggest me a good tutorial on that. Thanks.
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WHAT VALUE OF SHAPE FUNCTION CAN BE CONSIDERED IN THE GIVEN FORMULA OF LASER ?
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I have learnt so much, thanks to you.
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What is inverse bremsstrahlung phenonmenon in the generation of laser induced plasma?
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One of the best books explaining the mechanism of light absorption through inverse bremsstrahlung is "Physics of Shock Waves and High-Temperature Hydrodynamic Phenomena" by Ya. B. Zel’dovich and Yu. P. Raizer https://www.amazon.com/Physics-Shock-High-Temperature-Hydrodynamic-Phenomena/dp/0486420027
See Chapter V. Absorption and emisson of radiation in gases at high temperatures. Please note that when calculating the absorption coefficient of laser radiation in a plasma through the inverse bremsstrahlung mechanism together with photoionization (the Unzoeld-Kramers formula), it is also necessary to take into account the correction for stimulated emission, which in the case of laser radiation can be significant.
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Dear all,
I am trying to optimize my panels for our confocal laser microscopy experiments and with our available laser/filter setup, it would be great to have antibodies/Streptavidin that would be coupled to a fluorochrome with a more or less narrow excitation around 488nm and a emission wavelength around 605nm or longer. It might be wishful thinking, but does anyone know any fitting (new?) colors that would be useful?
Thanks for your efforts & best wishes,
Urs
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Hi: It's an "old" fluorophore, but you could try DCM - https://omlc.org/spectra/PhotochemCAD/html/038.html - excitation max ~490 and peak emission ~620 nm (in methanol). Because it's a laser dye it is very stable.
This book - https://www.chem.ucla.edu/~craigim/pdfmanuals/catalogs/Lamdachrome-laser-dyes.pdf seems to be out of print now but contains a lot of good information on laser dyes (fluorophores used in tunable dye lasers). You might be able to find another suitable molecule there?
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Is it possible to discriminate chiral molecule using Plane polarized laser excitation in the Raman Spectroscopy? What is the effects of P and S polarization in Raman spectra of the chiral molecule in terms of intensity and frequency.
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Paulo Barbeitas Miranda Thank you very much
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I've used a subroutine to represent a moving heat flux (a moving laser), and I'd like to know the temperature under the laser position. I've defined a laser path, however the diagram only shows the temperature of the nodes along the path at the last increment. However, as the laser passes through each node on the path, I want the highest temperature of that node.
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I agree with George Papazafeiropoulos.
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why do we calculate plasma temperature and electron number density of laser induced plasma while performing Laser induced breakdown spectroscopy?
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I interpret this question as "If the electron temperature is determined from the spectrum in LIBS plasma, why we need the electron density and temperature to interpret the spectra?".
The idea behind the determination of Te is the assumption of equilibrium.
Observing the LIBS spectra we get information from a small energy interval. Assuming equilibrium, Te can be considered the temperature of the system, and, togeterh with ne, allows to fully characterize the plasma, determining quantities that cannot be measured. For example, in the calibration-free LIBS, electron temperature allows to determine the concentration of the ground state of a species and therefore the plasma composition.
However, something else must be taken into account.
1) the measured temperature from the spectra is not the electron temperature but the level temperature. Only the assution of equilibrium lead to the equivalence of the temperatures.
2) the plasma is not homogeneous in space and time. The measured spectra is the space and time integration of the emission (if not resolved) and often collects the emission of many pulses. Therefore the temperature is not the physical temperature. However, because the spectra is more intense for hotter plasma, we can suppose that the temperature approximately get information on the hot part of the plasma. However consider that the temperature of the mean spectrum is not the mean temperature.
3) In some conditions the plasma is in non-equilibrium. In this case, with the help of collisional radiative models, the real conditions of the plasma can be estimated.
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Hello,
I was measuring my sample - cellulose impregnated with polyethyleneimine, on a Raman microscope that has back-illuminated CCD. I used 633 nm excitation laser. In my spectrum, I got wavy fringes (due to interference?), but I don't know what causes them. I thought the etaloning effect was prominent only when using NIR laser, but I got the same results using 633 nm, 532 nm, and 455 nm laser (and not with 780 nm or 785 nm).
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Magdalena Król Thank you for your answer. I appreciate it. I knew that fluorescence can be generated by cellulose, but I've never seen such a wavy fluorescent pattern in Raman spectrum (usually I've seen just one broad band of high intensity). Is the wavy pattern "normal" or is it due to some resonances or interferences (as it seems to be periodically repeated)?
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Why plane polarized laser is best for the Plasmonic material based chiral discrimination using Raman spectroscopy comparing to unpolarized light?
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Anoop Sunny Plasmonic waves combine incident electromagnetic waves and a metal electron gas density oscillation. The electromagnetic wave is transverse oscillation, but with oblique incidence and P (or TM) polarization, there is a longitudinal component that interacts with plasma electrons oscillations. For the electromagnetic wave of S or TE polarization, interacting with electrons density component is absent, so it will not participate in plasmons excitation. If you use for excitation non-polarized light, only its P polarized component will excite plasmons; you will lose half of beam energy.
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Hello everyone
I am doing research on optical probing of laser induced shock waves in laser but i am not finding data on that.I want to know what is the basics Physics behind production of shock waves in air due to laser and how it propogates .Please guide me
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It's due to the fact that the laser energy deposition process takes place very quickly. If the energy is deposited on a time scale that's shorter than the hydrodynamic time scale of the medium (typically defined as the ratio between a characteristic length scale and the speed of sound) the local temperature rises in the fluid as the energy can't be disipated away from that location quickly through collisions.
This is quite typical for a ns-laser: If you take the 2 x rayleigh range of your laser focus and divide it by the speed of sound in air you'll see that the characteristic time is much longer than the pulse length. This leads to a rapid increase in temperaure and a rise in pressure. After the pulse is over, the kernel dissipates all of that excess energy through the propagation of a blast wave as it tries to reach back it's equilibrium state. If you want to avoid the formation of blast waves, you either lengthen the time duration of energy addition or change the characteristics of the medium (you could also just play with these parameters to tailor the blast wave strength).
You might find the following paper on the gas dynamic effects induced by laser blast waves quite useful: https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-28-4-5835&id=427547
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Hello everyone,
I have already applied the Gaussian heat source and the next step is to apply recoil pressure in order to make the Keyhole.
I have read many papers but still not feeling confident to apply the recoil pressure. I would really appreciate If someone can explain the modules that I need to use for recoil pressure and some important settings in COMSOL.
Thank you.
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I am also facing the problem to apply recoil pressure in Comsol multiphysics. I will be thankful if someone helps me. Akash Meena
AL Timimi Zahra
Thank You