Questions related to Optics and Lasers
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
I want to understand how I may use a Cyclic Shearing Interfermeter to measure Spatial coherence.My objective is to measure the Coherence function between the interfering beams.Is it possible to use a CCD to measure the intensity of the fringes ?If not,then how to measure the intensity of the brigh fringes of the fringe pattern.
I like to do project in laser measurement system. My objective is to eliminate or reduce the cosine error, abbe error in Laser measurement system. I have Rhenishaw XL80 system.
Please tell the procedure to eliminate that particular error. And help me to complete my project.
Lately, I have received a manuscript containing IR-spectra of a single crystal for optic applications. Authors have shown two IR-spectra (due to copyright statement the figure is schematically attached to the question) at which both materials have 5N purity synthesized through Czochralski method. The blue is the control sample while the orange is their synthesized sample. As it is obvious, the orange curve is deviated from 1000 to 2400 cm-1 and it is not as smooth as blue one. They realized that the difference is due to presence of impurities in their sample, while I think it is not.
Does anyone can help me in this regard? What factor leads to such deviation of not being smooth (from 1000 to 4400 cm-1)? any references related to factors leading to deviation of IR-spectrum of single crystal samples?
Waiting for your respectful answers
I am investigating the dependence of the number of diffraction rings on the concentration in third order non-linear organic dyes (due to nonlinear refraction and nonlinear absorption). Prof. Pramodini  claims that the number of diffraction rings depends linearly on the concentration. However, Prof. Hussain A Badran  assume that the number of rings increases exponentially with respect to the concentration. Our experimental curves on aniline blue and Acid blue 29 showed a linear relationship. However, for Oil Red O, experimental curve is not the straight line and the exponential curve. So, is this relationship linear or exponential?
Thank you and hoping for your insightful response.
1.S. Pramodini, P. Poornesh, Effect of conjugation length on nonlinear optical parameters of anthraquinone dyes investigated using He –Ne laser operating in CW mode, Optics & Laser Technology
2. Badran, Hussain A.; Ali Hassan, Qusay Mohammed; Imran, Abdulameer, A Quantitative Study of the Laser-Induced Ring Pattern and optical limiting From 4-Chloro-3-methoxynitrobenzene solution, Basrah Journal of Agricultural Sciences . 2015, Vol. 41 Issue 2, p51-57. 7p.
I am trying to couple light from Laser with M^2=1, wavelength = 1030nm and beam diameter = 1.3mm. Please suggest a lens for efficient coupling into PCF (say 2um core). As far as I know, I have two options, either to use Aspheric lens or Microscope objective, however, I am not really sure which one would be a best choice. As I understood (Please advice if right or wrong)
For efficient coupling, these points should be considered.
1) N.A of lens should be equal or close to that of fibre (PCF)
2) Lens focus diameter should be equal to core size of the fibre (PCF)
3) Input beam should be parallel to Optical axis (Collimated)
Introducing myself, i am Senior Lecturer/Researcher, Deputy Director (Corporate Planning Division) and Editor-in-chief (EDUCATUM Journal of Science, Mathematics and Technology) in Sultan Idris Education University, Malaysia.
Currently, i am working on optical glass, nanoparticles, glass-ceramics and graphene/reduced-graphene oxide to develop new materials for novel fiber optics and laser glass.
I am looking for international collaborations to extend the research on glass materials. The activity of the collaborations are as follows:
1. Exchange knowledge
2. Mutual research collaboration
3. Invited speaker or keynote speaker in international conference on optical glass
4. Research grant opportunity
5. Research article collaboration
6. Student exchange
7. Visiting professor
8. Memorandum of Agreement (MOA) or Memorandum of Understanding (MOU)
I have a question on how peak fluence is calculated. For a Gaussian circular beam, the peak fluence is the total pulse energy divided by πω2/2, where ω is the Gaussian beam radius. Now my question is about a Gaussian elliptical beam with a 10um x 500um beam spot size, is there a way to calculate the peak fluence? Thanks for the inputs!
Using laser-induced breakdown spectroscopy for quantitative analysis, the researcher aims to use linear regression in finding the relationship between signal intensity and the concentration of the substance. So far, laser-induced breakdown spectroscopy is a young but promising method (shown to be effective and quick in qualitative analyses) but on the aspect of quantitative analyses, it is still somewhat semi-quantitative (that is if it's interpreted from the view of a beginner using the device) such that the relationship in between the signal intensity and concentration is found rather than directly looking for a more direct unit such as grams, milligrams, or parts per million.
Using signal intensity as a variable is somewhat difficult especially when an undergraduate interested (but not highly skilled) in the use of Laser induced breakdown spectroscopy tries to interpret data. This is because the signal intensity can be disrupted by many other factors (such as the disruption of the atmosphere of the sample towards the light path as well as the need for uniformity of the sample compositions). For heavy metal analyses (such as cadmium, lead, and chromium), what can be a good calibration curve in order to prevent false results as well as underestimation/overestimation of data? :)
This is for our study on mycoremediation of tropical white-rot fungi on heavy metal contaminated soil sites, and we're very interested and set in the use of LIBS since unlike other spectroscopic methods, it does not need to have sample preparations and other tedious solubilizations of samples; which are methods that can contaminate our samples. :)
Do you know how to measure longitudinal and transverse modes in lasers? I need to know the cutting edge and experimental techniques related to this subject.
Ruby (Al2O3 doped with Cr3+ ions), when exposed to ionizing radiation (for e.g. X-rays), emits luminescence. What is the mechanism that causes this 'Radio-luminescence? Does Cr3+ accept electrons or give up?
Which simulation software can simulate a Diode side-piumped solid state laser Nd:YAG with one or more gain media or amplifier with multipass configuration. Any suggestions for how to use MATLAB simulink to perform this configurations?
I'm trying match the phase between different links(all the links has same devices with same parameters). As i know i have to place an exact same length of the fiber between all the links to perfectly match the phase between all the links. I'm unable perform exact calculations to match the phase to over wide bandwidth(around 10 MHz to 3000 MHz). I''m able to match at lower frequencies by cutting the fiber length approximately. Once i over but even by few mm length im going out of phase with the link. I need to have 6 degree phase difference between each link. Can some one give exact calculations to match the phase over wide band.?
The question is upon the manipulation of micro particles (of size perhaps ranging from several microns to hundred of microns). We may desire to trap or capture a micro particle (dielectric, opaque or organic materials) and control its three-dimensional location in air/ or manipulate the particle to move along a certain 3D trajectory in relatively high speed (perhaps about 0.1m/s to 1m/s) in ambient air.
Is there any possible/ reliable approaches?
I was wondering if using optical vortices (laser beams of orbital angular momentum OAM in the manner of optical tweezers) is feasible? It seems that currently, they were limited in the manipulations of nanoparticles in a 2D plane and could not support 3D spatial moving big particle of high speed in the air?
I was wondering if some other potential morphologies such as photophoretic trapping with optical bottle beams, thermophoresis or other method can work better?
I'm looking for a polymer (or even a type of tape) that can be used with high energy lasers in photoacoustic experiments.
The material must be able to repeatedly be exposed to 500 mJ/cm^2 from a nanosecond (5 nanoseconds) or picosecond laser pulse (8 picoseconds) without burning AND it must have favorable acoustic properties (an acoustic impedance close-ish to water at 1.5 MRayls) AND it must be optically transparent in the range from 400-700 nm.
Is there anything even remotely close to being able to handle these types of energies/powers in a polymer form or would it all have to be glass?
I have an optical setup for cleaning up the laser diode beam, which includes coupling the laser light into a polarization-maintaining single mode FC/APC fiber.
I have a technical question on coupling the laser light into an FC/APC connector. Should I introduce any tilt on the fiber holder for that? Or should the angled end be tilted with 8 degrees from the optical axis by simply pluging the fiber into the holder?
I understand that with tilting I will lose the advantages of reducing the back reflections into the source. However, the proper adjustment of such fiber is not clear to me.
Thank you in advance for your help!
I want to simulate the interaction of laser with composite materials. i need to know the thermo-physical and optical properties and their changes with temperature.
In fact, I'd like an overview of the characteristics of composites and import them in heat transfer model.(The required parameters are :Absorption coefficient , thermal conductivity,Reflectance coefficientوDensity , specific heat capacity)
I am trying to lock laser at half transmission point of scanning fabry perot etalon (SA200 ) using electrical feedback to laser driver current source.How can I achieve it. my experiment consists of a DFB-LD , input to circulator port 1, at port 2 etalon is connected and observing laser reflected spectrum.the transmitted signal from etalon is photodetected and feedback to laser driver current source.
Thanks in advance.
I'm trying to couple an argon laser into an FC terminated single-mode fiber, and then collimate the output using a 1", 30-mm EFL achromatic aspheric lens. However, I keep seeing a diffraction pattern, like an Airy disc or a Bessel beam when the output is projected on a wall some distance away. Here is what I've tried:
1. Coiling the fiber to eliminate cladding modes.
2. Cleaning both ends of the fiber.
3. Swapping out for another SMF.
4. Swapping input/output ends of the fiber.
In all cases, the pattern persists. Any suggestions?
I want to make optical measurements (fluorescence) of a liquid sample (fluorophore dissolved in 2-methyltetrahydrofuran) inside of a cryostat. The problem is that when I make my sample (in a cuvette) and introduce it into the cryostat once I put it under vacuum the seal on the cuvette does not always withstand the high vacuum of the cryostat. As a result I will sometimes evaporate my solvent before I freeze it.
I would also like to make measurements above the freezing point of the solvent but at temperature that need me to keep the vacuum running this also leads to solvent evaporation. This changes the concentration of the sample possibly adding additional error to the measurement.
I am currently using a 1 or 2 mm pathlenght cuvette with a Teflon plug that I hole down with Teflon tape but this is not working that well.
Are there any special sample holders for this kind of measurement?
if yes, what are they and where can I get them?
If not, is there anybody with experience using cryostats that can offer me some advice on how to make my measurements?
We know that if we use a single cycle/half cycle pulse to generate high harmonics, we may generate single attosecond pulse giving us a broad spectrum as indicated by the continuum. However, we only get discrete frequency combs by using multicycle pulses. Is it that there occurs some kind of destructive interference between various generated harmonics?
In a Raman set up we need very collinear pulsed nanosecond beams. A colleague with experience recommending using two cylindrical lenses (one for each beam before a combining optic), which we can put into the beam path to focus the light to a line. If these lines are collinear they should appear dim due to the destructive interference (they will not be overlapped in time nor do they need to be). Does anyone have experience with this or recommendations for creating very collinear beams? Is this as simple as my colleague made it sound? What sort of focal lengths do you use? Logistical concerns here?
Our use: We plan to use a combining optic to transmit one pulsed ns beam and reflect another ns beam off this combining optic. We will subsequently align our two beams through two sets of irises (this is pretty typical I believe). The irises may not get sufficiently collinear light or may take many iterations and I would like to know other ways people address this problem.
I am on my way to setup a measurement to estimate thermal lensing in my setup with double pass of a probe beam through the crystal. The only problem is how to interpret the data I will receive. Most of the papers give end-result with little insight on the method. So I would appreciate if someone could recommend me a useful paper/thesis/book which could help to understand it more deeply.
I would like to know the maximum rate of pairs of photons that can be generated by SPDC (and detected) with a continuous wave laser (405 nm). The crystal used is a 1 cm long 10 um period PPKT collinear type II crystal. Any reference where I can find this information will be strongly apreciated.
A colleague of mine was doing some laser diffraction analysis for a waste water. We observed some strange effect which we couldn't explain: an analysis with and without ultrasound showed similar results (it said, that there are too large particles, although there are NO visible ones; the range was 0-350 micron). This cannot be true. We cleaned and checked the device (with a standard) and remeasured the sample which we had before: the one already treated with US. The result seems ok. A repition of an original sample with longer US lead to "too large particles" again.
Now my question is:
Are there any molecules/chemical componentes which influence the analysis and pretend to be large particles? Acids, colour, solvents, ....
Setup (refer attachment): laser, sample, detection of fluporescence at 180 degrees from excitation, cutoff filter, band pass filter, detector, TCSPC hardware board, software control for detector and laser.
I carry out these experiments to find out the lifetimes of Erythrosin, Coumarin 540 and L-Tryptophane.
At my early test, I found out that with or without the laser excitation, my TCSPC system gives the same spectrum (refer attachment). It must be something wrong.
By going through the literature, I found out that these kind of experiments are done at magic angle conditions and without the pileup effect. And we also need to measure the IRF (Instrument Response Function) of the systems.
Do I need to insert a polarizers between sample holder and PMT? How important it is? How to find the right one for my system?
Please refer the attachment. Many thanks!
In your opinion what would be the optimum optical scanner for elliptical scanning trajectories (general elliptical, i.e. from line to circular in different sizes).
Which current solutions would you suggest for compact and fast response scanners (1KHz) other than e.g. classical salvo scanners?
Thank you in advance.
We have a MCP PMT which detects in the wavelength range starting from 950 nm to 1700 nm. I have to use 510 nm picosecond pulsed laser to excite the samples I have which usually have emissions around 1200-1300 nm. How should I take the instrument response function with the 510 nm excitation source? No scattering is detected by the PMT as it is sensitive to the NIR region and I am exciting in the visible region.
I am looking for a exact relation to determine the laser beam radius at focus.
Researcher's saying that "It is really wrong to assume that the cladding index is 1 (ncl=1). The properties of PCFs are exactly different from step-index fibers because of the frequency dependent cladding index".
My question is how to calculate the exact value of cladding refractive index "nclad " when most of the part in cladding is air.
the waveguide is attached
A spatial filter is a device to 'clean up' a laser beam with an irregular intensity profile, and create a smooth Gaussian profile at the output.
It is usually said (e.g. here) that you need a microscope objective and a pinhole for this. The microscope objective creates the Fourier transform of the laser beam at its output. The pinhole acts as a low-pass filter in the Fourier plane of the lens, to remove unwanted high spatial frequency components of the beam.
Why is the microscope objective necessary, instead of any other lens with diffraction-limited performance (e.g. aspheric lenses)? What makes microscope objectives more suitable?
I am looking for an analytical expression describing the time evolution of the spatially averaged density (in practice, the average concentration in particles/m3) of a system of particles hopping with a given frequency on a d=3 lattice where some traps are randomly placed. The idea is that when a particle meets a trap it disappears from the system, so that the average density decreases to zero with some decay law. I expect to find something like a stretched exponential decay and I would like to relate the parameters of this decay curve with the input data of my system (e.g. intial particle density, traps concentration etc.) The lattice can be ordered (say, cubic) or disordered (like in glassy media or polymers) and the traps can have a finite size. As a further complication, the effect of traps saturation can be also taken into account.
I am trying to get decent power out of a fiber I am coupling to my laser (dynamic range: 100mW) but am having a hard time. The fiber is 400um multimode, 0.39 NA and is connected to an SMA adapter threaded to a mount whose angle you can adjust. The fiber post is mounted on a translational stage. I do not have any convex lenses between the fiber and lens at the moment because my spot size is already very, very small. But the power that comes out of my fiber when the laser is set to ~60mW is around 1uW... Any tips?
Hello. I have the following situation.
Laser beam: D=5 mm diameter 1/e2, lambda=1064 nm, CW, TEM00.
Fiber: NA 0.13-0.15, mode field diameter w=5.3-6.7 um
In a technical note from Newport, I found that I should be using a lens with focus f=D*Pi*w/(4*lambda).
I found an aspheric lens with f=20 mm, which is close to what I calculated. I aligned it in front of the laser, with flat side facing the laser. I go zero power despite my attempts to align everything, and the beam diameter in focus was about 500 um.
At the same time, according to the Newport tech note, it should match the mode field diameter!
What lens or objective would you recommend to use?
When optic pulse propagates in a fiber it always experience small environment disturbance of it polarization state. Is any pulse stable polarization that hardly can be destroyed ? If such a state exist, pulse polarization have to develope to that from any other state and be stable.
Does anybody have experience with v-groove array coupling with photodiodes on the chip? I need to couple the laser light from V-grooves to the 30um photodiode. I already tried once using the optical bench to couple the PD and Vgrooves. But the efficiency seems very small (<1%). It seems the reflection from the mirror not matched with the PD size or may be the reflection is not uniform. Does anyone have idea about the on chip coupling? I would be also grateful if you kindly describe the gaussian mode matching.
I would appreciate very much, if somebody can give me a connection, where we can get/order standard sample for testing performance of Laser particle size analyser.
Thank you for your help in advance.
I am looking for high power intracavity optics (lens and polarizer).
Wavelength: 755 nm
Pulse energy density: 1.6 J/cm2
Pulse width: 500 ps
Repetition rate: 100 MHz (during pulse build-up for ~ 2 microseconds)
Since the laser system is q-switched, modelocked and cavity dumped, the damage threshold requirement seems to be significantly higher than general stock optics. I have already damaged stock lenses, and some custom-made brewster thin film polarizer before the laser can reach the target energy.
The beam size has been expanded as much as possible inside the cavity with telescope configuration. Only option seem to be to look for a extremely sturdy optical coating.
Does anybody know any custom coating services that specializes in high damage threshold optics or intracavity optics?
(I've heard that hafnium coating is required for high LIDT but do not know about this in detail...)
If I have a 1000 um optical fiber, is there any near field effect from the tip of the fiber if the fiber tip is not tapered? For example, in near field scanning optical microscopy, the tapered tip allows for a near field effect to interact with a surface for imaging, but is there a field that is measurable even with an untapered tip?
I ablated stainless steel target in Hexane and water by UV laser. When I tested the absorbance of the suspension of nanoparticles in Hexane, I observed positive and negative absorbance, The positive absorbance was in UV, while the negative absorbance was in visible, The negative absorbance was not observed in case of water. Please note that both of pure liquids have zero absorbance in UV-V. Can anyone explain the reason?
How does the factor 2*pulse energy/cross section area comes for the gaussian beam and for top hat it it not present? Is this because of the energy distribution within the beam? Does anyone know the proof for this formula or recommend any book where this is mentioned ?
How to calculate the beam waist of Gaussian beam from its intensity in a crystal? Is there any direct relationship between the beam waist and intensity of a gaussian beam?
In the context of a Joint spectral amplitude of an SPDC effect is it possible to model a cw-laser with a dirac delta function?
I am trying to figure out the lifetime of a LASER expressed in hours when given the number of shots fired.
I was thinking that 1x pulse is equal to one shot.
I want to introduce in the scan head of the microscope two laser lines (different lasers). One is already aligned with the system and I need the other one to follow the same path. The problem is the mirror in between that blocks one of the lasers.
That is why I am trying to find a solution and something that reflects what comes front the front and refracts what comes from behind, could work.
This is the only thing I can think of. Any other ideas are more than welcome.
I'm particulary intersted to learn what is the the maximal average power and/or peak power achieved using second-harmonic generation that result in 100-500 ns pulses, especially @ 515/532 nm.
I have a micro projector using a 860nm laser diode.
There is a focal point in the optical path very close to an optical surface.
We would like to use polycarbonate molded optics with AR coatings.
Is there any data supporting this type of testing? I have only been able to find data for nanosecond pulse 1064 lasers.
I'm looking for intensity data for surface damage, bulk damage, and coating damage in W/cm^2.
I installed a simple system consists of 10Gbps NRZ signal and cw pump laser mixed together across pump coupler co-propagating to a SMF. at the end of the fiber, the pump coupler counter-propagation connected. the Raman pump laser connected to this pump coupler counter-propagation. Raman pumping should enhance the conversion efficiency even with lower pump power.
but I didn't see any effect of the Raman pump on the signal.
the wavelengths were, 1557, 1553, and 1455 nm for the signal, pump, and Raman pump respectively. I think the problem in the pump coupler counter-propagation,
Please could any one can help me to solve this problem?
when we consider a fabry perot resonator
the number of longitudinal modes which can be excited = half width / separation of longitudinal modes
why are we taking half width shouldn't we consider the full width of the gain profile
My work is related to theoretical modeling of a phenomenon in semiconductor lasers and I want to submit it in a reputed journal. Most journals in optics and photonics require experimental work. Can anyone suggest some jounrnal which deals with theoretical modeling?
I am using continuous laser for my experiment and photo detectors to detect the laser light, from the detectors I am getting photon counts only, Now I just want to convert photon counts into Intensity in terms of W/m2.
When two counter-traveling modes produce a standing wave pattern in a semiconductor ring laser, population inversion grating is formed which couples one mode to another, leading in unidirectional operation. How is then bidirectional operation still possible?
I have a femtosecond laser (800nm, 1 kHz, 50 fs, 4 mJ) and want to focus with off axis parabolic mirror to a spot size of less than 10 micron. I can focus but difficult to get good quality of focus. generally I obtain bright tiny yellow (if seen on pink paper) spot at the center after focusing however the periphery has also either the hot spots or some distribution of high intensity component. I mean the beam is not fully concentrated at the center. What is remedy you can suggest to me to achieve my goal. what is the proper shape of focused spot? Thanks in advance and appreciation for any kind of suggestions and comments.
A plane wave (laser beam) with an optical power density 0.5 W/cm2 propagate in vacuum (n = 1). That beam travels into a new medium, optically denser than vacuum (n = 2). Is the optical power density still the same? (time-averaged Poynting vector) or the optical power density is multiply by refractive index of new medium?
I'm looking for the least expensive picosecond laser with the following minimum specifications. Ideally, my upper end in cost would be ~$10,000 so anything around that or less would be nice.
Wavelength: 532 nm or 1064 nm (or both)
Pulse duration: <300 pS (shorter is better)
Energy per pulse: 1-5 mJ (for a 6 mm beam, or less energy with a smaller beam to have the same effective radiant exposure)
Repetition rate: Even 1 Hz would be okay, but ideally 10 Hz or more
Any book or paper explaining key differences in the construction, working and dynamics of semiconductor lasers and gas lasers.
I am focusing a Gaussian beam using a High NA objective (NA=1.3). The laser is linearly polarized. I focus the laser at an oil/water interface and image the back reflected light. The image is attached. The profile is not near what you expect, i.e. asymmetric Gaussian. If I lower the NA of the objective the profile is Gaussian again which is expected. I can trap fine. At this point am not sure what is causing this. I appreciate any help.