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# Applied Optics - Science topic

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Questions related to Applied Optics

Hi there,

I hope you are doing well.

In the lab we have different BBO crystals, however, in the past, they did not mark them so we don't know which crystal is which. I appreciated it if somebody have an idea about how to measure the thickness of BBO crystals.

The second question is, are the BBO crystals sandwiched by two glasses or not? If yes is the measurement become complicated?

Best regards,

Aydin

Hi all,

I am testing UV-vis spectrophotometer for PDMS, using "Hitachi U-3900"

My holder for solid can only get reflectance(%R) data,

Schematic of test is Figure 1,

PDMS is a very high transparent material, but its %R is very high(Figure 2), it is weird.

I think most of the light passing through the PDMS and reflected by the Aluminium oxide,

In such situation, can I convert reflectance(%R) into transmittance(%T)?

Thank you very much.

My source laser is a 20mW 1310nm DFB laser diode pigtailed into single-mode fiber.

The laser light then passes into an inline polarizer with single-mode fiber input/output, then into a 1x2 coupler (all inputs/outputs use PM (polarization maintaining) Panda single mode fiber, except for the fiber from the laser source into the initial polarizer). All fibers are terminated with and connected using SC/APC connectors. See the attached diagram of my setup.

The laser light source appears to have a coherence length of around 9km at 1310nm (see attached calculation worksheet) so it should be possible to observe interference fringes with my setup.

The two output channels from the 1x2 coupler are then passed into a non-polarizing beam splitter (NPBS) cube (50:50 reflection/transmission) and the combined output beam is projected onto a cardboard screen. The image of the NIR light on the screen is observed using a Contour-IR digital camera capable of seeing 1310nm light, and observed on a PC using the software supplied with the camera. In order to capture enough light to see a clear image, the settings of the software controlling the camera need to have sufficient Gain and Exposure (as well as Brightness and Contrast). This causes the frame rate of the video imaging to slow to several second per image frame.

All optical equipment is designed to operate with 1310nm light and the NPBS cube and screen are housed in a closed box with a NIR camera (capable of seeing 1310nm light) aiming at the screen with the combined output light from the NPBS cube.

I have tested (using a polarizing filter) that each of the two beams coming from the 1x2 coupler and into the NPBS cube are horizontally polarized (as is the combined output beam from the NPBS cube), yet I don't see any signs of an interference pattern (fringes) on the screen, no matter what I do.

I have tried adding a divergent lens on the output of the NPBS cube to spread out the beam in case the fringes were too small.

I have a stepper motor control on one of the fiber beam inputs to the NPBS cube such that the horizontal alignment with the other fiber beam can be adjusted in small steps, yet no matter what alignment I set there is never any sign of an interference pattern (fringes) in the observed image.

All I see is a fuzzy blob of light for the beam emerging from the NPBS cube on the screen (see attached screenshot) - not even a hint of an interference pattern...

What am I doing wrong? How critical is the alignment of the two input beams to the NPBS cube? What else could be wrong?

Dear reserches,

A silver halide-containing photochromic glasses exhibiting refractive indices between 1.585-1.610 in response to radiation exposure.

This domain is not remarkable due to my experiments.

Could you give me another suggestion?

Kind regards,

Farhad

Recently, I have been troubing in calculating the Lenticular lens Imaging. I want to find a method to calculate the object is imaged through the lenticular lens

I use Fujikura CT-30 cleaver for PCF cleaving to use for supercontinuum generation. Initially, it seems like working fine as I could get high coupling efficiency (70-80%) in the 3.2um core of PCF. However, after some time (several hours) I notice that coupling efficiency decreases drastically and when I inspect the PCF endface with an IRscope, I could see a bright shine on the PCF end facet, which is maybe an indication that the end face is damaged. Also, I want to mention that the setup is well protected from dust and there is no chance of dusting contaminating the fiber facet.

Please suggest what should be done to get an optimal cleave, shall I use a different cleaver (pls suggest one) or there are other things to consider.

Thanks

Hi,

I would like to understand the link between GRD (ground resolved distance) experimental value and the GSD (ground sample distance) theoretical value. I saw somewhere the following formula used: GRD=2*k*GSD when the factor 2 is to get the value of two-pixel ( cyc/mm ), and k would represent a factor that includes all other influences such as turbulence, aerosol or camera aberration.

When k>1 and if k=1 then we talk about an ideal system.

I would like to know is there a formula to calculate k directly to be able to find the GR? Is there a maximum value of k where one can say that the only influence is the atmosphere and that the camera is limit diffracted?

And is there sources talking of this factor, I have not found any on internet.

Thank you very much

In many papers, researchers mentioned the formula below for the optical path length in corner cube reflector, however they didn’t show any proof. I want to understand how they reached to this formula.

The total optical path length of a ray in corner cube reflector is

OPL=2*n*D*sec(theta)

where n is the refraction index of the glass, D is the height of the corner cube (the distance from the apex to the glass face), and theta is the angle to the normal of the corner cube glass face. By snell's formula the sec(theta)=n/sqrt(n^2-sin^2(theta)).

below is some ref mentioned the formula above without proof.

ref:

1- theorem 7 in "Theory of the Corner-Cube Interferometer", EDsoN R. PECK

2- Eq (7), "Simultaneous Measurement Method and Error Analysis of the Six Degrees-of-Freedom Motion Errors of a Rotary Axis",Chuanchen Bao

3- Eq(1), "Laser heterodyne interferometer for simultaneous measuring displacement and angle based on the Faraday effect”, Enzheng Zhang

In my experiment I have a double cladding fiber spliced on to a reel of SMF-28. The double cladding fiber has total cladding diameter about 2 times more than that of the SMF-28. The source is a SLD, and there is a polarization scrambler after the source which feeds onto one end of the reel of SMF-28. The output power from the 1 km long reel is X mW. But when I splice a half meter length of the specialty fiber to the reel output and measure the power it is 0.9Y mW, where Y is the power output after the polarization scrambler (Y = 3.9X). I am not sure why the power reading suddenly increased.

I am interested in the technique of obtaining high-quality replicas from diffraction gratings, as well as holograms with surface relief. What materials are best used in this process? Also of interest is the method of processing the surface of the grating to reduce adhesion in the process of removing a replica from it.

I have a Jones Matrix of the form : M= [ A + iB C + iD ; U + iV X + iZ]

The input Jones vector is E1 = [ 0 ; 1] , linearly polarized light along Y-axis

So the output is E2 = M*E1 = [ a + ib ; c + id]

Now I want to normalize E2, what is the best way of doing it ?

I am thinking about calculating the magnitudes of each element of E2 and using that for normalizing

Hello;

It is well known that when light reaches an optical element, part of it is lost through absorption, diffusion, and back reflection. In the case of mirrors, this value is well characterized and a realistic estimate would be around 4-5% (or less depending of the material). However, I cannot find similar information on commercial or scientific sites for beam-splitters. For example, in a well-known optical products company, if we enter the raw data the percentage of reflected and transmitted light adds up to more than 100% at some points on the curve! Without a doubt this has to do with the measurement methodology.

In the case of scientific articles, some estimate this absorption to be around 2% assuming that it is a block or sheet of a certain material (ignoring ghost images). However, this does not make sense since it would then be more interesting to use a dichroic beam splitter than a mirror in certain circumstances.

Of course everything will depend on the thickness, material used, AR treatment. However, I cannot find a single example and I am not able to know the order of magnitude. Does anyone know of any reference where a realistic estimate of the useful light that is lost when using a beam splitter of whatever characteristics is made?

Thanks !

I am trying to construct an interferometer where I need to use polarizing and non-polarizing beam splitters. Can anyone suggest how to represent the beam splitter matrix for PBS and NPBS?

It sounds that shorter λ (more energy) makes the wave more powerful to go through a specific thickness of the material, but the weaker wave does it better. How are

*?***the interactions of the wave with the molecules**Talking to Dr. Jörn Schliewe inspired me to raise this illustrated question and how you may call these barriers in the experiment of diffraction? Would you call it n-slits or n-obstacles?

What would be the pulse compression limit for initial pulses from fibre laser with average power 4mw, 4.5ps duration and 0.4nm fwhm bandwidth.After amplification to 450mw and propagating through a length of SMF (different lengths can be chosen 5m,10m etc..and hence different amount of spectral broadening) , I want to understand on choosing optimal length of SMF to achieve maximum pulse compression (pulse compression limit using spectral broadening in SMF). How would the length of SMF affect the subsequent pulse compression stage?

Thanks in advance!

Hi,

I'm a researcher in optimization and a hobbyist photographer, and I'd like to get acquainted with lens design via the use of optimization methods. I found for example the paper "Human-competitive lens system design with evolution strategies" (2007).

Are you aware of more recent techniques to design camera lenses? Are there optimization models or benchmarks available?

Thank you,

Charlie

When simulating light pipes, will the choice of a source (collimated beam vs angular beam) make any difference on the efficiency of the light pipe to channel light from source on one end to the detector on the other end.

I had this question for years. I frequently (like almost always) find optic designs that expand collimated SMF output into larger diameter beams (something like two achromats after a small asphere). It makes sense if a system requires beam diameter reconfiguration occasionally, but this also happens in many clearly finalized optical designs. My question is, why don't people collimate SMF output directly into a bigger diameter beams using larger diameter collimators?

I did some quick qualitative test before using a beam profiler and found no obvious difference. There is also little difference with optical simulation. I understand those larger aspheric lenses are more expensive in general, but definitely not by a lot when they are within 1 inch.

I have the refractive indices (n & k) of a thin film. I can estimate the real part of sub-wavelength structures by considering the shape and void fraction using a simple linear relation. However, I could not find any reference to analytically estimate/calculate the imaginary part of such sub-wavelength structures.

I could find the following but, unfortunately, this is not applicable to my question:

Kar, Meenakshi, Bhullan S. Verma, Amitabha Basu, and Raghunath Bhattacharyya. "Modeling of the refractive index and extinction coefficient of binary composite films."

*Applied optics*40, no. 34 (2001): 6301-6306.Would you please introduce a reliable reference or some that are straight forward?

Thanks, in advance.

Dear colleagues,

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 [1] claims that the number of diffraction rings depends linearly on the concentration. However, Prof. Hussain A Badran [2] 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.

Hi everyone. I want to buy rectangular aperture as the beam stop. However, all the apertures sold in the market are circular. I am curious why there is no other shape.

Could anyone tell me where I can buy rectangular (square) apertures? Or give some suggestions that how to make it? Thanks in advance!

how to spliced different different core size (MFD) fibres ( single mode to graded index multimode). I am trying to splice SMF to GIMF, to fabricate SMF-GIMF-SMF saturable absorber.

Although, I could splice with apparently no power loss (shows 0dB loss). However, splicer shows "Bubble Error", even after several attempts.

note:Please have a look at the photos attached

Thanks

We have LG

^{1}_{0}beam only and we have to get HG(1,0).I am concerned about the energies of EM radiations. Like the visible has an energy in the range of 1eV, UV has an energy of 10 eV. So when we shine the EM on a semiconductor, how does it affect the charge carrier concentration of it.

Dear professors and colleagues,

I am going to to study effect of the two photons absorption in Safranin O. Safranin O is organic material, so I think that the power needed to activate this effect doesn't need to be too high. However, the two photons absorption is a third-order nonlinear optical effect, so it is usually implemented with high-power pulsed lasers. I cannot afford to buy high-power pulsed lasers. So, can I stimulate effect of two photons absorption in safranin O by continuous wave laser (808 nm or 1064 nm)? And how much is the required power of laser? I hope the colleagues who have experience in this experiment share me useful information.

I look forward to hearing from you. Thanks in advance.

Yours sincerely.

Dear Colleagues,

I am investigating methods to determine the photodynamic activity of photosensitizers for photodynamic therapy. One of the methods being used is absorption spectrometry. A work concludes that significant absorption of light was shown to be prerequisite but not sufficient for high photodynamic activity. My point of view is: When a photosensitizer absorbs more radiation at a certain wavelength, it will produce more Ros (Reactive oxygen species), i.e the absorption maximum will correspond to the wavelength active photodynamic effect best. However, this point of view contradicts the viewpoint in above work.
I look forward colleagues to explain this question.

Thanks in advance.

I have three collimated optical beams with 1cm separation between the adjacent one. I want to shift one of the three beam laterally so that it goes closer towards or farther away from the adjacent beam by micrometer accuracy.

The laser beam is first expanded to get a elliptical shape beam using a cylindrical lens. This elliptical shaped beam is then passed through a variable attenuator in order to obtain a change in intensity with time. This attenuated elliptical beam is then incident on a fiber of approximately 0.36 mm width, clamped vertically. I would like to know an effective way of measuring what INTENSITY of the laser beam is actually hitting the sample.

Dear Sirs,

The setup for the dispersion measurement is as follows. Hg lamp, collimator, goniometer with triangular prism. We measure the light dispersion using the prism. To do so we determine the minimal deviation angle of the particular color line and then calculate the refraction coefficient (the wavelengths are known from the standard source). To find the minimal deviation angle we rotate the prism.

In the above setup does anybody know whether the smooth minimum of the deviation angle (as a function of incidence angle) can increase the error of the measurement of the minimal deviation angle? Please correct me if there is a mistake.

Assume that you are living in the time when the Gregorian calendar was introduced by Pope Gregory XIII in October 1582, when

Galileo Galilei was about eighteen years old. However, he was tried by the Inquisition, found "vehemently suspect of heresy", and forced to recant 1632, and then he spent the rest of his life under house arrest.

The most noticeable thing in this matter is that people of those years could realize the rotation and subsequently, they could calculate the rate and the duration of the rotation but what was not clear for them was what is rotating around what. At that time what would be your solution?

Now, if I can take this sad historical event as the fact, then I would ask myself if the integral theorem of Helmholtz and Kirchhoff plays a central role in the derivation of the scalar theory of diffraction along with the concept of the wave-particle duality, or it obtains the propagation of light in the diffracted space with an inhomogeneous refractive index?

I am trying to get output of laser beam from a FOC laser beam with diameter ranging from 100 microns to 1000 microns. The FOC diameter is 200 micron and NA is 0.22. What kind of lens or combination of lenses is possible to do this kind of focussing and how much should be the focal size of the lens. Any additional info is also welcome. Thanks

The energy density was calculated using this formula, Energy Density = E/A (J/cm2). Here E is the input energy measured in millijoules, A is the area of the circular spot.

E values I know from LDT analysis.

A value, How to calculate using the following parameters?

Laser Beam diameter= 8 mm

Focal length = 20 cm

Nd:YAG laser = 1064 nm

Pulse width = 10 ns

In a Luminescent Solar Concentrator (

**LSC**), the fluorophores (organic dyes, quantum dots,...) can be embedded either in the waveguide material, in a top or a bottom coated layer. I want to know how does the location affect the LSC performances. Is there any reference treating this issue?Einstein stated that “The same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good”. In general, one of the main principle of SR is that "the laws of nature are the same for all inertial reference frames". Is this statement true?

One simple counter example refutes the above statement. Consider the law of the equality of the angles of reflection and incidence, say, when an ideal-elastic ball is thrown with a specific angle at a flat wall.

The reflection law is not true if the ball movement is studied from a different inertial frame. For example, if the experiment is observed by someone who is moving with the relative speed of

*parallel to the reflection flight of the ball, the angle of reflection is always the same for any angle of incidence. The latter angle depends on the relative speed between the frame and the observer,***v***.***v**In general, the angle of reflection can be smaller, equal or larger than the angle of incidence if observed from different inertial reference frames. Please see section 2.1 (page 4) of the attached article for illustrations and more details.

I am preparing an optical system in infrared, however I will need to stick two optical components. They are made from CaF2.

Can you recommend index matching-liquid? I am interested in the range 1um-15um. I see that other researchers use paraffin oil, but still i would like to make sure of all possibilities.

Or maybe there are few liquids, that would work eg. in 1um-5um, 5um-10um and so on?

Dear Professors,

Can you please send me your paper entitled " A Quantitative Study of the Laser-Induced Ring Pattern and optical limiting From 4-Chloro-3-methoxynitrobenzene solution"

Thank you in advance.

Best regards.

Dear colleagues,

The Z-scan technique is proposed by Sheik-Bahae et al [1]. Theoretically, when there is no nonlinear absorption, the Z-scan curve must be symmetric around the

**origin**of the Z-axis. However, in practice, the Z-scan curve usually has a large asymmetry. I know the reason for this phenomenon for thermal-optic nonlinear mechanisms. For the electronic nonlinear mechanism, what are the reasons for this asymmetric phenomenon? (Except for experimental error). Thank you and hoping for your insightful response.

[1] Sheik-Bahae, Mansoor, et al. "Sensitive measurement of optical nonlinearities using a single beam."

*IEEE journal of quantum electronics*26.4 (1990): 760-769.Dear colleagues,

Without nonlinear absorption, the Z-scan curve corresponding to the pure nonlinear refraction will be symmetric around the origin O. The nonlinear absorption will lead to asymmetry of Z-scan curve. Thus, the closed aperture Z-scan of a material with nonlinear nonlinear absorption and nonlinear refraction give an asymmetric curve. Therefore, we can develop a matlab program to automatically generate nonlinear absorption curves so that these curves multiply with the closed aperture Z-scan curves reproduce a symmetric curve [1]. From this symmetry curve, we can calculate the nonlinear refractive indices, and from the nonlinear absorption curve produced by the matlab program we derive the nonlinear absorption coefficient without the open aperture Z-scan measurement. I have implemented the above idea on closed aperture Z-scan data in works [2] and [3] and found that results perfectly consistent with results in above works. In summary, we can use the matlab program or the numerical methods (fitting curve) generally to determine n2 and beta from the closed- aperture Z-scan data. But why in most works did open aperture Z-scan measurements implement to determine n2 and beta, are this measurements really necessary?

Thank you and hoping for your insightful response.

[1] Beam radius based Z-scan + Matlab method, Link: https://www.researchgate.net/publication/319403552_Beam_radius_based_Z-scan_Matlab_method

[2] Sheik-Bahae, M., Said, A. A., Wei, T. H., Hagan, D. J., & Van Stryland, E. W. (1990). Sensitive measurement of optical nonlinearities using a single beam. IEEE journal of quantum electronics, 26(4), 760-769.

[3] Abrinaei, F. (2017). Nonlinear optical response of Mg/MgO structures prepared by laser ablation method. Journal of the European Optical Society-Rapid Publications, 13(1), 15.

hi there,

how we can compute refractive index of rectangle plates with interferometer, diffraction and polarization methods?

and what is related setup?

thanks.

Dear colleagues,

I have used LBP-1-USB Laser Beam Profiler, Newport. This device can measure two-dimensional and three-dimensional beam profiles as well as measure the beam radius very well. The device can also measure relative power (compare two powers). However, the results are very different from that of the optical power meter. At present, we have made laser beam profiler according to the work of Prof.S. De Iuliis:

However, I still wonder if the laser beam profiler can measure the power accurately theoretically?

I hope to receive your answers. Thank you in advance.

Currently I'm optimising a lens system which needs to have a MTF 50% or over at a certain line pair (e.g. 50lp/mm) across 400 - 700nm. By studying the examples of OSLO software, I didn't find such built-in function to get 50% @ 50lp/mm at 400nm, 550nm and 700nm, simultaneously. How can I achieve it?

Many thanks if anyone can give some suggestions

Dear Colleagues,

I'm studying the Self-defocusing effect in Aniline Blue organic. Initially this material is in powder form. However, to exploit their applications, we have to convert them into a solid film by the free radical bulk polymerization method. However, through observation of organic film, I found that aniline blue did not dissolve well into the solvent. Can anyone explain to me why the aniline blue is not soluble but gives good Self-defocusing effect?

Thank you and hoping for your insightful response.

Dear Colleagues,

I'm studying self-defocusing effect in organic material. In the light beam on the screen, I observe the rings like attached images. Is this the result of diffraction? What is the physical mechanism behind it? And how does it affect radius measurement since we usually measure the radius of a continuous light beam, with no interruptions (at dark rings)?

Thank you and hoping for your insightful response.

Dear Colleagues,

From relation:

P=ε_0 χ^((1)) E

I suppose that in an isotropic medium, χ^((1)) is the scalar quantity, vector P and E are in the same direction, while for an anisotropic medium, χ^((1)) is the tensor quantity, vector P and E are different in direction. However, my professor said that the above statement is not true in some special cases. Could you tell me which is the those cases?

Thank you and hoping for your insightful response.

Dear Colleagues,

I am studying a third order nonlinear optical organic material with a negative nonlinear refractive index, but the total refractive index is positive (n=n0+n2I, n2<0). What does the n2.I / n0 ratio make sense in the third order nonlinear optics? And for organic materials, how much is this ratio ? (according my experience, it is about 1/100000)?

Thank you and hoping for your insightful response.

Dear Colleagues,

I'm studying the third-order nonlinear optical effect in organic material (polymer film of aniline blue, acid blue 29, Oil red O), but I worry organic material has a lower thermal stability and a lower optical damage threshold than that of inorganic. Is the thermal stability and optical damage threshold of organic material really low? Is there a way to improve that?

Thank you and hoping for your insightful response.

There are several types of laser diodes used in the construction of holograms.

Z-scan technique is very powerful and simple in determining both the sign and magnitude of the nonlinear refractive index and the nonlinear absorption coefficient . The original Z-scan was proposed by Prof.Sheik- Bahae et al in 1989 identifying nonlinear coefficients and through a closed aperture Z-scan and an open aperture Z-scan1,2 . This method can be called transmittance based Z-scan. Since then, many variants of original Z-scan technique have been developed to enhance the sensitivity and signal-to-noise ratio. According Prof.T.Godin3, these variants can be categorized into 4 types: alteration of the input beam profiler4,5, theory optimization6, alteration of the detection system3,7-10 or modification of the original experimental setup11-14 .

However, when I read articles on the investigating third order nonlinear characteristics of material, the method often used is Z-scan method of Prof.Sheik- Bahae. Why these variants are not applicable and can not replace the original Z-scan?

Thank you and hoping for your insightful response.

1.M.Sheik-Bahae, A. A.Said, and E. W. Van Stryland, High-sensitivity, single-beam n2 measurements, Opt. Lett 14(17) (1989) 955-957.

2.P. B. Chapple, J. Staromlynska, J. A. Hermann, T. J. Mckay, R. G. Mcduff, Single-Beam Z-Scan: Measurement Techniques and Analysis, J. Nonlinear Optic. Phys. Mat, 6(3) (1997) 251-293.

3.T.Godin, M.Fromager, E.Cagniot, R.Moncorgé and K. Aït-Ameur, Baryscan: a sensitive and user-friendly alternative to Z scan for weak nonlinearities measurements. Opt. Lett, 36(8) (2011) 1401-1403.

4.W. Zhao and P. PalffyMuhoray, Zscan technique using tophat beams, Appl. Phys. Lett. 63 (1993) 1613.

5.S. Hughes and J. M. Burzler, Theory of Z-scan measurements using Gaussian-Bessel beams, Phys. Rev. A 56(1997) R1103.

6.R. E. Bridges, G. L. Fisher, and R. W. Boyd, Z-scan measurement technique for non-Gaussian beams and arbitrary sample thicknesses, Opt. Lett. 20(1995)1821.

7.T Xia, M Sheik-Bahae, AA Said, DJ Hagan, Z-scan and EZ-scan measurements of optical nonlinearities, J. Nonlinear Optic. Phys. Mat, 3(04) (1994) 489-500.

8.A. O. Marcano, H. Maillotte, D. Gindre, and D. Métin, Picosecond nonlinear refraction measurement in single-beam open Z scan by charge-coupled device image processing, Opt.Lett. 21(1996)101.

9.G.Boudebs, V.Besse, C.Cassagne, H.Leblond, and F.Sanchez, Why optical nonlinear characterization using imaging technique is a better choice?, In: Transparent Optical Networks (ICTON), 2013 15th International Conference on. IEEE ( 2013) 1-4.

10.G.Tsigaridas, M.Fakis, I.Polyzos, P.Persephonis and V.Giannetas, Z-scan technique through beam radius measurements, Appl. Phys. B 76(1)(2003) 83-86.

11.G. Boudebs and S. Cherukulappurath, Nonlinear optical measurements using a 4 f coherent imaging system with phase objects, Phys. Rev. A 69(2004) 053813.

12.D. V. Petrov, A. S. L. Gomes, and C. B. De Araujo, Reflection Z-scan technique for measurements of optical properties of surfaces, Appl.Phys. Lett. 65(1994)1067.

13.H. Ma and C. B. De Araujo, Two color Z-scan technique with enhanced sensitivity, Appl. Phys. Lett. 66(1995)1581.

14.A. A. Andrade, E. Tenorio, T. Catunda, M. L. Baesso, A. Cassanho, and H. P. Jenssen, Discrimination between electronic and thermal contributions to the nonlinear refractive index of SrAlF 5: Cr+ 3, J. Opt. Soc. Am. B 16(1999) 395.

Is it possible to lock the laser to fabry perot interferometer resonance curve negative slope (at half power point) by electrical feedback of transmitted signal to laser drive current source.

In Z-scan technique, we often use motor (digital mcrometer transformer) to move sample. I think that motor is ued to automate measurement. If there is no motor, for example, we can move sample manualy on bar (marked by lines seperating 1 mm, sample is placed on holder, holder can move on bar), we determine position of sample by reading lines on bar, and get laser intensity on detector.

So is it necessary to use motor ? Can we move sample by hand ?

Thank you and hoping for your insightful response.

Dear colleagues,

As far as I know, reverse saturation absorption is one of the mechanisms of optical limiting effect. Because when the light intensity is strong, the absorption coefficient increases, that is, light is absorbed more strongly by third order nonlinear optics material. So when we illuminate the material, initially when the input power increases, the output power behind the material also increases. At certain threshold, the output power is saturated. However, I'm not sure whether nonlinear refraction (nonlinear index n2) is the mechanism that causes the optical limiting or not. The nonlinear refraction only cause the beam to diverge or converge, only changing the light intensity without changing the power.

So, the issue is: Is the nonlinear refraction one of mechanism that causes the optical limiting effect?

I am looking forward to hearing from you.

Dear colleagues,

Recently, we have seen many studies on third order nonlinear optical effects and optical limitting in organic with CW laser. Some researchers wonder whether these effects are within the scope of the nonlinear optics or just thermal effects? Because, in these studies, wavelength of the laser is strongly absorbed by organic materials. And the self-focusing or self-defocusing effects occurs simply due to absorbing effect and heat is formed. Should we consider these effects as nonlinear optics effects? Any materials absorbing wavelength of the laser have self-defocusing effects. So are these effects is important? I think that these effects are nonlinear optics effecs because n2 depend on intensity and some materials absorbing wavelength of the laser don't have self-defocusing effects.

What is your point of view on this issue?

Dear colleagues,

I have read many papers on Z-Scan measurements of material, I see that the error is in the range of 25 to 40%. Some authors claim that the error is up to 50%. And the measurement of nonlinear index n2 by Z-scan and other methods are sometimes a difference of more than one order of magnitude. So which range the error of the Z-scan method lies in? And how many order of magnitude do results of measuring nonlinear index n2 by Z-scan method and other methods such as THG, EFISH, DFWM different?

I am looking forward to hearing from you.

I used femtosecond laser to do ablation in producing silver nanoparticle. In order to create the good coloid, i have to make the beam focused, how can i get the new focused beam in medium? How to calculate the new focused beam size, so that the focused beam touch the silver plate

Hello everyone.

there are different type of relationship to calculate the phase matching angle, I bring two of them in attached, which I can derive the second one. and we found that the first phrase (phase matching condition ) is not true. I need to derive the irradiance of frequency doubled beam varies with theta when phase matching condition is not obeyed (the yellow part marked in the picture).

I will be grateful to anyone can help me.

Best regards,

Hi everyone,

What configuration of lenses is utilized to make light sheets for imaging purposes?

form the image in circular phantom in diffuse optical imaging

Is there a concept of optical oscillators (like an electronic LC oscillator) or a tunable laser can be used as an oscillator?

I want to measure the retardance and diattenuation for a set of retarders and polarizer at visible wavelenghts. I would like to know what are the methods and devices to measure those properties.

I am quite flexible about the number of screws and the shape of the mount as long as the diameter is around 0.5".

Generation of visible light can be achieved using SFG of two sources in the IR. I am looking for information on the viability of generating orange light by SFM of 1550 nm and 980 nm pump sources.

Whether magnitude of conservative backscattering in a RLG is constant or if it varies over time?

I have UV blubs of a 1000 µW cm-2 , can i reduce the intensity of the light to 650 µW cm-2 which my experimental cells will be exposed to by changing the distance from the source of light ? If yes how ?

if in chromatic confocal sensor, a led with low coherence and a multi-mode fiber are used. I wonder this imaging process should be the which one ? In the monograph about fiber optical confocal scanning microscopy by GuMin, he treat the imaging process as totally coherent imaging when a laser and single-mode fiber is used.

Does anybody know a good paper/resource where one has measured the influence of a tilted/shifted mirror or beamsplitter in an michelson interferometer or OCT-setup?

I'm trying to investigate the effect on the systems contrast.

Maybe somebody has some experiences already.

Many thanks in advance!