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Hello,
I wanted to enrich my knowledge about nonlinear optics and quantum technologies. Are there any resources to study them?
Thank you.
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rp-photonics.com - simple explanation + references for more detailed study
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I have been trying to understand the second and third-order nonlinear processes (specifically SHG and two-photon absorption). I am still unable to understand how the order of these nonlinear processes is determined. I was unable to find adequate information about this in the Nonlinear optics by Robert Boyd. Please help me understand this, or suggest me a source to study more about it.
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Shiva Mahmoudi In two-photon absorption, the system absorbs 2 photons, and while relaxation, 2 waves are emitted - a signal wave and an idler wave, resulting in a total of 4 waves.
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Hi
i am Dhanya, a research scholar from kerala university.
i am studying non- linear optical properties of a set of compounds using DFT with functional B3LYP and basis set 6311G (d p)using Gaussian 09 software. Upto my knowledge i believed that if a compound having good NLO properties, it has low HOMO - LUMO gap and high hyperpolarizabilities.
i calculated HOMO - LUMO gap and hyperpolarizabilities. But in the case of set of compounds of my study, the decreasing of HOMO - LUMO gap and increasing of hyperpolarizabilities are NOT IN SAME ORDER.
What should i do?
please help me🙏😔
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Although it is true that compounds with a narrow HOMO-LUMO gap often display large hyperpolarizabilities (beta) and hence second-order NLO properties, the HOMO-LUMO gap is not directly proportional to hyperpolarizability and therefore it is not expected to follow the same trend.
So if you are interested in NLO you have to calculate beta values, there are no shortcuts. In Gaussian this can be done within a vibrational analysis (freq=Raman). I and my coworkers have published a couple of papers regarding NLO properties of metal complexes. An example is this:
I hope this may help.
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Hello everyone,
I did some research on the internet about analogies between nonlinear optics (NLO) and general relativity (GR), e.g. https://arxiv.org/pdf/0711.4796.pdf. That's already a very nice result, but is it possible to go even futher? It's a stupid idea, but since both GR and NLO are nonlinear field theories, is there any mapping between these two say at least for special solutions to the Einstein field equations? So more generally asking: Is it possible to simulate and study black holes (or other GR scenarios) with nonlinear optical setups in a earth-based laboratory? I'm really excited about this. Thanks a lot!
Philip
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A recent overview, ``Optical analogues of black hole horizons", might be useful, too:
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I want to take second harmonic generation measurement of nanofibers.so please suggest any institute where this facility is available in india .
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Please contact
Dr. Shankar V. Nakhe
Director
Raja Ramanna Centre for Advanced Technology
P.O.: CAT
Indore - 452 013
M.P. (India)
Phone: +91-731-2321341
Fax: +91-731-2321343
Email: director (at) rrcat.gov.in
They work with nanofibres and have the expertise and the necessary equipments and set-up to check the SHG output of your nanofibres.
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I want to take second harmonic generation measurement of nanofibers .So please suggest any institute where this facility is available in india.
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You can contact the following address given below whose website is www.cccm.gov.in
and the section is - Laser Spectroscopy Section, was Headed by
Dr.M.V. Suryanarayana - Professor, HBNI, Senior Scientific Officer ( who is presenting working in a different division of BARC) suryam@barc.gov.in and contact number 9440128283
or his colleague
Sri. P.V. Kiran Kumar, Scientific Officer (G) kirancccm@gmail.com
National Centre for Compositional Characterization of Materials (NCCCM)/BARC,
E.C.I.L (P.O),
Secunderabad- 500 062.
Department of Atomic Energy.
They have Secondary Harmonic Generator (SHG) option for their pump laser. They have DPSS pumped Ti:Sa laser and dye lasers, diode lasers etc. You can discuss the exact wavelength of the first harmonic ( primary wavelength) which has to be doubled using crystals like Lithium Niobate,BBO, KDP which they have at present in their laboratory to the required SHG wavelength that you are looking for.
Good luck.
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What could be the applications where the presence and control on the fifth-order nonlinear optical susceptibility could be essential or advantageous?
Thank you.
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Extremely high order harmonic processes are used to generate ultrashort pulses for attosecond physics. I think harmonics up to the 30 or 40 or even 50 range (odd numbers ofcourse) are quite often used to generate attosecond pulses in the extreme UV range.
Specifically fifth order processes, I am unaware of. As far as I am aware most nonlinear spectroscopy or microscopy applications can conveniently achieved in the third order. So, in case you don't have a new scheme, I can't benefits right now.
Even if a fifh order process would be interesting, probably a cascaded second or third-harmonic process will still be more efficient.
Just my first thoughts on the questions.
Regards,
Michael
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I want to generate second harmonic using the long-wavelength (1600nm) part of the supercontinuum as pump. How to decide on choosing the right focal length lens for SHG. I am using 10mm-long MgO-PPLN. The average power at the output of supercontinuum is ~100mw and ~40mw for SHG (after long-pass dichroic mirror). Since the temporal profile of the signal after SC is not known (specifically for the 1600nm part ), is it suitable to treat that signal as continuous-wave for SHG pump. For CW pump, the literature suggests that the ratio of crystal length to the confocal parameter (2*Rayleigh range) should be 2.84 for optimal SHG. From where we may calculate the right focal length of the lens to focus light into the SHG crystal.
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you welcome Abbas N..
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I am wondering if it is possible to measure mode-locked laser stability (timing jitter, Noise) with an oscilloscope if the pulse duration is in the femtoseconds regime (lets say 150fs). If so, what type of measurement on an oscilloscope would quantify laser stability. What should be the bandwidth of the photodetector and oscilloscope?
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I concur with Ahmad Adel Alsakati
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Where could I find some numerical results of the P(beta) (power vs effective index) characteristic related to a single layer nonlinear optical waveguide with lambda=0.515 microns, df=1micron, nc=1.55, nf=1.57 and ns=1.55 with nonlinear (Kerr) cladding coefficient n2c=1e-9 or other ? I simply need numerical data for comparison with my method.
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Hello
by using COMSOL Software Programm
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I am using the experimental scheme presented in the image below. It seems that no matter what I do, I cannot obtain coincidence counting higher than 350/s, although the single count at each detector is about 500000/s. The crystal used is a 2 cm long 10 um period PPKT collinear type II crystal.
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I would suggest to verify the temporal synchronization of the two detectors. For a too narrow coincidence window and different latency of the detectors, the true coincidences might be outside of the coincidence window. Only false (random) coincidences are present. The first step would be to increase the coincidence window to dozens of ns to surely cover any difference in latency. Then you can start decreasing the coincidence window and adding a delay to the fastest detector channel, e.g. using time tagger functionality or simply extending the length of a coaxial cable.
Also, it might be useful to add cut-off filters transmitting the red signal and stopping the blue pump in front of the detectors. Using the filters you make sure that your signal comes from the SPDC process and not from the laser. Filters https://www.semrock.com/filterdetails.aspx?id=blp01-633r-25 are very good but you can use any low-cost alternative.
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I have generated an octave-spanning supercontinuum (750-1700nm) using 140fs pulses. I want to frequency double longer wavelength (1600nm) using PPLN crystal. Since, I don't know what's the pulse duration/shape, peak power, or energy in that specific bandwidth (around 1600nm), how should I choose SHG crystal (PPLN) for SHG. Specifically, how to determine crystal length and acceptance bandwidth for optimal SHG at 800nm.
Thanks in advance.
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Dear Prof. Walid Tawfik , I want to convert 1600nm to 800nm using SHG crystal.
Thanks for the link you have provided.
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Does anybody know what is the maximum power of laser sources (QCL, VECSEL, and so on) in THz regime?
I'm trying to realize a nonlinear effect in THz regime using a THz source without using DFG or SFG. I need 200 mw or more for my device. Is it doable? is there any source to generate that power?
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Dear
Farooq Abdulghafoor Khaleel
Many thanks for your response and valuable information.
TOPTICA Photonics has unveiled some commercial THz sources with 0.1-6 THz spectrum in mW range.
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For example, I would like to simulate nonlinear response from the linear response simulation for plane wave incidence at an angle. I know that using Lorentz reciprocity, we can obtain it and there are papers for normal incidence case. One such case is described by DOI: 10.1038/NMAT4214. But this method is only described for normal incidence case. What and how should we modify it for the off-normal incidence case.
I would like to explain experimental SHG results of periodic metasurface for angled illuminations.
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Naively, I would say that the intensity simply scales with the cosine of the incidence angle, but one probably has to be a bit more careful here. If you know the complex-valued refractive index of your metamaterial, you can simply apply Fresnel's equations to determine the field strength and intensity inside the material for arbitrary incidence angle.
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In general, it is not possible to observe simultaneously all nonlinear effects described by the nonlinear polarizations, because usually only one nonlinear process is phase-matched.
In nonlinear nano-optics, since the wave phase-matching between interacting optical fields does not affect the nonlinear optical interactions, is it necessary to achieve phase-matching ?
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At nano-scale, the phase-matching can be replaced by the overlap between the resonances for the interacting wavelengths (both material resonances and resonances due to the geometry of any present nano-structures). Have a look at this paper: https://www.nature.com/articles/s41467-018-04944-9
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Can anyone tell what is the reason of these sharp frequency modulation in SPM broadened power spectrum. This is the spectrum of mode-locked laser with 0.4nm initial bandwidth at 1064nm. After amplification to 400mW (in YDF) and propagating through 6m length of PM-980, such spectrum appeared. I am wondering how to get rid of these modulations to enable efficient pulse compression.
Pls see the attached picture.
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As far as I can see, you are showing the spectrum on a log scale, but these oscillations are essentially a hallmark of the SPM, and you can estimate the total accumulated nonlinear phase from the number of the spectral oscillations. This was observed for the first time by Roger Stolen in the 1970s:
Self-phase-modulation in silica optical fibers
R. H. Stolen and Chinlon Lin
Phys. Rev. A 17, 1448 – Published 1 April 1978
A more detailed discussion can be found in the textbook by Govind Agrawal, Nonlinear Fiber Optics. I would estimate the total nonlinear phase in your fiber as about 3.5 \pi.
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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!
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The famous equation is: \tau_compressed [ps] = 0.05 \sqrt( \tau_in[ps] )
Dianov et al. Efficient compression of high-energy pulses, IEEE J. Quantum Electron. 25, 828 (1989).
Another good reference is: W. J. Tomlinson and W. H. Knox, Limits of fiber-grating
optical pulse compression, J. Opt. Soc. Am. B 4, 1404 (1987).
So you can expect best compression to about 100 fs, and this may already prove to be quite a challenge.
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how to do f-2f interferometry from an octave spanning supercontinnum with frequency spacing 120MHz. Which would be the most suitable optical filter in this range for filtering f and 2f components from supercontinnum, to detect carrier envelope offset frequency of a mode-locked laser.
Thanks in advance!
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The optical filter has to be matched to the phase-matching bandwidth of your SHG crystal. For Ti:sapphire based combs, one typically uses some off-the-shelf PPLN crystals, e.g., for 532 nm wavelength. You can find matching interference filters from Thorlabs or Edmund Optics. You can also use a simple diffraction grating instead. Details on a suitable setup are here: https://www.nature.com/articles/nphoton.2010.91
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Is there a simple proof that the signal and idler photons created by spontaneous parametric down-conversion (SPDC) are entangled, whereas those that are created by optical parametric amplification (OPA) are not? SPDC has been used in the optical band to create entangled photons. A view of this is that the SPDC just amplifies the vacuum (zero-point energy) photon to create a signal photon, whilst an idler photon is created to preserve conservation of energy when the pump photon annihilates. In the OPA process a seed photon is parametrically amplified likewise to create a signal photon and idler photon, whilst the pump photon annihilates. What is the proof therefore that the signal and idler photon pair from OPA are not entangled?
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Hi Paul,
thank you for that, yes agreed.
I'm happy that SPDC signal and idler are entangled, so now 'all' that is needed now is some mathematical proof to show that OPA signal and idler photons are entangled or not.
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I am working on crystal growth of nonlinear optical materials. So I would like to carry out second harmonic generation (SHG) measurements by kurtz and parry powder method. So please suggest any institute or SIFE where this facility is available in India and abroad also.
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VIT chennai and vellore also the same facilities and third harmonic also
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Dear Colleagues,
I'm studying the optical limiting effect in organic material due to reverse saturation absorption. As we know, in reverse saturation absorption, the transmission coefficient decreases as the intensity increases, or the absorption coefficient increases as the intensity increases, resulting in power loss. So, when we increase the laser power to a threshold P0, there are two competing processes: the increase in input power and the power loss due to reverse saturation absorption. If these two processes are in equilibrium, the optical limit curve is horizontal (as in the attached pictures.) However, if the amount of lost power is greater than the increase in input power, the curve must go down at P0. Why in the paper on optical limiting don’t we  see such cases?
Thank you and hoping for your insightful response.      
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The absorption coefficient of a material showing RSA will increase when the input optical fluence is increased. However, the processes underlying RSA (mostly excited state absorption in organic molecules) do not result in the absorption of more light than what is fed into it. Therefore, the scenario you envisage will not happen.
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BER analyzer parameters meaning.
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The reliability of data transmission characterizes the probability of getting a distortion for the transmitted data bit. This indicator is often referred to as the Bit Error Rate (BER). The BER value for communication channels without additional means of error protection is 10-4 — 10-6, in optical fiber — 10-9. A ber value of 10-4 indicates that on average, one bit is distorted out of 10,000 bits. The q-factor of the receiving system Q is determined from the expression:
Q = GA/TC,
or, in logarithmic form:
Q[dB] = GA[dB] - 10lgTC[x].
It is the q-factor of the receiving system that determines the signal-to-noise ratio (C/N) at the output of the low-noise Converter (LNC or LNB). It is important to note that the final C/N value does not depend on the LNC gain.
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In absence of phase matching constraints (in a microscopic framework), are the quadratic SFG and DFG processes bonded together ? (Assuming you illuminate with two frequencies) is there an ultimate relative efficiency limit?
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Ok, is the local probability of two photons to undertake SFG and DFG in a quadratic system always the same (from the nonlinear coefficient expansion in the nonlinear quandratic hamonic oscillato)? My question mostly points to if a system in which significant SFG is taking place always requires significant simultanous ongoing DFG (off course I am not referring to the phase matching role in selecting a process)
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Hi,
I am studying effects of Spin orbit interaction in nonlinear optical responces espesially SHG.
I want to find relationship between spin-orbit effects and the second harmonic generation(SHG) response in nonlinear optical crystals.
any one who can guide me?
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In recent research perspective this is very important field. Parity operation is reversal of co-ordinate (x->-x, p->-p)and time reversal operation is reversal of time (x->x,p->-p, i->-i).
But talking about this combined PT-symmetry in any field of science and engineering, what it implies?
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Dear Prof. Samit Kumar Gupta,
In superconductors, a PT symmetry invariance broken state could be the main manifestation of anionic superconductivity. There are not agreements so far on the subject.
Please see this external reference:
Selected Topics in Superconductivity by L. C. Gupta, M. S. Multani
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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.
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what is the effect of the increases of the number of rings
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How to calculate two photon absorption cross section and two photon emission cross section of dyes?
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Hi, you can using this research
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As far as I know, the phenomenon of lasing is considered in nonlinear optics whereas the emission is considered in linear optics. But I don't know why. Can anyone guide me on this?
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An excellent presentation of physical insights,
thank you very much, Michael Belsley! I suggest that you may be interested in seeing some of my work: at least these three (3) files
(Click Download to get 4 May 2020 PREPRINT#4)
Video: https://tinyurl.com/uajcnxx (open in a video player)
and whatever else that may interest you in folder https://tinyurl.com/to8tsbt ;
I also hope that you will share with me any thoughts you may have about how I could improve any aspect of my work; or, how my work relates to yours.
Please enjoy the attached art, which was created during study of the above-referenced video.
With all best wishes for your own successes! :-) -Steve- gambist@gmail.com
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What is the best non-linear material?
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Hi, Ban A. Naser! I hope that you and your family are well.
Although others seem to comprehend what you are doing and what materials might be best, I empathize with the the question asked by Ali Hussain. To me, the best "non-linear material" I could find has been the freshest of the course-grained rock samples that I collected from the Island of Maui, Hawai'i. The non-linearity of refractive indices (RIs) displayed by a powder from that sample can be appreciated by accessing and studying at least these three (3) files
I hope that you will enjoy the attached art, which was created during study of the above-referenced video.
With all best wishes! :-) -Steve- gambist@gmail.com
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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)
Please advice.
Thanks
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Abbas N. regarding your 3 points:
1) There is no need for the lens NA to equal that of the fibre. Usually, coupling will be more efficient if the lens NA exceeds that of the fibre, provided the lens aperture (entrance pupil) is sufficiently large to avoid vignetting the input beam.
2) Coupling is optimised when the beam is focussed to a spot whose field profile matches the field distribution of the fibre mode. Typically, both launch spot and mode profile are approximately Gaussian, and the matching criterion is for the launch spot diameter to equal the mode field diameter.
3) Launching the collimated input beam parallel to the optical axis of the lens which in turn is coincident with the optical axis of the fibre will minimise mode mismatch due to tilt errors and lens aberrations.
More specifically, you specify a beam quality factor M2 = 1, so the beam is close to an ideal Gaussian beam. When focussed by a lens, the radius of the beam waist at 1/e2 intensity, w0, is related to the wavelength, λ, and the divergence half-angle, θ, also at 1/e2 intensity by: θ = M2 λ / π w0
Your collimated input beam width is W=0.65 mm. If the focal length of the lens is f, the radius of the beam at the lens principal plane is W = θ f = f λ / π w0
provided the lens NA > sin θ. https://www.newport.com/n/gaussian-beam-optics
The fibre mode field diameter will be comparable to the fibre core diameter, but need not be identical. The relationship depends on wavelength, and the extent to which the evanescent field extends into the cladding.
If we assume that the beam spot radius is equal to the fibre radius, w0 = a = 1 μm, then we require a lens focal length f = π W w0 / λ = 1.98 mm.
A larger mode field diameter will require a proportionately larger focal length. A 2.8 μm mode field diameter will require a focal length of approximately 2.8 mm. The exact value is not too critical. If the mode field radius is r0, the coupling efficiency (assuming Gaussian profile for both fibre mode and excitation) is:
η = 4 w02 r02 / (w02 + r02)2
A 40% mismatch between launch spot diameter and mode field diameter degrades the theoretical coupling efficiency by only 11% (to 89%).
Regarding the choice between microscope objective and aspheric lens, both are capable of diffraction-limited performance for a monochromatic beam aligned with the optical axis. The microscope objective will be more complex, because it must deliver high resolution imaging over a relatively wide field of view, with illumination comprising a broad range of wavelengths.
The exact focal length of microscope objectives is not always stated. Magnification depends on the distance between objective and eyepiece. Tube lengths of order 160 mm are common, so a crude estimate for high power objectives is focal length f = 160 mm / magnification.
The 60x objective suggested by Suchita Yadav. would have a focal length around 2.7 mm, and would be a reasonable choice, especially if the fibre MFD is larger than 2 μm, but an 80x objective may be better. A 40x objective with 4 mm focal length is probably be too long.
If the microscope objective is optimised for visible wavelengths, there may be some additional losses due to surface reflections at infra-red wavelengths.
Note that a weak supplementary lens can be used to modify the diameter of the beam as it enters the focussing lens, and adjust the spot size for optimum coupling.
Hope this helps.
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Hello dear researchers,
I want to measure the value of the third-order nonlinear susceptibility (Chi3). I have only the third harmonic generation (THG) spectra in photon counts and I know the input power at the sample to be probed. In literature, people used some materials whose Chi3 is already known and after comparison, they gave a rough estimation of chi 3. The other way in the literature was used is the utilization of an additional laser to calibrate the power.
I would like to ask is there any other way to measure the output power or chi 3 value? any simpler way if you know the input power and output intensity in photon counts???
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I have been using Degenerate Four-wave mixing technique to measure the third-order nonlinear susceptibility. In this technique, I isolate the signal and then measure the signal power with a sensitive photodiode sensor. I calculate back chi(3) using this measured signal power along with my input powers which has been divided into two pumps and a probe. Raul Rangel-Rojo Kaleem Ullah
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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
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Hi Abbas
I have the same question! I am trying to fabricate SMF-GIMF-SMF structure for sensor application. I tried many times to splice the fibres. I manipulated with different splicer parameters as prefusion time, overlap, arc power and so on, but almost always I got splice with a black vertical line (fig. 1).
Once I got good splice. It happened when I accidentally broke the bad splice and respliced it again. Unfortunately, I could never repeat it.
At fig.2 you can see two spectrums. The blue one corresponds to SMF-GIMF-SMF with both bad splices. The red one corrensponds to SMF-GIMF-SMF that have one good splice. The second spectrum had a much better contrast then the first one. This is due to the fact that the modes in GIMF fibre are more equally coupled to the SMF fiber. Thus, there is a difference between coupling coefficients of modes in GIFM to SMF fibre for the "bad" and "good" splice.
P.S. Abbas, please, let me know if you will find a method, how to splice it without bubbles and black curves!:)
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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.
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Dear Nguyen, I beg You pardon, please read with attention my above given advice.. or at least tell us for what task You are going to apply TPA excitation then it would be possible to figure out correctly what laser beam intensity W/mm2 You was needed...
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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.
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Nguyen, It seems reasonable that the greater the absorption efficiency the greater the release of ROS. This applies to both exogenous photosensitizers and endogenous porphyrins. We are preparing a paper describing the absorption spectra of intact, live planktonic pathogens, both bacteria and fungi, collected with diffuse reflection spectroscopy. (Please see our papers: "The Black Bug Myth" and "Selective Photoantisepsis" posted on RG). I propose that these absorption spectra, if obtained in vivo, will mirror the action spectrum (clinical efficacy VS WL) of the clinical application.
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Nonlinear optics becomes important at higher intensities. I wish to know how large laser powers and intensities have been achieved so far.
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Hello Hari,
Just to add another link: Probably the laser with the highest peak power, which by the way does NOT rely on beam combination is the ELI - NP laser in Romania. That is a a system having roughly 10 Peta Watt of power and should deliver about 1E23 W/cm2 at the focus.
There is a very similar system in China which name I forgot.
Best Regards
Marcus
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I work in the transport of information by optical fiber. I have to draw in 3D in the time domain, and in the spectral domain with the frequency.
First, I want to draw the input signal and the output signal as a function of time. Then take them both out in the same graph to compare them. Secondly, I want to trace the evolution of the pulses as a function of the optical distance z and time on the one hand, and on the other hand, I want to trace the evolution of the pulses as a function of z and the diffraction.
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Hi Tomasz,
In chapter three, the part on the list of examples of the document below, I can not open the entire file in .m format. And I have a question, in the "list of examples" , where you plot the power as a function of time, is the red curve the input function and the blue the output function? http://ufs.edu.pl/index.php?article=hussar&lang=en
The current version with a few bug fixes and several new features. (manual for version 1.3) .
Hussar 1.3 software manualTomasz M. Karda ́sJuly 26, 2018.
Thank you.
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Hi,
this is a question about nonlinear optics.
It was suggested by Bloembergen in 1963 that the number of modes of the fundamental laser N influences the Second-harmonic intensity with a factor (2N-1)/N.
It was then checked experimentally by François 1966, but I still can't understand the reason of this factor which is statistical I guess.
Thank you for your time.
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I guess the cited N. Bloembergen math relation pinpoint that that intensity in nonlinear processes (like SHG) will increase non-linearly with incident intensity but without violation the energy conservation law. You could know, for example, that under self-focusing output intensity exceeds multiply the incident one. As for SHG in the phase matching conditions increasing number of mode are followed by decreasing of efficiency because to growth of beam divergence and spectral width (one by one or both).
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In recent days, many research articles are being produced with studies on dielectric behavior and the third order nonlinear optical properties of the materials. Can anyone explain what can be the possible relevance of dielectric studies for third order nonlinear optical applications?
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Dear Hegde, the query is nice. As you know, dielectric properties are well connected to refractive indices. Apart from this, permittivity is directly related to refractive index. Hence, if we have an understanding about these properties with respect to NLO, we can tune them according to our choice.
As a result, we can find their application in Drug delivery, molecular sensing, luminescence etc.
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Hi, I have been working calculating the non linear optical properties of several molecules with Gaussian ('09, revision C), and in the outputs I have some values that represent the non linear parameter (in this case, γ) in several directions (e.g. γxxxx or γxxyy). I have read some papers that present "average values", like <γ>, that are defined with the sum of some of these, but I'm interested in obtaining the magnitude of the tensor, not an average. As the hyperpolarizabilities are tensors the procedure is a little bit more complicated than with vectors, and I have not found an easy way to calculate it with the values printed by Gaussian. Someone can recommend me a paper that explains this, or even tell me the correct procedure to get it?
Thanks.
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The equation for calculating magnitude of second hyperpolarizability (γ) can be found in Section 3.200.7 of latest version of Multiwfn manual. The latest version of Multiwfn is able to directly calculate this quantity based on output file of polar=gamma task of Gaussian, an example is given in Section 4.200.7 of the manual. Multiwfn code and its manual are freely available at http://sobereva.com/multiwfn.
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Because i'm new to the Gaussian user. Thank you.
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Melek Hajji Thank you for your guidance ya.
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Rogue waves are an important topic in water waves, plasma physics, nonlinear optics, Bose Einstein condensate and so on
How can we predict a rogue wave?
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Are you interested in theoretical aspects? If yes, decouple your system in the form of a dinNPDE. Apply preferably numerical simulations to see the wave amplitude behaviours, and so forth. Have a needful comparison with the latest reports on it.
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I have discovered an optical media where slight change in configurations or adding another material in same pattern lead to system to be self-defocusing from self-focusing ( I can't be specific here). What parameters determine the self-focusing and self-defocusing nature of the media?
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That depends upon what is causing the focusing/defocusing. In some use cases, changes in focal length are caused by thermally induced changes to the index of refraction of the material. In other use cases, changes in focal length are caused by the thermal change in shape of the optical elements. I have seen both.
In your case, if the cause is thermal, I would lean toward index of refraction changes. These can be either negative or positive with temperature, depending upon material in question. There are even commercial lenses which use this phenomenon to cancel thermal focal shift. I would guess you are using two materials with opposite changes of index of refraction with temperature.
Note that there are a lot of other things that could be causing this, as well. If you can supply more info, please do.
Good luck!
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One of the recent researches suggests to use the optical modes to carry different channels (with different content, modulation). What are the limitation of using such multiplexing technique? I would appreciate any related book or papers.
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MDM limitation in general is the modal dispersion and the receiver complexity.
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The synthetic crystals of lithium niobate and beta barium borate (BBO) were designed specifically to have the lowest possible power thresholds for nonlinear effects for use in quantum optics. Was the design strategy for these only to develop a crystal with a unit cell that had the highest possible electric dipole? Of course the crystal needs to be transparent and have suitable refractive indices for phase matching, but were these the only design principles, or were there other metrics and parameters for these crystals that needed to be optimised?
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Unfortunately, I have no significant information on BBO. I can only imagine, that the story is similar, i.e. several compounds including LN were competing and BBO stayed persisting due to not only its nonlinear coefficient, but a combination of various practical and technical considerations (Growth, stability, etc.) as well.
Zachariasen was a mineralogist by profession, i.e. he studied geology in Oslo. But his work would from todays perspective probably considered solid state physics. He did systematic x-ray diffraction analysis.
His PhD thesis is called " Untersuchungen über die Kristallstruktur von Sesquioxyden und Verbindungen ABO3", which is in german. Translated it means something like: "Investigation on the crystal structure of sequioxides and compounds of ABO3 type". Sesquioxides are materials of the general chemical compounds A2O3, where A could be things like Al and O is oxides, while ABO3 are things like A=Li and B=Nb etc. His thesis is about x-ray diffraction analysis of as many compounds as possible of these groups to find structural rules etc. The only thing you can find online readily are summaries of his thesis:
As far as I understand it, he did grow (or got someone to grow) LiNbO3, as I am not aware of its natural occurence. Early works on the structure of LiNbO3 point to the early works of Zachariasen as early work on the crystal structure. Compare Abrahams for example:
Anyway, the early works by Zachariasen is only an interesting side-note. Zachariasen never noted the polar structure or ferroelectricity. This was noted by Matthias and Reimeka, who noted this:
by the way: While LN is used for nonlinear devices and not really designed for large nonlinear coefficients, there is work trying to optimize compounds for ultra large second order nonliearities or electro-optic coefficients. This has been done for polymers, because in chemistry and with large molecules, there is more flexibility in designing specific properties.
If you just compare the nonlinear coefficients of these molecules with LN, you will find 100 or 1000 times higher nonlinearities easily. By the way, you may now ask, we we are not using nonlinear polymers. People have built extremely efficient nonlinear frequency converters or electro-optic modulators out of this. But polymers have one big issue, which is stability. Large molecules tend to decompose or change their chemical structure under UV light, heat or ambient chemical enviromements. In contrast to this, LN as a crystal stays stable for years. Even domain structures stay stable for years. LN is relatively resistant to scratches, it melts only a way above 1000°C etc. But again, LN is not without its problems. Just search for research directed to address LNs photorefraction (which I think is also one field, where BBO comes in. It takes more power; This is also one of the reasone, why still alternatives are researched, such as KTP). Another limiting factor of LN are the huge mode sizes in indiffused waveguides in bulk samples. This leads to an ultimate limit in its conversion efficiency or requires huge voltages in modulator. However, the advent of thin film LN has addressed this issue. Just compare these two recent articles:
A further issue is the smallest poling period for quasi-phase matching, which can be achieved. Currently there is a lot of interest to get sub-micron domain periods, which can be used for counter-propagating frequency conversion processes. However, this has not yet been shown in LN, however in KTP. Check the work by Canalias:
I hope, I could help you.
Regards,
Michael
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I am looking for the Non linear optical parameters of Calcite and Quartz crystals in the telecom window (1.2 - 1.7 micrometer).
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Thanks a lot Prof. Gagik G. Gurzadyan.
All the best
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Can anybody please suggest a tool in which non linearity of optical material can be modeled.
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Hi,
I don't know your application however a very good source for the 2nd order nonlinear effects as well crystals is SNLO software (http://www.as-photonics.com/snlo). And its completely free.
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If metamaterials could be designed to have non-linear susceptibilities (magnetic or electric) and phase matching properties for the refractive indices in the mm-wave band they might enable novel quantum processes. In naturally occurring dielectrics non-linear susceptibilities arise in non-centrosymmetric crystals. Perhaps something could be synthesized in synthetic materials. There might be magnetic counterparts to this. Scientists working on metamaterials must have considered this, so where is this at the moment? Comments welcome. N
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Sebastian and Rajib, thanks, those are interesting papers, Cheers, Neil
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Considering that water molecule is asymmetric , does it show significant optical chirality?
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I think it's worth noting that magnetically induced rotation of linearly polarised light, mentioned by Nikolay, is not chirality. The difference is obvious in the optical isolator, where optically active materials cannot be used.
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I'm trying to perform NLO properties calculations with Gaussian and I need to calculate first hyperpolarizability. I faced in literature with static and dynamic ones. Can anyone explain the main difference between them? And which one is more important in such calculations? Thanks in advance!
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Mr. Kulichenko,
Static polarizabilities are determined within the framework of the effect of the external electric field. Frequency dependent polarizabilities are the so-called dynamic polarizabilities.
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I have performed an experiment to frequency mix 974 nm LD laser and a C-band ASE laser source in a single period (10.2 um) MgO:PPLN. I however noticed five peaks at 487, 536, 598, 756, and 816 nm wavelengths detected with a fiber spectrometer. Whilst the 487 and 598 nm outputs could be second-order SHG of 974 nm and SFG (974 nm+~1550 nm), respectively, I can't account for the remaining outputs (536, 756, and 816 nm). Can someone kindly shed some light on what processes are likely involved here?. Please see the attached file for the experimental set up and output spectra at two different temperatures.
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@ Valeriy. Evgenjevitch. Ogluzdin , Thank you for your suggestion.
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Frequently in nonlinear optics, to study the dynamics of short optical pulses of femto-second duration one use to adopt multi scale method and derive nonlinear Schrodinger/Gingburg-Landau equation. In many cases, the final equation is obtained keeping terms up to third-order, whereas other cases it is obtained after fourth-order. How to estimate accuracy in both cases?
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A useful material is as below:
J. R. Taylor (ed), “Optical Solitons – Theory and Experiment”, Cambridge University Press, Cambridge, UK (1992).
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More explicitely:
If I have a pump laser of a given wavelength and I feed it as a pump into a fiber, does the output contain the pump laser wavelength (minus converted power fraction) and the fiber laser's wavelength at a different wavelength with a fixed phase relationship (not necessarily known).
Or in other words, if I had a nonlinear crystal based optical setup and would not depend on frequency doubling, but only frequency conversion, could I replace the nonlinear crystal by a (laser) fiber?
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You have posed a very interesting query. Going by your words, the two situations are totally different. If you look minutely, the interchange is not recommendable. However, for your own analysis, you can proceed and compare the results. As I can see, you are more interested in getting variations in frequencies. When the question of replacement comes, you can not rule out the coherence length. In case of fiber lasers, it is different from that of non-linear crystal. Another point is that modulator dimension (NL crystal and fiber ) will also have an impact on the out put. Anyways, best wishes for your endeavor and I will be glad to see them.
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I'm preparing a spatially-resolved oblique diffuse reflectance experiment with the objective of finding the reduced scattering (mu_s') and absorption (mu_a) coefficients of some turbid samples.
My setup is very similar to that described in Hu et al 2017 (DOI 10.1007/s11694-017-9465-x). I have a couple of technical/practical questions related to this experiment, so if you have never done something alike, you might want to skip this one.
I use an optical fiber to deliver the light at a 45 degree angle at the surface of the sample (liquid) and I'm collecting the reflectance with another fiber that moves in a parallel plane to the incidence plane. This is necessary to avoid collisions between the fibers. The liquid and the fibers are separated by a 0.2 mm cover glass.
The two planes are 2.2 mm apart from one another (delta_y). The main paper describing the theory behind this experimental setup is Lin et al 1997 but the authors (as well as other authors that do similar stuff) do not explain how the shift between incidence and collection planes should be handled in terms of modelling. To me it makes sense that this delta_y enters in the definition of the distances (rho_1 and rho_2) used to compute the theoretical reflectance (R), obtained from the diffusion approximation. However, when I plug in all the values into my code to find \mu_eff by fitting my data, I cannot find a stable solution. I have to "artificially" increase delta_y in order to get \mu_eff values near the expected/theoretical ones. Has anyone experienced such problems?
I've tried small adjustments to delta_x (due to possible errors in the light entry point measurement) and different optical coupling parameters (A), but nothing seems to works. Could it be related with the width of the light beam that enters the sample? In my case the projected beam spot in the surface of the turbid sample is an ellipse of 2.1 x 1.4 mm.
If you have any comment/idea about possible sources of error that I'm might be overlooking, please leave a comment. Also I would like to know your suggestions about the best way to normalize the data before doing the fit procedure for this kind of experiment.
I appreciate any help, advice, reference or person contact that could help me move forward with this. Thanks.
Dário Passos
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Dear Eugene and Furkan
thank you for your comments. Regarding my problem, I know that I've done everything by the book into accounting for the delta_y displacement in the geometry of my oblique diffuse reflectance experiment. What I find strange is that almost no one tells how they handle this displacement in their works. I've mails 4 different authors (some with recent publications) and no one replied back... I find that odd. Or they didn't care about the effect or then they didn't thought about it (which I doubt). Nonetheless I would like to hear from someone that had applied this same kind of experiment to find about tips on how to optimize it.
In principle, and according to the literature, the diffuse approximation should be enough to explain the light behaviour in the kind of turbid samples that I'm probing (biological tissues, milk, etc) so no need to go into specific models. However, I admit that some of samples might not be well explained by assuming isotropic scattering as the diffusion approximations relies on. Some food for thought for sure.
Cheers and thanks
Dário
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Hi,
I am attempting to simulate in comsol a nonlinear metamaterial (which by using effective media theory I can approximate as a periodic slab of artificial material).
My process is as follows:
Run a frequency domain study, this contains my model, a propagating wave (from the emw port). I perform the comsol study and place domain point probes at points of interest. I monitor the Ex, Ey, Ez, and normE here.
Next, I find the voltage at a point in my material (at split of my split ring resonator) simply by multiplying a component of the E field at this point by the gap size of the split in the ring.
Next, I couple a time domain study of my model to a circuit model so I can apply a voltage source. I am looking for the second harmonic so I apply V(2w) =1/2 a(Vw)^2 voltage (from an expansion of the voltage in the linear model with 'a' being a nonlinear co-efficient which I will know).
Following this, I have a scattered boundary condition as a source of the field I have saved from my emw.Ey etc run from the frequency domain and I use a polarisation term to couple the incident field chi(2) *(emw.Ey)^2, where chi has been found via an equivalent circuit analysis.
I then export my time domain results to matlab (just for sake of ease as I'm more familiar with matlab) and take the abs(fft(Efield)) to find the frequency content of the output from my model.
I'm aware this method is probably incorrect, but any pointers, or corrections from correct comsol usage to correct method to simulate nonlinear materials, would be greatly appreciated.
Thank you very much
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I am looking for a simple and inexpensive method to compress my Nd:YAG nanosecond pulse laser into hundreds picosecond pulse. Please suggest me some if you know or have experience on this pulse compression issue. Thanks!
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SBS compression can realize this goal. you can see the literature of zhiwei lv or hongjin kong.
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I'm looking for the source giving quantatively numbers for o- and e-rays refraction indexes in the ice crystal depending on the wavelength.
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Well, it is good to hear from you again, Aleksey! :-) It sounds as though you have done an interesting experiment that relates to the work published in 1957 by R.C. Emmons and R.M. Gates, which you can find at https://tinyurl.com/yd932t29 .
My own work explores the viability of abandoning the instruction "In the determination of the refractive indices of mineral grains by the immersion method, the grains must be in the extinction position, under which condition alone does the transmitted light have the value of one refractive index". Instead, I bring what I call a "fragment" (part of a crushed grain) to NO PARTICULAR ORIENTATION, before comparing its RI to that of the immersion liquid.
One of my primary goals has been ?simply? to discover whether statistically-significant data sets can be created from data derived by assessing whether each fragment encountered during a count is of Lesser, is Equal to, or is Greater than the RI of the immersion liquid (previously calibrated over the visible spectrum and the temperature range of the experiment: about 23°C to 60°C). Results confirm a success in creating statistically-significant data sets, but it is not so easy to say exactly what details are due to displays by any particular mineral/mineraloid/glass phase.
Nonetheless, in 2017 I took first place in the "Data Art" category of this https://www.lpl.arizona.edu/art/ contest, the winning image being available at https://tinyurl.com/yd994zpl . I did not place this year, with any of these https://tinyurl.com/y8h2w3ts entries. "Can't win 'em all." ;-)
In case you do not have it already, by standing permission of GSA I point you to a copy of R.C. Emmons's 1943 Chapter 5, GSA Memoir 8, "Double Variation Procedure for Refractive Index Determination": https://tinyurl.com/yabku63f . A copy of my dissertation can be found (at least for now) at https://tinyurl.com/y9bkao6n .
Work -- more recent than what I entered this year into the abovementioned art exhibition and contest -- has forced me again to seek a way to plot in 4D, after the plans I had to try to do that in 1994, as depicted at https://tinyurl.com/yaxrnzmv . Might you be able to help me with that graphics programming or know somebody who can?
I hope this response is helpful.
Sincerely, -Steve-
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It is known that graphene and graphene oxide liquid dispersion
(in DMF/NMP) show third order non linear behaviour such as Spatial Self-Phase Modulation (SSPM). Far field diffraction ring pattern due to SSPM is observed even when one attempts to perform z-scan (both with CW and pulsed laser). While open aperture measurement doesn't offer much complication as I only have to focus the transmitted beam onto the detector, I am not very sure how to overcome the ring structure while performing closed aperture z-scan.
Of course, drop casted /spin coated samples don't show SSPM feature, but I am curious about liquid dispersion only.
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For closed aperture Z-scan measurements, one needs to avoid nonlinear absorption and hence the measurements are always performed at low input peak power/intensity. This is the thumb rule.
Even for nonlinear absorption there can be intensity dependent processes (SA at first turning to RSA at higher peak intensities). It depends on the sample and excitation wavelength along with peak intensities used.
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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.?
Thanks
Surya
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In addition to the previous comments, bearing in mind the length of the fiber links and the environmental factors, for fine tuning you can use commercially available devices.
See in the link:
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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.
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Following.
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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.
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When the nonlinear response is dominated by the Kerr effect (nonlinear refractive index change) the asymmetry is easy to understand in the limit of thin media. Essentially the Kerr effect induces a "nonlinear lens" in the material which changes the subsequent propagation of the beam. The example you show in your question would correspond to the case of a negative Kerr effect (n2<0). When the sample is placed before the focal plane of the physical lens, the combined effect of the lens originally used to focus the beam and the negative focal length "lens" induced in the sample is to translate the beam's focal plane further along the z-axis. Thus by the time the beam reaches the aperture it has not diverged as much and the transmission through the aperture is higher. Conversely when the sample is placed behind the focal plane of the physical lens, the induced negative lens leads to an increased divergence and consequently a lower transmission at the aperture. It is not just the phase shift, but difference in curvature of the wavefronts on either side of the focus that gives rise tot he assymmetry. You can find a more detailed explanation in the book "Fundamentals of Nonlinear Optics" by Powers and Haus, chapter 8.
Basically the optics is roughly the same as in the thermal lens case. The main difference is that for an electronic nonlinearity in the absence of absorption, the induced lens is an "instantaneous" response to the transverse profile of the incident beam, whereas in the thermal case it is the radial variation of the adsorbed energy convoluted with thermal diffusion that produced the effective lens induced by the incident beam. Of course the detailed shape of the Z-scan curve will be different, due to the difference in the transverse variation of the induced refractive index change in the two cases. In the "instantaneous" electronic case, this variation will follow the radial variation of the incident beam, in the thermal case the balance between the power deposited by the incident beam and diffusion of the heat within the sample will determine the spatial profile of the induced refractive index change.
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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.
[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.
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I think when nonlinear refraction is dominant, you can extract the nonlinear parameters from the closed z-scan with some confidence. However, there are cases , for example when either NL refraction or absorption are dominant, that you cannot do that without ambiguity, so that is why it is customary to run the open z-scan to get the NL absorption parameters first, and then used them in the closed-aperture results. Experimentally all you need is a beam splitter in the far field, and an extra detector yo obtain both the open and closed-zscan traces at the same time
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Measuring TPA coefficient (two photon cross section) and non-linear optical refractive index using Z-scan method with pulse or CW lasers is routine. So, is two photon excited PDT by CW laser achievable?
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Measuring TPA coefficient (two photon cross section) and non-linear optical refractive index for vacuum is not possible. Only protons - nuclons of medium (and electrons ) are substantial for this routine.
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What is the benefits to study the nonlinear properties of fiber optics ?
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Right! Leonardo.
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In Non-linear optical activity what does negative polarizability of an isolated molecule indicate (through gaussian calculation)?
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Interesting question. I think you have to consider that the hyperpolarizabilities that give rise to the nonlinear response, are deviations from the linear behaviour. So, a negative hyperpolarizability for one molecule simply implies that the induced dipole moment at a given light irradiance is smaller than it would be if only the linear term would be kept.
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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.
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I really appreciate your help with my project, Prof.Zbigniew Motyka and Prof.Maria Chiara Ubaldi.
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For Nonlinear optical phenomena and materials that are used in the field of nonlinear optical
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Dear Dr. Ali Benghia
I suggest you book Physics of Nonlinear Optics, Guangsheng He, Song H. Liu-World Scientific
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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.
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Thank you very much, Dr. Reza Taheri Ghahrizjani
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I want to create a zero-order Bessel beam. But I am a little bit confused how will I  create zero-order?. As far I know the most simple way to create a Bassel beam is with an Axicon lens. So my queries are below-
1. Can I use axicon lens to create zero-order Bessel beam?
2. Does apex angle of the axicon lens play a critical role to create zero-order Bessel beam?
3. Is there any other way to create zero-order Bessel beam?
Please help me. Thank you in advance.
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Dear Dr.Subir Das,
I have studied Efficiency of the second-harmonic generation with the zeroth-order bessel-profile beams in uniaxial crystalsand and I have also learned how to create the zero order Bessel beam. To create the zero order Bessel beam we can use annular slit as in the work of Prof.D. MCGLOIN * and Prof. K. DHOLAKIA.
However, the most convenient method is probably to use an axicon.