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.
Research is a universal/global construction or practice. Proposal format is generally the same irrespective of discipline, as seen in Pal's suggestions above.
Hello,
you are right. The media with high nonlinear refraction index can’t change the power of laser beam by itself. But in combination with aperture in far field (after the sample with high nonlinear refraction index) we get the optical limiter which is based on the nonlinear refraction effect. So in case of nonlinear refraction we don’t consider the nonlinear media by itself. We does it only in combination with aperture.
As an addition to the references from prof. Dibakar Pal I can recommend this articles
http://www.phys.unm.edu/msbahae/publications/z-scan.pdf
https://www.researchgate.net/profile/Eric_Van_Stryland/publication/237365066_High-sensitivity_single-beam_N2_measurements/links/0c96053b966ef9dc07000000/High-sensitivity-single-beam-N2-measurements.pdf
http://www.sciencedirect.com/science/article/pii/S0030399204002439
Article High-sensitivity single-beam N2 measurements
Hi,
I think nonlinear refraction is one of energy-spreading types of optical
limiting as described in article below..
http://shodhganga.inflibnet.ac.in/bitstream/10603/9919/11/11_chapter%206.pdf
Dear Dr.Igor Yanusik,
Thank you for your comment. But nonlinear refraction only result in energy-spreading of laser beam and don't change power of laser beam. So, we can not detect optical limiting effect when measuring output power versus input power.
Thank you very much, Prof.Leonid Koldunov and Prof.Matthew Iwuchukwu
Dear Professors,
I still do not understand why Two-photon absorption causes optical limiting effect:
http://aip.scitation.org/doi/abs/10.1063/1.2734904
Hi Lam,
I had some experience with optical limiting (OL), and my comments about your question are: (i) nonlinear index (NI) could have important effect for OL if the material/structures have resonant features (micro-cavities, photonics crystal etc.) so that intensity at resonant mode(s) or wavelengths is changed with RI. Good design could make OL based on that. (ii) in general cases, OL effects are mostly from nonlinear absorption (NA) (saturable absorption, two photon absorption etc.). Note that, many optical nonlinear materials have both NA and NI.
Hope that would help. By the way, I will visit HCM city on December, if you have time we can meet there.
Best,
Dan
Dear Nguyễn
the following paper is helpful:
Article A review of optical limiting mechanisms and devices using or...
There are many approaches limit the optical power. Mostly, absorptive processes such as saturable absorption (or nonlinear absorption in general). However, there are ways to utilize the nonlinear refraction to limit the light transmitting through the medium. Diffractive nonlinear materials can be a simple example, where large nonlinear refraction causes changes in refractive processes or increases the Fresnel coefficient and as a result material won't be able to transmit the light.
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