Let me start by saying that Optics is not my field but I am very interested in it. What I am trying to do is to find a way to numerically simulate propagation of light in a GRIN media. Is there any easy to use code? or a guide?
Thanks in advance for your help,
Nasseh
Hi
Can I assume your problem is paraxial and that backreflections are negligible ?
If so, it's extremely easy to simulate using Beam Propagation Methods (BPM). If this is the case, I can provide some references\code.
Hi Hanan
Thanks for your answer. Yes paraxial can be assumed but I am not sure what you mean by back reflections. I appreciate any help greatly.
Nasseh,
If you are not going to do anything fancy with a GRIN media I suggest to make yourself an analysis using the ABCD matrix method. It will be easy and will give you a better understanding of the physics behind. You can read a great introduction about it in "Modern Optics", R.D. Guenther chap. 5.
http://www.amazon.com/Modern-Optics-B-D-Guenther/dp/0471605387
Hanan was right when asking about back-reflections or retro-reflections. The thing is that if the gradient is sufficiently steep, you get a strong back-reflection, and this is the major effect to worry about when dealing with those media. And it is tough to calculate unless you are looking at the simplest, 1D-propagation (plane wave). Only in the case of really slow varying in space refractive index, the calcs are easy (and there is a small retro-reflection); to have an analytic insights one can use a WKB approximation (see e. g. the paper below). However, even in this case, there could be some interesting effects like a "gradient marker" wave:
http://psi.ece.jhu.edu/~kaplan/PUBL/AEK.pubs/131.pdf
In the same paper you will find a description of "inverse scattering" method of numeric calculations that allows one to calculate the wave propagation in general case that includes back-reflection at an arbitrary-steep gradient (see e, g. discussion following Eq. (6)).
I second what alexander said.
If you want a good intro, look here (lec 16) : http://emlab.utep.edu/ee5390cem.htm
Thanks for all of the answers. Hanan the link is fantastic. Alexander I am going to read the paper you sent. Thanks for your answer. Felip Thanks. I will try to find that book.
Refracting index gradient should be defined first, for example:
Radial: similar to graded index or step index optical fibers.
Axial: Periodical, just similar to FBG or 1D photonic crystals.
Axial: Drastic in boundary, similar to Fresnel reflection.
Famous numerical codes such as Zimax or Glad may be helpful based on ABCD matrix or ray tracing concept.
You can also use simulation software like COMSOL, OptiWave , etc if you like to do a CAD approach. Else, Matlab and the codes mentioned earlier would work perfectly...
FDTD software are very powerful and should be able to handle your cases. Commercial FDTD software such as OptiFDTD and FDTD solutions are very easy to use but a little expensive. You can apply for trial versions though and they work the same way as the real product. If you are into coding, you can also try MEEP, it is free and also very powerful. It is not very user-friendly as compared with commercial FDTD software.
Yeah I am on a budget in this project. I should find a less expensive way to this simulation.
This is hard to calculate and there are various software for its simulation. Zmax ,Oslo and Comsol softwares provide suitable way to determining lightpath in such media. you can calculate and optimize your parameters with them. The first two are optical software so you can design your optical system easily with them. Comsol is more physical more difficult simulation software and you should have good dominance on your problem.
It seems that MATLAB code will be the best to use ABCD matrix. Alternately you can use Scilab from http://www.scilab.org/ which is open source and you will not need to worry about funding. Please donot forget to mention the same in your publication.
You can try to use our FDTD library for C++. It is open source. You can find the documentation and downloads on the www.fdtd.kintechlab.com.
But what is the size of your sample and the scale of refractive index change? I mean the order of it. If it is much larger than the wavelength you can try some ray tracing technique. If sizes are about the waveength, in this case FDTD will be better.
A free download - useful software from internet is Rsoft which includes FDTD as a solver of Maxwell 's eqs. It is adquate to fulfill your case.
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