- This topic has 3 replies, 2 voices, and was last updated 5 years, 8 months ago by
Scott Newman.
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March 13, 2019 at 7:32 am #50742
Michael Kowalczyk
Participanthello, does anybody know how to define material so that I can specify scattering and absorption coefficients, I’d like to simulate light propagation in biological tissues which are highly scattering medium, thank you
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March 14, 2019 at 1:27 pm #50814
Scott NewmanModeratorHi Michael,
OptiFDTD can model material absorption through complex refractive indices. Scatting is done simply from the geometry of the particles in the material. However, I believe you are referring to the coefficients that are based off of scattering/absorption cross-sections which is not an input into the simulation engine as it would need the direct material properties (macro versus micro). Is my assessment of what you are looking for correct? Could you provide more details or an example of what you are looking for.
You could use the product to determine the absorption and scattering coefficients.
Scott
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March 14, 2019 at 2:06 pm #50817Participant
Hi Scott
Yes, you’re right, I’m trying to analyze scattering and absorption of laser light at wavelength of 810nm from single cell with nucleus (microscale= 10 microns) but in the end, I’d like to observe scattering and absorption of laser light as it propagates through the tissue (several centimeters in depth). Obviously, it’s too much calculation to make a tissue as the assembly of millions of cells.
You mention that it’s possible to derive macroscopic scattering and absorption coefficients from single cell simulation (linking micro with macro scale), would you be so kind as to guide me through this process please?
Best Wishes
Michael
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March 18, 2019 at 9:31 am #50845Scott NewmanModerator
Hi Michael,
Perhaps micro/macro was not the best way to describe it. What FDTD can do is model the bulk properties of a material through the complex refractive index (n_complex = n – jk). If you can model your material in this fashion then OptiFDTD can do so. This would of course only model the absorption. Scattering is from the micro structure which you are correct would be difficult to directly model.
The other concern I have is that you are looking to model structures centimeter in scale. A finite-difference time-domain solution requires a resolution with a maximum size of roughly lambda/10 (often much smaller) for numerical stability. This could lead to a very computationally intensive calculation. What wavelength are you operating at?
Scott
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