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Fitting the complex refractive index of a material over a broad
bandwidth to a sum of Drude-Lorentzian susceptibility terms requires
some trial and error, as explained in a previous post, and another. As an example, here are the fitting parameters for crystalline silicon for the interval 450-650nm based on values provided in M. Green, Solar Energy Materials and Solar Cells 92, 1305 (2008). A comparison of the reference and the fitting data are shown for the real and imaginary parts of the permittivity. ; 'a' is the unit length of the simulation in nanometers (define cSi-eps-inf 8.15) (define cSi-frq (* 2.7098e-03 a)) (define cSi-gam (* 6.1394e-05 a)) (define cSi-sig (/ (* 3.3948e-05 (sqr a)) (sqr cSi-frq))) (define cSi (make medium (epsilon cSi-eps-inf) (E-polarizations (make lorentzian-susceptibility (frequency cSi-frq) (gamma cSi-gam) (sigma cSi-sig))))) |
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