If I’m not mistaking , this only works for dispersive media of which the real part is positive, because for negative epsilon you just get exponential decay There is way to verify your material: http://www.mail-archive.com/[email protected]/msg03527.html
Best regards, Milan From: [email protected] [mailto:[email protected]] On Behalf Of ??? Sent: dinsdag 2 november 2010 15:08 To: [email protected] Subject: [Meep-discuss] Verification of material (Au) dispersion Dear MEEP users, I get a Drude model for Au (the model itself has been proved to be accurate with applicable wavelength range: 500~1000nm), and want to verify it through simulaltion as the MEEP Tutorial of Material dispersion. I made a slight change to the given tutorial .ctl file. However, the result achieved is not what I have expected. The .ctl command and partial simulation results are as follows. Any statement about my problem will be highly appreciated. With best regards. *************************************** The ctl command: ; Define lengthscale a = 200nm ; Wavelength range : 500~1000nm ; Corresponding frequency range in MEEP : 0.2 ~ 0.4 (set! geometry-lattice (make lattice (size no-size no-size no-size))) (set-param! resolution 20) (set! default-material (make dielectric (epsilon 5.9673) (E-polarizations (make polarizability (omega 0.666667e-10) (gamma 0.0106133) (sigma 4.4673e20)) (make polarizability (omega 0.43338) (gamma 0.0699067) (sigma 1.09)) ) ) ) (define-param fcen 0.3) (define-param df 0.2) (set! sources (list (make source (src (make gaussian-src (frequency fcen) (fwidth df))) (component Ez) (center 0 0 0)))) (define-param kmin 0.2) (define-param kmax 0.4) ; I am not sure if the values for kmin and kmax are right. However, even if I change these values, the results and the problem are the same. (define-param k-interp 99) (define kpts (interpolate k-interp (list (vector3 kmin) (vector3 kmax)))) (define all-freqs (run-k-points 200 kpts)) ; a list of lists of frequencies (map (lambda (kx fs) (map (lambda (f) (print "eps:, " (real-part f) ", " (imag-part f) ", " (sqr (/ kx f)) "\n")) fs ) ) (map vector3-x kpts) all-freqs ) ********************************* Partial simulation results: ... harminv0:, frequency, imag. freq., Q, |amp|, amplitude, error run 0 finished at t = 250.0 (10000 timesteps) freqs:, 1, 0.2, 0, 0 freqs-im:, 1, 0.2, 0, 0 harminv1:, frequency, imag. freq., Q, |amp|, amplitude, error run 1 finished at t = 250.0 (10000 timesteps) freqs:, 2, 0.202, 0, 0 freqs-im:, 2, 0.202, 0, 0 ...
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