Re: [Meep-discuss] Resolution dependence silver nanosphere
I agree with Gursoy, your resolution appears to be too low. His rule of thumb of a minimum of 8 (I actually prefer 10 - 20) pixels or grid points for one wavelength is good for wave propagation in lossless dielectrics. Lossy materials, like real metals typically need much higher resolution. My rule of thumb is that you need a minimum of 1 or 2 grid points per skin depth of your lossy material. You can calculate skin depth from the n and k (real and imaginary parts of refractive index) of silver around your wavelength of interest. Another piece of advice that has been expressed many times in this mailing list is to run several simulations each with increased resolution until you get two successive results that do not change much. Good luck, Neal On Thu, May 30, 2013 at 2:23 AM, gursoy akguc akgu...@yahoo.com wrote: I think your resolution is way low for this system. as far as I can see your geometry is 700nm cube res 32 means your pixel cell size is about 22nm. source is 363nm and in the dielectric material you use 8 it means wavelength is about 45nm. rule of thumb is 1 wavelength needs to be represented by 8 pixels, but your 8 pixels makes 176nm about 4 times higher than wavelength. my suggestion is to use 120resolution minimum to see some meaningful result comparable to Mie. Gursoy B. Akguc *From:* niels jelsma c.j.m.jel...@student.rug.nl *To:* meep-discuss@ab-initio.mit.edu *Sent:* Wednesday, May 29, 2013 2:23 PM *Subject:* [Meep-discuss] Resolution dependence silver nanosphere Dear All, I'm trying to calculate the dipolemoment of a silver nanosphere in Meep. In the end I am interested in looking at a chain of spheres and the transmittance, p_last / p_first. However for just a single sphere I don't understand what values I have to choose for the resolution to get proper results. I've read on the mailing list that I should choose a resolution that gives at least 8pixels/wavelength and then double the resolution to get better results. However, increasing the resolution this way sometimes gives me worse results. A simplified version of my script can be found here: https://gist.github.com/maxnuf/5669273 I've setup a sphere with radius 25nm in 3d space and a continuous source as plane-wave. After running it for a while to get into a steady-state I integrate the Polarization in a volume containing the sphere to find the dipolemoment. I expect to find a peak near the resonant frequency. So I run the simulation for several input source wavelengths. However, for different resolutions, I get completely different results. I don't know what to do to remedy my problem. As can be seen in this figure: http://postimg.org/image/kua54kwq9/ At a resolution 32 I see a sort of dip where I expect the resonant frequency (which should be at 363nm according to Mie theory) I'm using Meep 1.2 and a Drude-model for my silver sphere. How can I determine which resolutions are suitable? Thanks, Niels ___ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss ___ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss ___ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
[Meep-discuss] Problem with the simulation of an opal
Hi everybody, I'm fairly new to meep and have a problem with the simulation of an opal structure. By searching in google I found a discussion from 2006 about a code for multilayer opals in which a code was posted that worked for a simple opal. Still I get transmissions larger that one. Anyone here with an idea why that happens? Here is the code: ; transmittance/reflectance of a fcc structure a=1. (set! eps-averaging? false); No epsilon averaging ;---EXTERNAL PARAMETERS--- (define-param r_sph 0.36); Oxide spheres radius (define-param r_max (/ 1 (sqrt 6))); Thickness of the Si layer grown inside the opal (define-param nl 3) ; number of periods = (3 layers each) (define-param pmlt 2) ; thickness of the pml (define-param pad 3); distance between source and sample (define-param no-phc 1) ; if true (1), have air, false (0), PhC ;--CELL DIMENSIONS- (define unitcell (sqrt 3)) ; size of the unitcell in Z (define distz (/ 1 (sqrt 3))); distance between single layers (define sx (/ 1 (sqrt 2))) ; size of cell in X direction (define sy (sqrt 1.5)) ; size of cell in Y direction (define sz (+ (* 2 pad) (* 2 pmlt) (round (+ 0.5 (* nl unitcell) ; size of cell in Z direction (set! geometry-lattice (make lattice (size sx sy sz))) ;--USEFUL VALUES (define sx_half (/ sx 2)); (1/sqrt(8)) (define sy_half (/ sy 2)); (sqrt(3)/sqrt(8)) (define sy_sixth (/ sy 6)); (1/sqrt(3x8)) (define nsx_half (/ sx -2)); -(1/sqrt(8)) (define nsy_half (/ sy -2)); -(sqrt(3)/sqrt(8)) (define nsy_sixth (/ sy -6)); -(1/sqrt(3x8)) (define cell_center (* unitcell (+ 0.5 (* -0.5 nl; z-coordinate of the first unit cell (define bottom_sample (+ (* unitcell (- nl 1)) cell_center distz (/ 1 (sqrt 8 ; Z coordinate bottom of spheres (define substrate_centerZ (+ (/ sz 4) (/ bottom_sample 2))) (define substrate_sizeZ (- (/ sz 2) bottom_sample)) ;MATERIALS--- (define silica (make dielectric (epsilon (* 1.45 1.45 (define silicon (make dielectric (epsilon (* 3.5 3.5 ;--GEOMETRY- (set! geometry (if (= no-phc 1) (list (make sphere (center 0 0 0) (radius r_sph) (material air)) (make block (center 0 0 substrate_centerZ) (material silicon) (size sx sy substrate_sizeZ)) ; substrate ) (append ;OPAL OF Si SPHERES (geometric-objects-duplicates (vector3 0 0 unitcell) 0 (- nl 1) (list ;Layer A - thin Si (make sphere (center nsx_half nsy_sixth (- cell_center distz)) (radius r_max) (material silicon)) (make sphere (center sx_half nsy_sixth (- cell_center distz)) (radius r_max) (material silicon)) (make sphere (center 0 (+ nsy_sixth nsy_half) (- cell_center distz)) (radius r_max) (material silicon)) (make sphere (center 0 (* 2 sy_sixth) (- cell_center distz)) (radius r_max) (material silicon)) ;Layer B - thin Si (make sphere (center nsx_half sy_half cell_center) (radius r_max) (material silicon)) (make sphere (center nsx_half nsy_half cell_center) (radius r_max) (material silicon)) (make sphere (center sx_half sy_half cell_center) (radius r_max) (material silica)) (make sphere (center sx_half nsy_half cell_center) (radius r_max) (material silicon)) (make sphere (center 0 0 cell_center) (radius r_max) (material silicon)) ;Layer C - thin Si (make sphere (center nsx_half sy_sixth (+ cell_center distz)) (radius r_max) (material silicon)) (make sphere (center sx_half sy_sixth (+ cell_center distz)) (radius r_max) (material silicon)) (make sphere (center 0 (+ sy_sixth sy_half) (+ cell_center distz)) (radius r_max) (material silicon)) (make sphere (center 0 (* 2 nsy_sixth) (+ cell_center distz)) (radius r_max) (material silicon)) )) ;OPAL OF OXIDE SPHERES (geometric-objects-duplicates (vector3 0 0 unitcell) 0 (- nl 1) (list ;Layer A - oxide (make sphere (center nsx_half nsy_sixth (- cell_center distz)) (radius r_sph) (material silica)) (make sphere (center sx_half nsy_sixth (- cell_center distz)) (radius r_sph) (material silica)) (make sphere (center 0 (+ nsy_sixth nsy_half) (- cell_center distz)) (radius r_sph) (material silica)) (make sphere (center 0 (* 2 sy_sixth) (- cell_center distz))
[Meep-discuss] Photonic Crystal Fiber
Hi everyone :) can somebody help me with the codes of Solid Core Photonics Crystal Fiber? ive need it to calculate the transmission spectra.. really need it.. thanks in advance___ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
