Hi Paolo, Your simulation looks similar to the technique used for calculating the emission enhancement of an emitter inside a cavity (see: Hwang, Phys. Rev. B, vol 60, 1999 ). I’m not sure what the desired result of your experiment is. If it is to get the resonant frequency and Q-factor…use harminv. If you want the total spectrum, monitor the field on a grid point and do an FFT afterwards.
Best regards, Milan Marell From: [email protected] [mailto:[email protected]] On Behalf Of paolo bettotti Sent: maandag 17 januari 2011 16:58 To: [email protected] Subject: Re: [Meep-discuss] normalization Dear users, I am sorry for the previous, incompleted mail. I am trying to simulate an L3 cavity. My question is related to how normalize the spectrum. I am designing only the PC cavity (no in/out WG). Initially I designed a flux region on one side of the simulation cell. But I found that max transmission was always greater than 1 (if normalized to respect an empty simulation domain). Thus I put two monitors orthogonal to each others ('cause I though that the diffraction could play a major role) but I get the same. I found that even a test structure like the one below, gives me a transmission maximum 20% greater than the one of the normalization run. ________________ | | | | | | | 0 | | 0 0 | | 0 0 | | 0 | | | | | |_______________| This difference does not depends on resolution or simulation duration or pulse width. It is probably a quite stupid thing but I cannot understand where I am wrong... Below there's my ctl code for the test structure: (define-param diel_hole 1);dielectric constant of the holes (define-param diel_slab 2.56);dielectric constant of the bulk (define-param res 10);resolution pixels per unit of distance (define-param rad 0.3);radius of the holes (define-param numlayers 22);number of layers (define-param dpml 2) (define-param freq 0.4397) (define-param defreq 0.01) (define-param nfreq 1000) (define-param fcen_h freq);for harminv - bandgap for h=0.5 r=0.3 triangular hole struct. is between ~0.27 and 0.35 (Chap 4) (define-param df_h defreq);for harminv (define-param sx 32); x-size of the cell (define-param sy sx); y-size of the cell (define-param runtime 1000) (define-param sourcex 0);0.137);x coord of the point source (define-param sourcey 0);-0.09);y coord of the point source ;(set! symmetries (list ;(make mirror-sym (direction Y) (phase 1)) ;(make mirror-sym (direction X) (phase -1)) ;)) (define eps-averaging? true) (set! pml-layers (list (make pml (thickness dpml)))) (set! resolution res) (set! default-material (make dielectric (epsilon diel_slab)));default material: high dielectric (set! geometry-lattice (make lattice (size sx sy no-size)));lattice sx*sy*sz (set! geometry (list ; (make cylinder (center 0 2)(radius (* 1 rad))(height infinity)(material (make dielectric (epsilon diel_hole)))) ; (make cylinder (center 0 -2)(radius (* 1 rad))(height infinity)(material (make dielectric (epsilon diel_hole)))) ; (make cylinder (center (/ (sqrt 3) 2.0) 0.5)(radius rad)(height infinity)(material (make dielectric (epsilon diel_hole)))) ; (make cylinder (center (/ (sqrt 3) -2.0) 0.5)(radius rad)(height infinity)(material (make dielectric (epsilon diel_hole)))) ; (make cylinder (center (/ (sqrt 3) 2.0) -0.5)(radius rad)(height infinity)(material (make dielectric (epsilon diel_hole)))) ; (make cylinder (center (/ (sqrt 3) -2.0) -0.5)(radius rad)(height infinity)(material (make dielectric (epsilon diel_hole)))) ; (make block (center sourcex sourcey) (size 0.5 2) (material (make dielectric (epsilon diel_hole))));source ; (make block (center (- (/ sx 2) dpml 2) 0) (size 0.5 (- sy dpml dpml 1))(material (make dielectric (epsilon diel_hole)))); monitor ; (make block (center (/ sx 2) 0) (size (* 2 dpml) sy)(material (make dielectric (epsilon diel_hole)))); dpml ; (make block (center (/ sx -2) 0) (size (* 2 dpml) sy)(material (make dielectric (epsilon diel_hole)))); dpml ; (make block (center 0 (/ sy 2)) (size sx (* 2 dpml))(material (make dielectric (epsilon diel_hole)))); dpml ; (make block (center 0 (/ sy -2)) (size sx (* 2 dpml))(material (make dielectric (epsilon diel_hole)))); dpml (make block (center 0 0) (size sx sy)(material (make dielectric (epsilon diel_slab)))); for normalization )) (set! sources (list (make source (src (make gaussian-src (frequency freq)(fwidth defreq))) (component Ex) (center sourcex sourcey) (size 0 0))));off-center delta point source to excite all modes (define trans ; transmitted flux (add-flux freq defreq nfreq (make flux-region (center (- (/ sx 2) dpml 2) 0) (size 0 (- sy dpml dpml))))) (define trans2 ; transmitted flux (add-flux freq defreq nfreq (make flux-region (center 0 (- (/ sy 2) dpml 2)) (size (- sx dpml dpml) 0)))) (run-sources+ runtime (at-beginning output-epsilon) ; (at-every 100 output-efield-x) ) (display-fluxes trans trans2)
_______________________________________________ meep-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
