I am simulating strip waveguide Bragg grating for various corrugation width. i could not correlate the simulation results (EME analysis result)
a) neff is effective index without grating. this formula has nothing to do with corrugation width. but plots show that Bragg wavelength shifts teft with increase in corrugation width.
b). according to this formula bandwidth should be increased with increase in corrugation width (wider the corrugation width higher is the coupling coefficient), but in plots BW is lower at Δw = 80 nm than Δw = 60 nm than Δw = 40 nm.
formula ref: Wang, X. (2013). Silicon photonic waveguide Bragg gratings (T). University of British Columbia. Retrieved from https://open.library.ubc.ca/cIRcle/collections/24/items/1.0165738 (Original work published 2013)
EME code is here UBG_EME.lsf (4.7 KB)
how does ‘EME-analysis’ calculate s-matrix? does it use TMM; first calculate low and high effective index by FDE, then using fresnel equation calculate constituent matrices and multiply in reverse order?
(as TMM explain in book Chrostowski, Lukas, and Michael Hochberg. Silicon photonics design).