Dear Steven, MPB users,
Is it possible to produce the band structure of higher order guided modes
in a PhC slab with MPB?
This is mostly a problem for guides with high index contrast cladding/core.
The example below shows the parameters used by Ryu et al in J. Appl. Phy 88 p4941 for an air-bridge PhC. This produces the band diagram for TE-like modes but only for the fundamental guided mode. The first order guided mode shown in the paper does not appear here. My understanding from the manual is that (run-zeven) select solutions which are symmetric (even) with respect to the plane bisecting the slab (z-parity = 1 here) hence the reason why this antisymmetric mode can not be selected this way. However, (run-zodd) does not work neither since this considers "TM-polarised" modes, unless my interpretation of even and odd is wrong here. Is there another integrated function we could use instead or does this require extra calculations performed outside MPB (such as effective index...)?
(define-param h 0.4) ; thickness of the slab
(define-param GaAs 11.56)
(define-param r 0.4)
(define-param supercell-h 4)
(define k-interp 8)
(set! mesh-size 6)
; triangular lattice
(set! geometry-lattice (make lattice (size 1 1 supercell-h)
(basis1 (/ (sqrt 3) 2) 0.5)
(basis2 (/ (sqrt 3) 2) -0.5)))
(set! geometry
(list (make block (material air)
(center 0)
(size infinity infinity supercell-h))
(make block (material (make dielectric (epsilon GaAs)))
(center 0) (size infinity infinity h))
(make cylinder (material air)
(center 0) (radius r) (height infinity))))
; 1st Brillouin zone of a triangular lattice:
(define Gamma (vector3 0 0 0))
(define M (vector3 0 0.5 0))
(define K (vector3 (/ -3) (/ 3) 0))
(define Brill (list Gamma M K Gamma))
(set! k-points (interpolate k-interp Brill))
(set-param! resolution 32)
(set-param! num-bands 8)
(run-zeven)
Thanks,
Frederic.
--
Frederic Brossard
Cavendish Laboratory
J J Thomson Avenue
Cambridge CB3 0HE
UK
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