FINITE-ELEMENT MAXWELLS EQUATIONS MODELING OF ETCHED AIR DIELECTRIC BRAGG MIRRORS

The importance of diffraction losses in etched air/GaAs Bragg mirrors in waveguides is theoretically evaluated. A complete three-dimensional resolution of the Maxwell equations by a finite element method is per formed, and shows the great importance of diffraction into the substra te. Two cases are distinguished: the weak guiding case. where the inde x contrast between waveguide and substrate is low (example: GaAs/AlAs) , and the strong guiding case where this contrast is high, thanks to t he use of lower refractive index substrates, such as oxidized AlAs. Th e latter solution is found to be very promising since the diffraction losses into the substrate are practically eliminated. (C) 1997 America n Institute of Physics.