Tailoring of optical modes of semiconductor microcavities via metal and dielectric gratings.

We investigate optical mode tailoring in a semiconductor microcavity with a metal grating on top and a dielectric grating (DG) on the bottom. Strong coupling between microcavity and grating-diffraction modes is explained in the Fano-picture. The Fano resonance shows a weak dependence upon grating height and duty ratio, but is strong upon grating period. The microcavity transmission line shapes are "S" and anti "S"-type for the metal and DGs, respectively. Together with these two types of Fano resonances, the transmission spectra have been tailored into very sharp peaks with FWHM being up to 0.1 nm. We prove that this optical mode tailoring method is quite applicable for other waveguide-grating structures too.