Two-dimensional photonic crystals coupled to one-dimensional Bragg mirrors

Planar two-dimensional (2-D) photonic crystals can be combined with a one-dimensional (I-D) Bragg mirror to control the quality factor and out-of-plane coupling of optical modes. We have investigated the optical properties of such structures fabricated on silicon. The optical properties are probed by the room-temperature photoluminescence of Ge/Si self-assembled islands as an internal source. We show that the enhancement of the quality factor can be obtained by controlling the thickness of the silicon upper layer in which the 2-D photonic crystal is etched and the air filling factor of the photonic crystal. Quality factors of 2200 around 1100mn are obtained by this method for bulk photonic crystals with a square lattice pattern. The experimental results are supported by three-dimensional (3-D) finite-difference time-domain calculations of the investigated structures.