Two-dimensional photonic crystals with germanium on insulator obtained by a condensation method

Germanium on insulator on silicon substrates can be obtained by the growth of a SiGe layer on silicon on insulator followed by a condensation at high temperature and a Ge epitaxial growth. We show that these substrates can be used for photonic devices. Two-dimensional photonic crystals with defect cavities have been fabricated. The emission at room temperature of condensed germanium can be spectrally controlled by varying the lattice parameter of the photonic crystals. Resonant emission is obtained between 1400 and 1700 nm when modifying the lattice periodicity between 400 and 480 nm for L3 cavities in a triangular lattice. Quality factors of 540 are obtained for the fundamental mode of the L3 cavity around 1600 nm. The experimental radiation pattern of the defect cavities is compared to the one calculated by a finite-difference time-domain method. A specificity of the germanium-on-insulator photonic crystals is that the optical sources are distributed within the whole material, by opposition to photonic crystals with a single quantum dot layer internal source.