Designs of photonic crystal nanocavities for stimulated Raman scattering in diamond

Abstract

Diamond is a good candidate for producing Raman laser due to its high first-order Raman gain coefficient. Since its Raman shift (~1,332.5 cm−1) is large compared to other solid-state materials, it is possible to produce a Raman frequency converter using diamond crystals. Photonic crystals can be employed for confining photons within periodic structures, the scale of which is on the order of the incident wavelength, making it convenient for integrating all-optical circuits. Combining the merits of both diamond and photonic crystals, we present two designs of photonic crystal nanocavities (in hexagonal and square lattice structures) which can produce stimulated Raman lasing with low-threshold power. After optimizing the photonic bandgaps, triple resonant modes with high Q and small modal volume are realized in each design by tuning the radii of dot defects in the nanocavities. Numerical simulations show that for such designs, the threshold power for generating Raman lasers in the range of a few hundred nano-Watts can be achieved.