Ultrahigh-Q photonic crystal nanocavities in wide optical telecommunication bands

We have studied the feasibility of extending the operating wavelength range of high-Q silicon nanocavities above and below the 1.55 μm wavelength band, while maintaining Q factors of more than one million. We have succeeded in developing such nanocavities in the optical telecommunication bands from 1.27 μm to 1.50 μm. Very high Q values of more than two million were obtained even for the 1.30 μm band. The Q values increase proportionally to the resonant wavelength because the scattering loss decreases. We have also analyzed the influence of absorption due to surface water. We conclude that high-Q nanocavities are feasible for an even wider wavelength region including parts of the mid-infrared.