1.2-µm-band ultrahigh-Q photonic crystal nanocavities and their potential for Raman silicon lasers.

Nanocavity devices based on silicon that can operate in the 1.2-µm band would be beneficial for several applications. We fabricate fifteen cavities with resonance wavelengths between 1.20 and 1.23 µm. Experimental quality (Q) factors larger than one million are obtained and the average Q values are lower for shorter wavelengths. Furthermore, we observe continuous-wave operation of a Raman silicon laser with an excitation wavelength of 1.20 µm and a Raman laser wavelength of 1.28 µm. The Q values of the nanocavity modes used to confine the excitation light and the Raman scattered light are about half of those for our Raman silicon laser operating in the 1.55-µm band. Nevertheless, this device exhibits an input-output characteristic with a clear laser threshold. Finally, we consider the effect of the higher scattering probability at shorter wavelengths on the Raman laser performance in the 1.2-µm band.