Integrated high-quality factor silicon-on-sapphire ring resonators for the mid-infrared

We demonstrate high-quality (Q) factor grating-coupled ring resonators in a silicon-on-sapphire platform, operating at wavelengths between 4.3 and 4.6 mu m. Total Q-factors of 151 000 and intrinsic Q-factors of 278 000 are measured, representing the highest Q-factors measured at the mid-infrared in Si. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4791558]