Mid-infrared photonic crystal cavities in silicon

We demonstrate the design, fabrication, and characterization of silicon photonic crystal cavities realized in a silicon on insulator (SOI) platform, operating at a wavelength of 4.4 μm with a quality factor of 13,600. Cavity modes are imaged using the technique of scanning resonant scattering microscopy. To the best of our knowledge, this is the first demonstration of photonic devices fabricated in SOI and operating in the 4-5 μm wavelength range.