Suspended silicon waveguides for long-wave infrared wavelengths

In this Letter, we report suspended silicon waveguides operating at a wavelength of 7.67 mu m with a propagation loss of 3.1 +/- 0.3 dB/cm. To our knowledge, this is the first demonstration of low-loss silicon waveguides at such a long wavelength, with loss comparable to other platforms that use more exotic materials. The suspended Si waveguide core is supported by a sub-wavelength grating that provides lateral optical confinement while also allowing access to the buried oxide layer so that it can be wet etched using hydrofluoric acid. We also demonstrate low-loss waveguide bends and s-bends. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.