Mid-Infrared Suspended Group IV Photonics

The mid-infrared (MIR) wavelength region contains unique absorption fingerprints of many molecules and substances. Therefore, the main application area in the MIR can be sensing. Si and Ge are transparent in this range (Si up to $8\ \mu\mathrm{m}$, and Ge up to $15\ \mu\mathrm{m}$) and due to their excellent electrical and optical properties and CMOS compatibility they can offer suitable platforms for the realisation of compact MIR sensors. However, claddings used for the telecom wavelength range are usually not suitable at longer wavelengths due to high absorption, so alternative solutions need to be investigated. In this paper we present our recent results on suspended Si and Ge devices (waveguides, couplers and detectors) that can exploit full transparency ranges of Si and Ge.