Publication
Photonics in the ultraviolet provides an avenue for key advances in biosensing, pharmaceutical research, and environmental sensing. However, despite recent progress in photonic integration, a technological solution to fabricate photonic integrated circuits (PICs) operating in the UV-C wavelength range, namely, between 200 and 280 nm, remains elusive. Filling this gap will open opportunities for new applications, particularly in healthcare. A major challenge has been to identify materials with low optical absorption loss in this wavelength range that are at the same time compatible with waveguide design and large-scale fabrication. In this work, we unveil that thermal silicon oxide (TOX) on a silicon substrate is a potential candidate for integrated photonics in the UV-C, by removing the silicon substrate under selected regions to form single-side suspended ridge waveguides. We provide design guidelines for low-loss waveguide geometries, avoiding wrinkling due to residual intrinsic stress, and experimentally demonstrate waveguides that exhibit optical propagation losses below 3 and 4 dB/cm at a wavelength of 266 nm with claddings of air and water, respectively. This result paves the way for on-chip UV-C biological sensing and imaging.