Determination of optical losses in AlGaN-based UVC multimode waveguides using monolithic LEDs and detectors on a single chip

Abstract

We report on the investigation of optical losses in AlGaN-based multimode waveguides in the ultraviolet-C spectral range. The optical losses were measured using a monolithic photonic integrated circuit incorporating light-emitting diodes, detectors, and waveguides fabricated from a single AlGaN heterostructure. Total optical losses of 27 cm−1 (117 dB/cm) were determined for silicon doped Al0.76Ga0.24N waveguides. Using Monte Carlo ray-tracing simulations, we were able to distinguish the scattering losses of 6 cm−1 from absorption losses of 21 cm−1. It was shown that this measurement technique is only reliable for short waveguides from 400 to 1000 μm as longer structures lead to an underestimation of the optical losses.