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

V. Kowallik¹, M. Guttmann², B. Marx¹, T. Wernicke¹, and M. Kneissl^1,2

Published in:

Appl. Phys. Lett., vol. 129, no. 1, pp. 012105, doi:10.1063/5.0325379 (2026).

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 27cm⁻¹ (117dB/cm) were determined for silicon doped Al_0.76Ga_0.24N waveguides. Using Monte Carlo ray-tracing simulations, we were able to distinguish the scattering losses of 6cm⁻¹ from absorption losses of 21cm⁻¹. It was shown that this measurement technique is only reliable for short waveguides from 400 to 1000µm as longer structures lead to an underestimation of the optical losses.

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