Regensburg 2025 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 46: Optical Properties
HL 46.5: Vortrag
Donnerstag, 20. März 2025, 10:45–11:00, H15
Determination of optical losses at 265 nm in multimode AlGaN waveguides — •Verena Montag1, Martin Guttmann2, Bruno Marx1, Tim Wernicke1, and Michael Kneissl1,2 — 1Technische Universität Berlin, Institute of Solid State Physics, Hardenbergstraße 36, 10623 Berlin, Germany — 2Ferdinand-Braun-Institut, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
Many applications for ultraviolet photonic integrated circuits (UV PICs) like, e.g., biochemical sensing, solar-blind communication, and UV Raman spectroscopy require materials with a large bandgap energy to enable low optical losses. Currently, no ideal material has been identified that enables low loss waveguides and simultaneously the implementation of active and passive components in the UV spectral range. AlGaN is a promising material which is already successfully employed for the fabrication of UV light emitting diodes (UV-LEDs) and UV lasers. However, the optical properties of AlGaN, especially the absorption losses in AlGaN waveguides have not yet been studied in detail in the UVC spectral range. In this work, 200 µm wide AlGaN waveguides, UV-LEDs, and detectors were monolithically fabricated on AlN/sapphire wafers and the waveguide losses are determined. We were able to measure photocurrents > 1 nA using an integrated AlGaN-based photodiode. Also, an exponential decrease of the photocurrent with increasing waveguide length could be observed. However, Monte Carlo ray tracing simulations show that apart from absorption losses in the AlGaN waveguides also scattering losses from surface roughness have to be considered in order to fully explain the results.
Keywords: photonic integrated circuit; ultraviolet spectral range; optical losses; AlGaN