Dresden 2026 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 37: Nitrides II – Designed properties and LED

HL 37.3: Vortrag

Donnerstag, 12. März 2026, 10:00–10:15, POT/0006

Determination of optical losses in AlGaN-based multimode waveguides — •Verena Kowallik¹, Martin Guttmann², Leonardo Wildenburg¹, Tim Wernicke¹, and Michael Kneissl^{1, 2} — ¹Technische Universität Berlin, Institute for Physics & Astronomy, Berlin, Germany — ²Ferdinand-Braun-Institut (FBH), Berlin, Germany

Many applications for ultraviolet photonic integrated circuits (UV PICs), such as biochemical sensing, atomic clocks, and UV Raman spectroscopy, require materials with a large bandgap energy to facilitate low optical losses. One possible candidate are AlGaN alloys which are already successfully employed for the fabrication of UV light emitting diodes (UV-LEDs) and UV lasers. However, the optical properties of AlGaN materials, especially the absorption losses have not yet been studied in detail in the UVC spectral range. In this work, the absorption losses in 200   µm wide n-Al_0.76Ga_0.24N waveguides were investigated using monolithically integrated UV-LEDs emitting at 262 nm and detectors. By Monte Carlo ray-tracing simulations, we identified different contributions of the optical losses, namely, the propagation losses and scattering losses. Here, we implemented the waveguide surface roughness determined from atomic force microscopy images. Also, we investigated the portion of rays reaching the detector without beeing guided in the waveguide, e.g. scattered at the substrate’s backside or the AlN/sapphire interface.

Keywords: optical losses; photonic integrated circuit; PIC; ultraviolet