Optimization of GaN Bent Waveguides in the Visible Spectrum for Reduced Insertion Loss.

The development of GaN-based photonic integrated chips has attracted significant attention for visible light communication systems due to their direct bandgap and excellent optical properties across the visible spectrum. However, achieving compact and efficient light routing through bent waveguides remains challenging due to high insertion losses. This paper presents a comprehensive investigation of GaN bent waveguides optimization for visible light photonic integrated chips. Through systematic simulation analysis, we examined the effects of bending angle, process optimization approaches, and geometric parameters on insertion loss characteristics. The back-side thinning process demonstrates superior performance compared to front-side etching, reducing the insertion loss of 90° bends from 1.80 dB to 0.71 dB. Further optimization using silver reflection layers achieves an insertion loss of 0.57 dB. The optimized structure shows excellent performance in the blue-green spectral range (420-500 nm) with insertion losses below 0.9 dB, providing practical solutions for compact GaN photonic integrated chips in visible light communications.