Advanced Bends and Micro Ring Resonators in Silicon Nitride Photonic Waveguides for C-Band

We present the design and experimental evaluation of low-loss advanced bends in silicon nitride (SiN) waveguides for the C-band. The advanced bends, with a radius of 25 μm, exhibit a bending loss of approximately 0.025 dB per 90°, comparable to the loss of a circular bend with a radius of 50 μm. Consequently, the 25 μm radius advanced bend is proposed for routing in SiN photonic integrated circuits to reduce the overall footprint. Furthermore, the use of these advanced bends in micro ring resonators results in quality factors of 5.8 × 10³ and 5.5 × 10⁴, with relatively large free spectral ranges and extinction ratios for radii of 15 μm and 25 μm, respectively.