Ultra-compact broadband silicon microring filters with large FSR based on width-tapered Bezier Bends

A silicon microring resonator based on width-tapered Bezier bends is proposed and experimentally demonstrated for broadband wavelength division multiplexing (WDM) filtering. The ring waveguide employs compact 180° Bezier bends optimized by particle swarm optimization, with a simulated loss of only 0.02 dB per bend at an effective radius of 1.3 μ m. A deterministic mapping between power coupling coefficients and coupler geometries is established to facilitate direct structural design of the filter. The fabricated 8-channel WDM filter on 220 nm silicon-on-insulator platform supports 16 uniformly spaced wavelength channels spanning the S, C, and L bands (1500–1610 nm). The device exhibits a free spectral range (FSR) of 51.2 nm, 3-dB bandwidths of 3.26–5.17 nm, insertion losses of 0.56–1.86 dB, and adjacent-channel crosstalk below -15 dB without thermal tuning. The proposed design provides an ultra-compact and broadband approach to silicon microring filters with a large FSR for high-capacity WDM systems.