Ultra-broadband, compact, and high-reflectivity circular Bragg grating mirror based on 220 nm silicon-on-insulator platform.

A compact (4.49 μm × 4.54 μm) and ultra-broadband circular Bragg grating mirror with relaxed fabrication requirements is proposed and demonstrated based on the 220 nm silicon-on-insulator (SOI) platform. Based on FDTD-simulations, the proposed grating mirror can achieve a reflectivity of >90% over a ultrabroad bandwidth of 500 nm (1263 - 1763 nm), and a high reflectivity of >95% over a broad bandwidth of 397 nm (1340 - 1737 nm), which covers the entire E- to U-bands. The circular grating is fabricated, and the experimental measurement results exhibit a high reflectivity of 93% - 98% within the measured band of 1530 to 1610 nm, which agrees well with simulations. Based on the proposed broadband and high-efficiency circular Bragg mirror, a compact notch filter with high rejection ratio (>10 dB) and low transmission loss (<0.5 dB) is also fabricated and presented, and the proposed filter could find various potential applications in optical communications and sensing applications. With its ultrabroad bandwidth, high reflectivity and compact size, the proposed circular Bragg mirror is expected to be a promising element for large-scale photonic integrated circuits and applications which require ultra-broadband and high-efficiency on-chip reflections.