Inverse-designed single-step-etched colorless 3 dB couplers based on RIE-lag-insensitive PhC-like subwavelength structures

摘要: Inverse-designed free-form nanophotonic structures have shown great potential in designing ultra-compact integrated photonic devices, but strict fabrication requirements may hinder further applications. We propose here a photonic-crystal-like (PhC-like) subwavelength structure, which is insensitive to the lag effect that most common error. A colorless 3 dB coupler employing such structure designed, fabricated, and characterized. With only one-step etching, coupling region of our final device occupies compact footprint 2.72×2.72 μm. The simulated insertion loss each output port about 3.2 over 100 nm bandwidth around 1550 nm, measured losses both ports are 3.35 dB, on average, observable 60 with near zero imbalance.