Rapid adiabatic couplers with arbitrary split ratios for broadband DWDM interleaver application

We experimentally demonstrate compact and broadband rapid adiabatic couplers (RACs) with arbitrary power split ratios, achieved through the combination of translational offset and waveguide width control. Fabricated RACs of four different target split ratios show power splitting within ±3 % of the design target over a 160 nm wavelength range. Using these RACs, we implement an 8-channel dense wavelength division multiplexing (DWDM) interleaver exhibiting < −20 dB crosstalk for the center eight channels with flat-top passbands. Over a broader wavelength range, the design maintains crosstalk below −10 dB across more than 40 channels with 100 GHz spacing, demonstrating the broadband capability and scalability of RAC-based photonic integrated circuits.