Inverse Designed Silicon Mode Converters Based on the Direct Binary Search Algorithm

To satisfy the demand for communication capacity, the Mode Division Multiplexing (MDM) technique has been proposed as an emerging and promising technique. Silicon-based MDM system has attracted more attention due to the high contrast refractive index between silicon and silica. We have proposed a mode converter, which is significant to the MDM system. The direct binary search (DBS) algorithm and 3D full-vectorial finite difference time domain (3D-FV-FDTD) have been used to optimize the proposed mode converter. We have also fabricated the proposed mode converter with a compact footprint of 4.1 × 1.7 µm ² . The measured insertion loss and crosstalk have been 0.43 dB and -15.97 dB at the working wavelength of 1550 nm, respectively. Meanwhile, the insertion loss and crosstalk of the fabricated mode converter have been lower than 2.27 dB and -13.28 dB with a broad bandwidth of 130 nm, respectively.