Compact SOI Dual-Mode (De)multiplexer Based on the Level Set Method

Mode (de)multiplexer is an essential device in integrated multimode photonic systems. Here, we present a dual-mode (de)multiplexer that separates two input modes, TE0 and TE1, into two output ports while converting TE1 to TE0 mode. Based on the adjoint and level set method, the device features a small footprint of 9.4 mu m x 2.9 mu m, and a minimum feature size over 200 nm is achieved, affirming stable and reliable fabrication. Through simulations, we observed insertion losses of less than 0.28 dB for TE0 mode and 0.35 dB for TE1 mode within the wavelength range of 1500-1600 nm, accompanied by crosstalk levels lower than -30 dB. In our experimental tests, we achieved insertion losses of less than 0.89 dB for TE0 mode and 0.44 dB for TE1 modes within the 1530 nm to 1570 nm range, with crosstalk maintained below -25 dB. Furthermore, we conducted an experimental verification of the differences between the standard device and the boundary dilation/erosion device, observing an insertion loss degradation by 0.61 dB within a deviation range of +/- 40 nm, which demonstrates the device's robustness to the fabrication. The proposed devices exhibit exceptional performance and feature a compact structure, thus holding significant potential for the development of future multimode integrated photonic circuits.