Multi-Channel Parallel Silicon Mode-Order Converter for Multimode On-Chip Optical Switching

Various mode-order converters are implemented in optical mode multiplexing and mode switching systems. Typically, such devices can only accomplish one mode-order conversion function. In this paper, we propose a multi-channel parallel mode-order converter based on inverse-design optimization method. By using a QR-code-like silicon structure, it can realize the mode-order conversions of multiple mode channels simultaneously in a compact footprint. As a proof of concept, we design and demonstrate a dual-channel silicon mode-order converter, which converts TE0 mode to TE2 mode, and TE1 mode to TE3 mode. It has a footprint of 4 μm×3 μm. Simulation results show that the insertion losses for the two mode-order conversion process are 0.8-1.0 dB and 0.9-1.2 dB, and have good tolerance to temperature variations. The inter-mode cross-talk is lower than -19.9 dB and -17.4 dB. Experimental results show that its range of insertion losses for the two process fluctuate within 2.0-3.6 dB and 1.5-5.1 dB in the wavelength range of 1525-1565 nm. The inter-mode cross-talk is lower than -10.7 dB and -13.1 dB, respectively.