LAUSR

Mode converters play an essential role in mode-division multiplexing systems. A reflective mode converter (RMC), which is utilized to accomplish the mode conversion in the contra-propagation process, can fold the optical path and realize the mode exchange in an optical network. In this paper, we propose and experimentally demonstrate an RMC based on a silicon subwavelength structure. It can convert the input fundamental mode (${\text{TE}_0}$TE0) into the first-order mode (${\text{TE}_1}$TE1) in a ${2.0}\;\unicode{x00B5} \text{m} \times {2.0}\;\unicode{x00B5} \text{m}$2.0µm×2.0µm footprint. The simulated insertion loss and cross talk are lower than 0.6 dB and $ - {20.3}\;\text{dB}$-20.3dB in 1525-1565 nm. Experimental results verify the functionality of the device. The measured insertion loss and cross talk are lower than 2.2 dB and $ - {16.2}\;\text{dB}$-16.2dB. To further prove the generality of the methodology, we design another two RMCs realizing the mode conversion functions of ${\text{TE}_0}$TE0 to ${\text{TE}_2}$TE2 and ${\text{TE}_0}$TE0 to ${\text{TE}_3}$TE3 modes. The simulated insertion losses are lower than 1.1 dB and 1.8 dB.