On-Chip Silicon Photonic Controllable 2 X 2 Four-Mode Waveguide Switch

Multimode optical switch is a key component of mode division multiplexing in modern high-speed optical signal processing. In this paper, we introduce for the first time a novel 2 x 2 multimode switch design and demonstrate in the proof-of-concept. The device composes of four Y-multijunctions and 2 x 2 multimode interference coupler using silicon-on-insulator material with four controllable phase shifters. The shifters operate using thermo-optic effects utilizing Ti heaters enabling simultaneous switching of the optical signal between the output ports on four quasi-transverse electric modes with the electric power consumption is in order of 22.5 mW and the switching time is 5.4 mu s. The multimode switch exhibits a low insertion loss and a low crosstalk below - 3 dB and - 19 dB, respectively, in 50 nm bandwidth in the third telecom window from 1525 to 1575 nm. With a compact footprint of 10 mu m x 960 mu m, this device exhibits a relatively large width tolerance of +/- 20 nm and a height tolerance of +/- 10 nm. Furthermore, the conceptual principle of the proposed multimode switch can be reconfigurable and scalable in multifunctional on-chip mode-division multiplexing optical interconnects.