Efficient 2 \(\times\) 2 multimode switch employing \({\hbox {Sb}}_{2}{\hbox {Se}}_{3}\) phase change material for enhanced mode division multiplexing systems

Mode division multiplexing (MDM) technology represents a significant advancement in high-capacity optical data transmission in photonics integrated circuits (PICs). Among the critical components in MDM architecture are multimode switches that enable signals to be routed simultaneously along different waveguides. In this study, we present a two-mode 2\(\times\)2 optical switch utilizing an asymmetric directional coupler with \({\hbox {Sb}}_{2}{\hbox {Se}}_{3}\) as the phase change material which is designed at an ultra-compact footprint of 53 \({\upmu }\)m \(\times\) 6 \({\upmu }\)m. This switch effectively routes the first two transverse magnetic modes simultaneously over a broad bandwidth within the third telecommunications window, specifically from 1535 to 1565 nm. Our 3D finite-difference time-domain simulation results indicate that the switch exhibits a low insertion loss of 0.78 dB and a crosstalk level of \(-\)7.98 dB in the “on” state across the specified bandwidth. Furthermore, in the “off” state, the switch maintains favorable performance characteristics, achieving insertion loss and crosstalk values of less than 0.41 dB and \(-\)15.69 dB throughout the operational bandwidth.