Dual-Mode 2 × 2 Thermo-Optic Switch Based on Polymer Waveguide Mach-Zehnder Interferometer

A dual-mode <inline-formula> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> thermo-optic switch based on Mach-Zehnder interferometer with symmetric directional couplers is proposed and experimentally demonstrated by utilizing polymer waveguides. The present switch consists of two <inline-formula> <tex-math notation="LaTeX">$2\times 2\,\,3$ </tex-math></inline-formula>-dB directional couplers, which are designed to be mode-insensitive by choosing the core separation and coupling length optimally. Meanwhile, a mode-insensitive phase shifter is employed to alter the phase of the two different modes simultaneously. With the switching power of ~9.0 mW, the measured extinction ratios for the E11 mode and E21 mode can reach to 17.5 dB and 16.4 dB, respectively, at 1550 nm, and the switching time is ~1.30 ms. The performance of the switch is also independent to the polarization state of light. Our proposed dual-mode switch with the advantages of low power-consumption can accommodate MDM system and would be applied in future large capacity communication systems.