Function-Versatile Thermo-Optic Switch Using Silicon Nitride Waveguide in Polymer

A function-versatile thermo-optic switch is proposed and experimentally demonstrated using silicon nitride waveguides embedded in polymer cladding. The device consists of a 1 x 2 input splitter, 2 single-mode waveguides for phase shifting, and a thermally controlled 2 x 2 output coupler to give another degree of freedom in achieving phase-matching conditions. Combining the high waveguide birefringence of the thin silicon nitride waveguide and the excellent thermo-optic property of the polymer material, this device can realize multiple functions by applying different micro-heater powers, i.e., polarization-independent path switching, beam splitting, and polarization beam splitting. For the polarization-independent path switching, the fabricated device has shown a crosstalk suppression better than 10 dB for the TE mode and over 20 dB for the TM mode in the wavelength range from 1500 nm to 1620 nm. For the polarization beam splitting function, the device can reach a polarization extinction ratio greater than 10 dB at selected bands. This simple yet scalable device may find applications in polarization-multiplexed optical communication technology and complex photonic computing networks.