Low-power thermo-optic switch based on polymer waveguide integrated with graphene heater.

We present a low-power thermo-optic (TO) switch based on a polymer waveguide integrated with a graphene heater for low power-consumption and fast operation. The graphene layer buried inside the waveguide core does not introduce a significant loss to the transverse-magnetic polarized light, which can enhance the overlap integration factor of the optical field and thermal field and, therefore, effectively improve the heating efficiency. Moreover, thanks to the simple and flexible processing technology of the polymer waveguide platform, an integrated processing method was developed to bury the graphene electrode heater inside the waveguide core, which can reduce the damage to the graphene layer. The graphene electrodes heaters buried in the two Mach-Zehnder interferometer arms were patterned by using the inductively coupled plasma etching process to form the air trench structure, which can further reduce the power consumption of the device. Compared with the traditional polymer waveguide TO switch using metal electrode, the switching power of our fabricated switch is almost three times lower. The measured extinction ratio of the device is 25 dB with a switching power of 3.28 mW, and the switching rise time and fall time are 96 μs and 112 μs, respectively. The proposed device structure with the burying method for a graphene heater inside the polymer waveguide can find applications in large-scale photonic integrated circuits required for low power-consumption.