Graphene-based Transparent Nano-heater for Thermally-tuning Silicon Nanophotonic Integrated Devices

For the traditional metal heaters used for SOI (silicon-on-insulator)-nanowire de- vices, a thick SiO2 upper-cladding layer is usually needed between the metal heater and the silicon core to isolate metal absorption, which makes the thermal tuning be with low response speed, low heating e-ciency, and low maximal temperature. In this paper, we propose and demonstrate a graphene-based transparent nano-heater for SOI nanowires. The present transparent graphene nano-heater is designed to contact directly with the silicon core of an SOI nanowire by utilizing the transparency of graphene. The lack of the thick SiO2 upper-cladding layer between the heater and the core region helps make fast thermally-tuning nanophotonic integrated devices. It is also beneflcial to improve the heating e-ciency because the heating volume is shrunk signiflcantly. The graphene nano-heater is designed optimally to avoid any signiflcant excess loss for the guided modes in the SOI nanowires. For example, the theoretical propagation losses of TE- and TM- polarization modes of a 600nm-wide SOI nanowire with a 100nm-wide graphene nano-heater are as low as » 0:005dB/"m and » 0:013dB/"m respectively. With this graphene-based trans- parent nano-heater, we present a thermally-tuning silicon Mach-Zehnder interferometer (MZI). The power consumption to have … phase-shift is » 5:2mW and » 5:7mW for TE- and TM- polarization modes, respectively. The theoretical response time is » 4:4"s, which is about twice faster than that for the case of using a traditional metal heater. In addition, the temperature of the silicon core is almost the same as that of graphene nano-heaters. In contrast, for the case of traditional metal heaters, the silicon core has much lower temperature than the metal heater while the metal heater has a limited maximal operation-temperature. This indicates that one can achieve higher achievable temperature for the silicon core with the present graphene nano- heater than the traditional metal heater. Graphene can also be used as a heat conductor (other than heater) by utilizing its high thermal conductivity of up to 5300W/mK. The excellent ther- mal properties of graphene make it very useful to enable e-cient thermally-tuning nanophotonic integrated devices including optical switches, optical fllters, etc..