Electrical Thermo-Optic Tuning of Whispering Gallery Mode Microtube Resonator

We demonstrate a very simple electrically assisted technique for broad-range tuning of whispering gallery modes in microtube resonator, which is fabricated by embedding a FeCrAl heating wire with small resistance into a tapered silica microtube. The huge Joule heat generated by the heating wire can be effectively and thermally conducted to the microtube and consequently changes the path of the optical whispering gallery modes due to the thermo-optic effect. Experimental results show that such a device has a tuning range of 0.57 nm with excellent stability under the applied current of 200 mA, fast response (<;100 ms), and low power consumption (~0.1 mW). This makes it to have potentials in tunable filters or fast optical switches.