Dynamic regulating of lasing mode in a whispering-gallery microresonator by thermo-optic effect

Realizing dynamic regulation of specific optical components while being easy to integrate with photonic circuits will have a revolutionary impact on tunable laser sources, active filters, and all-optical switching/integration. Here, we demonstrate a temperature tunable Ga-doped ZnO microresonator with a conductivity of ∼1.75 S/cm controlled by the injection current and realize point-to-point heating. The shift in the resonant wavelength with a tuning range of 2 nm for TE66 mode is achieved by the effect of current-induced temperature rising on the refractive index of the microresonator crystal, namely, the thermo-optic effect. Meanwhile, the thermo-optic coefficient of 16.7 × 10−4/K around the bandgap energy of ZnO is also obtained. This operating mode of electronically controlled temperature establishes a solid foundation for the practicality and integration of tunable lasers.