Broadly tunable THz radiation through nonlinear microresonator

The degenerate mode interaction can possess a clear avoided mode crossing to manipulate the cavity mode spectra by a mode-splitting process under a strong mode-coupling condition in high-Q microresonators. Here, the mode splitting strength can be changed by controlling the pump-resonance effective detuning in a dispersion-managed Si3N4 microresonator through a differential thermo-optic effect. The splitting mode can locally facilitate the frequency matching in normal dispersion microresonators so that the tunable parametric oscillation can be observed by tuning pump-resonance detuning. A broadly tunable THz wave radiation is generated after injecting the tunable parametric oscillation into a bias-free photomixer at room temperature.