Simultaneous Type‐0 and Type‐I Optical Parametric Oscillation in Submicron Poled Thin‐Film Lithium Niobate

ABSTRACT We demonstrate dual optical parametric oscillations in a thin‐film lithium niobate microring resonator enabled by polarization‐insensitive submicron periodic poling. Under degenerate backward quasi‐phase matching, the counter‐propagating signal and idler wavevectors cancel, such that the phase‐matching condition is determined solely by the pump wavevector. As a result, a single submicron poling period simultaneously supports both Type‐0 (TM TM + TM) and Type‐I (TM TE + TE) parametric interactions in the same device. Temperature‐controlled resonance alignment further enables selective activation of either polarization channel. We observe optical parametric oscillation with thresholds of 290 μW for the Type‐0 process and 3 mW for the Type‐I process, both comparable to state‐of‐the‐art on‐chip OPO thresholds. These results establish submicron poled TFLN as a compact and reconfigurable platform for polarization‐diverse parametric light generation.