Enhanced SPDC in periodically poled TFLN via pump-only resonance

We investigate enhanced spontaneous parametric down-conversion (SPDC) in periodically poled thin-film lithium niobate (TFLN) using a pump-only resonant scheme. Unlike doubly resonant approaches, this method simplifies design constraints while maintaining broadband signal and idler extraction. By engineering high-Q ring resonators at the pump wavelength and optimizing directional couplers for critical coupling, we achieve significant intra-cavity power enhancement. Combined with high-fidelity periodic poling exhibiting a near-ideal 50% duty cycle, this approach improves SPDC efficiency and source brightness. The presented platform offers a scalable and fabrication-tolerant route toward compact, low-power quantum photonic sources for integrated applications.