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arXiv · 2605.23439

Enhancing broadband second harmonic generation in a thin film lithium niobate racetrack resonator with tunable-coupling

Olivia Hefti·Jean-Etienne Tremblay·Andrea Volpini·Jannis Holzer·Alberto Della Torre·Homa Zarebidaki·Charles Caër·Hamed Sattari·Camille-Sophie Brès·Davide Grassani
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Abstract

Second harmonic generation in thin film periodically poled lithium niobate (PPLN) is constrained by an efficiency-bandwidth trade-off and fabrication-sensitive scaling. We demonstrate a racetrack resonator incorporating a short PPLN section and a tunable Mach-Zehnder interferometer coupler that enables in situ control of the coupling condition, compensating fabrication tolerances and stabilizing operation near critical coupling. The telecom pump is resonantly enhanced, while the near-infrared second harmonic is generated in single pass, eliminating dual-resonance requirements. The device achieves a 35 times efficiency enhancement over a non-resonant structure while maintaining a 7 nm bandwidth. This architecture provides a robust platform for broadband integrated frequency doubling.

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Olivia Hefti, Jean-Etienne Tremblay, Andrea Volpini, Jannis Holzer, Alberto Della Torre, Homa Zarebidaki, Charles Caër, Hamed Sattari, Camille-Sophie Brès, Davide Grassani. 2026-05-22. Enhancing broadband second harmonic generation in a thin film lithium niobate racetrack resonator with tunable-coupling. https://arxiv.org/abs/2605.23439

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