Enhancing broadband second harmonic generation in a thin film lithium niobate racetrack resonator with tunable-coupling
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.
Keywords
Cite
@article{arxiv.2605.23439,
title = {Enhancing broadband second harmonic generation in a thin film lithium niobate racetrack resonator with tunable-coupling},
author = {Olivia Hefti and Jean-Etienne Tremblay and Andrea Volpini and Jannis Holzer and Alberto Della Torre and Homa Zarebidaki and Charles Caër and Hamed Sattari and Camille-Sophie Brès and Davide Grassani},
journal= {arXiv preprint arXiv:2605.23439},
year = {2026}
}
Comments
14 pages, 9 figures