Low-power integrated optical amplification through second-harmonic resonance.

Dean, Devin J; Park, Taewon; Stokowski, Hubert S; Qi, Luke; Robison, Sam; Hwang, Alexander Y; Herrmann, Jason F; Fejer, Martin M et al. · Nature · 2026

basic_science · Level V

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Abstract

Optical amplifiers are fundamental to modern photonics, enabling long-distance communications<sup>1</sup>, precision sensing<sup>2,3</sup> and quantum information processing<sup>4,5</sup>. Erbium-doped amplifiers dominate telecommunications but are restricted to specific wavelength bands<sup>1,6</sup>, whereas semiconductor amplifiers offer broader coverage but suffer from high noise and nonlinear distortions<sup>7</sup>. Optical parametric amplifiers (OPAs) promise broadband, quantum-limited amplification across arbitrary wavelengths<sup>8</sup>. However, their miniaturization and deployment have been hampered by watt-level power requirements. Here we demonstrate an integrated OPA on thin-film lithium niobate that achieves >17 dB gain with <200 mW input power-an order of magnitude improvement over previous demonstrations. Our second-harmonic-resonant design enhances both pump generation efficiency (95% conversion) and pump power utilization through recirculation, without sacrificing bandwidth. The resonant architecture increases the effective pump power by nearly an order of magnitude compared with conventional single-pass designs, while also multiplexing the signal and pump. We demonstrate flat near-quantum-limited noise performance over 110 nm. Our low-power architecture enables practical on-chip OPAs for next-generation quantum and classical photonics.