近日，美国国家标准与技术研究院的Kartik Srinivasan&Xiyuan Lu及其研究团队取得一项新进展。经过不懈努力，他们推进面向覆盖绿光能隙相干应用的片上克尔光学参量振荡研究。相关研究成果已于2024年8月21日在国际知名学术期刊《光：科学与应用》上发表。

本文中，研究人员通过实验展示了如何利用克尔光参量振荡器（Kerr OPO）在氮化硅微环谐振腔中，在接近780纳米的泵浦波长下，稳健地实现整个绿色波段的光发射。该研究的微环谐振腔几何结构针对绿光能隙发射进行了优化；特别是，研究人员引入了一种基于部分微环下切的色散工程技术，它不仅扩展了波长覆盖范围，还证明了对谐振腔尺寸变化的稳健性。

正如色散模拟所预测的那样，仅使用四个器件，研究人员就生成了150多个均匀分布在绿光能隙的波长。此外，我们通过展示连续频率调谐（>50吉赫兹）和窄光学线宽（<1兆赫兹），证明了克尔光参量振荡器在相干应用中的实用性。这项研究工作是在将非线性纳米光子学及其优势引入可见光谱方面迈出的重要一步。

据悉，克尔微谐振腔中的光参量振荡（OPO）可以有效地将近红外激光转移到可见光谱。然而，迄今为止，色散大多将输出波长限制在大于560纳米，尚未证明可以稳定地获取整个绿光光谱。事实上，用传统激光增益产生532纳米至633纳米之间的波长，即通常所说的“绿光能隙”，尤其具有挑战性。因此，有必要扩展克尔光参量振荡器的波长范围，并开发可靠的器件设计。

附：英文原文

Title: Advancing on-chip Kerr optical parametric oscillation towards coherent applications covering the green gap

Author: Sun, Yi, Stone, Jordan, Lu, Xiyuan, Zhou, Feng, Song, Junyeob, Shi, Zhimin, Srinivasan, Kartik

Issue&Volume: 2024-08-21

Abstract: Optical parametric oscillation (OPO) in Kerr microresonators can efficiently transfer near-infrared laser light into the visible spectrum. To date, however, chromatic dispersion has mostly limited output wavelengths to >560nm, and robust access to the whole green light spectrum has not been demonstrated. In fact, wavelengths between 532nm and 633nm, commonly referred to as the “green gap”, are especially challenging to produce with conventional laser gain. Hence, there is motivation to extend the Kerr OPO wavelength range and develop reliable device designs. Here, we experimentally show how to robustly access the entire green gap with Kerr OPO in silicon nitride microrings pumped near 780nm. Our microring geometries are optimized for green-gap emission; in particular, we introduce a dispersion engineering technique, based on partially undercutting the microring, which not only expands wavelength access but also proves robust to variations in resonator dimensions. Using just four devices, we generate >150 wavelengths evenly distributed throughout the green gap, as predicted by our dispersion simulations. Moreover, we establish the usefulness of Kerr OPO to coherent applications by demonstrating continuous frequency tuning (>50GHz) and narrow optical linewidths (<1MHz). Our work represents an important step in the quest to bring nonlinear nanophotonics and its advantages to the visible spectrum.

DOI: 10.1038/s41377-024-01534-x

Source: https://www.nature.com/articles/s41377-024-01534-x