Laser stabilization sits at the heart of many precision scientific experiments and applications, including quantum information science, metrology, and atomic timekeeping. Many of these systems narrow the laser linewidth and stabilize the carrier by use of Pound–Drever–Hall (PDH) locking to a table-scale, ultrahigh quality factor (Q), vacuum spaced Fabry–Perot reference cavity. Integrating these cavities to bring characteristics of PDH stabilization to the chip scale is critical to reducing their size, cost, and weight, and enabling a wide range of portable and system-on-chip applications. We report a significant advance in integrated laser linewidth narrowing, stabilization, and noise reduction by use of a photonic integrated 4.0 m long coil resonator to stabilize a semiconductor laser. We achieve a 36 Hz {1/}\pi${1/}\pi$-integral linewidth, Allan deviation of {1.8} \times {{10}^{- 13}}${1.8} \times {{10}^{- 13}}$ at 10 ms measurement time, and a 2.3 kHz/s drift—to the best of our knowledge, the lowest integral linewidth and highest stability demonstrated for an integrated waveguide reference cavity. This performance represents over an order of magnitude improvement in integral linewidth and frequency noise over previous integrated waveguide PDH stabilized reference cavities and bulk-optic and integrated injection locked approaches, and over two orders of magnitude improvement in frequency and phase noise than integrated injection locked approaches. Two different wavelength coil designs are demonstrated, stabilizing lasers at 1550 nm and 1319 nm. The resonator is bus-coupled to a 4.0 m long coil, with a 49 MHz free spectral range, mode volume of {1.0} \times {{10}^{10}}\;\unicode{x00B5}{\rm m}^3${1.0} \times {{10}^{10}}\;\unicode{x00B5}{\rm m}^3$, and 142 million intrinsic {Q}${Q}$, fabricated in a CMOS compatible, ultralow loss silicon nitride waveguide platform. Our measurements and simulations show that the thermorefractive noise floor for this particular cavity is reached for frequencies down to 20 Hz in an ambient environment with simple passive vibration isolation and without vacuum or thermal isolation. The thermorefractive noise limited performance is estimated to yield an 8 Hz {1/}\pi${1/}\pi$-integral linewidth and Allan deviation of {5} \times {{10}^{- 14}}${5} \times {{10}^{- 14}}$ at 10 ms, opening a stability regime that heretofore has been available only in fundamentally non-integrated systems. These results demonstrate the potential to bring the characteristics of laboratory-scale stabilized lasers to the integrated, wafer-scale compatible chip scale, and are of interest for a number of applications in quantum technologies and atomic, molecular, and optical physics, and with further developments below 10 Hz linewidth, can be highly relevant to ultralow noise microwave generation.

中文翻译：

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基于光子集成 4.0 m 线圈谐振器的 36 Hz 积分线宽激光器

激光稳定是许多精密科学实验和应用的核心，包括量子信息科学、计量学和原子计时。其中许多系统通过使用 Pound-Drever-Hall (PDH) 锁定到桌面级、超高品质因数 (Q)、真空间隔的法布里-珀罗参考腔来缩小激光线宽并稳定载流子。集成这些腔体以将 PDH 稳定特性带入芯片规模对于减小其尺寸、成本和重量以及实现广泛的便携式和片上系统应用至关重要。我们报告了通过使用光子集成 4.0 m 长线圈谐振器来稳定半导体激光器，在集成激光器线宽窄化、稳定性和降噪方面取得了重大进展。我们实现了 36 Hz {1/}\pi${1/}\pi$-积分线宽，艾伦偏差{1.8} \times {{10}^{- 13}}${1.8} \times {{10}^{- 13}}$在 10 ms 测量时间和 2.3 kHz/s 漂移——据我们所知，最低积分线宽和最高稳定性演示用于集成波导参考腔。与以前的集成波导 PDH 稳定参考腔和体光学和集成注入锁定方法相比，此性能表示积分线宽和频率噪声提高了一个数量级以上，并且与集成注入锁定方法相比，频率和相位噪声提高了两个数量级以上. 演示了两种不同波长的线圈设计，将激光稳定在 1550 nm 和 1319 nm。谐振器总线耦合到一个 4.0 m 长的线圈，自由光谱范围为 49 MHz，模式体积为{1.0} \times {{10}^{10}}\;\unicode{x00B5}{\rm m}^3${1.0} \times {{10}^{10}}\;\unicode{x00B5}{\rm m}^3$和 1.42 亿本征{Q}${Q}$，在兼容 CMOS 的超低损耗氮化硅波导平台中制造。我们的测量和模拟表明，在具有简单被动振动隔离且没有真空或热隔离的环境环境中，频率低至 20 Hz 时，该特定腔的热折射本底噪声可达到。热折变噪声限制性能估计产生 8 Hz {1/}\pi -${1/}\pi$积分线宽和{5} \times {{10}^{- 14}}的艾​​伦偏差${5} \times {{10}^{- 14}}$在 10 毫秒时，打开了一个迄今为止仅在基本非集成系统中可用的稳定机制。这些结果证明了将实验室规模的稳定激光器的特性带入集成的、晶圆级兼容的芯片规模的潜力，并且对于量子技术和原子、分子和光学物理中的许多应用以及进一步低于 10 Hz 线宽的发展可能与超低噪声微波产生高度相关。