Ultrastable lasers serve as the backbone for some of the most advanced scientific experiments today and enable the ability to perform atomic spectroscopy and laser interferometry at the highest levels of precision possible. With the recent and increasing interest in applying these systems outside of the laboratory, it remains an open question as to how to realize a laser source that can reach the extraordinary levels of narrow linewidth required and still remain sufficiently compact and portable for field use. Critical to the development of this ideal laser source is the necessity for the laser to be insensitive to both short- and long-term fluctuations in temperature, which ultimately broaden the laser linewidth and cause drift in the laser’s center frequency. We show here that the use of a large mode-volume optical resonator with 2 m of optical fiber, which acts to suppress the resonator’s fast thermal fluctuations, together with stimulated Brillouin scattering optical nonlinearity presents a powerful combination that enables lasing with an ultra-narrow linewidth of 20 Hz. To address the laser’s long-term temperature drift, we apply two orthogonal polarizations of the narrow Brillouin line as a metrological tool that precisely senses a minute change in the resonator’s temperature at the level of 85 nK. The precision afforded by this temperature measurement enables new possibilities for the stabilization of resonators against environmental perturbation.

中文翻译：

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纳米开尔文温度自参考的超窄线宽布里渊激光器

超稳定激光器是当今一些最先进的科学实验的基础，并具有以尽可能高的精度执行原子光谱和激光干涉测量的能力。随着近来对在实验室外应用这些系统的兴趣日益浓厚，如何实现能够达到所需的窄线宽的非凡水平并且仍然足够紧凑和便于现场使用的激光源仍然是一个悬而未决的问题。开发这种理想的激光源的关键是，激光器必须对温度的短期和长期波动不敏感，最终会加宽激光器的线宽并引起激光器中心频率的漂移。我们在这里表明，使用具有2 m光纤的大模量光学谐振器来抑制谐振器的快速热波动以及受激布里渊散射光学非线性的使用提供了一种强大的组合，可以实现超窄激光发射线宽为20 Hz。为了解决激光器的长期温度漂移问题，我们将窄的布里渊线的两个正交极化用作计量工具，可以精确地感测谐振器温度在85 nK时的微小变化。这种温度测量所提供的精度为稳定谐振器抵抗环境扰动提供了新的可能性。与受激布里渊散射一起，光学非线性提供了一种强大的组合，能够以20 Hz的超窄线宽发射激光。为了解决激光器的长期温度漂移问题，我们将窄的布里渊线的两个正交极化用作计量工具，可以精确地感测谐振器温度在85 nK时的微小变化。这种温度测量所提供的精度为稳定谐振器抵抗环境扰动提供了新的可能性。与受激布里渊散射一起，光学非线性提供了一种强大的组合，能够以20 Hz的超窄线宽发射激光。为了解决激光器的长期温度漂移问题，我们将窄的布里渊线的两个正交极化用作计量工具，可以精确地感测谐振器温度在85 nK时的微小变化。这种温度测量所提供的精度为稳定谐振器抵抗环境扰动提供了新的可能性。