Development of ultra-stable cryogenic silicon optical resonators for laser frequency stabilization

开发用于激光频率稳定的超稳定低温硅光学谐振器

基本信息

批准号：
279028307
负责人：
Professor Stephan Schiller, Ph.D.
金额：
--
依托单位：
Institut für Experimentalphysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/279028307?language=en
关键词：
Development ultra stable cryogenic silicon

项目摘要

Optical resonators with low sensitivity to temperature and mechanical forces are of great importance for precision measurements in the optical and microwave frequency domains. In the optical domain, they serve to stabilize the frequencies of lasers for spectroscopic applications, notably for optical atomic clocks, and for probing fundamental physics concepts such as the properties of space-time. Also, by conversion of ultra-stable optical frequencies to the radio-frequency domain via an optical frequency comb, radio-frequency sources with ultralow phase noise can be realized, applicable to, e.g., radar measurements with improved sensitivity. The conventional approach for ultra-stable optical resonators is the use of ULE (ultra-low expansion glass) material, operated at temperatures near room temperature. This necessarily leads to a level of Brownian length fluctuations which imposes a fundamental limit to the achievable frequency stability. Cryogenic operation of a resonator provides one avenue towards reduction of these Brownian fluctuations. This offers the possibility of reduction of laser frequency instability more than one order of magnitude lower than with ULE resonators. Crystalline cryogenic optical resonators are furthermore characterized by the near-absence of length drift thanks to the near-perfect lattice structure. Silicon optical resonators have recently been studied in two configurations: first, at 124 K, a silicon resonator has been used to stabilize a laser frequency to the fractional instability level of 1E-16 on short time scales. Second, in our own work, detailed characterizations of a silicon resonator at cryogenic temperature (1.5 K) were performed, which confirmed the potential of eventually leading to 1E-17 frequency instability. Based on these important proof-of-principle studies, we propose here to perform further developments on cryogenic silicon resonators at 1.5 K, with the goal of the first 2 years being to reach a frequency instability on the level of < 5E-17 for medium-long integration times 1E2 s - 1E4 s (with drift removal). This is an intermediate goal towards eventually reaching the 1E-17 level on both short and medium-long timescales, 1 s - 1E4 s To demonstrate the performance aimed for in our 2-year goal, a second cryogenic resonator system needs to be developed, since no reference having 5E-17 instability is available. It will be operated in the same cryostat as the first, existing resonator, and will allow intercomparisons via beat frequency measurements. Moreover, several key issues, previously identified, will be taken care of by implementing suitable subsystems: reduction or residual laser amplitude modulation, installation of an active vibration isolation to reduce cryostat vibrations, implementation of optical breadboards inside the cryostat, prestabilization of the laser to a room-temperature ULE resonator in order to achieve Hz-level linewidth.

对于光学和微波频域中的精确测量，对温度和机械力敏感的光谐振器非常重要。在光学结构域中，它们有助于稳定光谱应用激光器的频率，特别是用于光原子时钟，以及探测基本物理概念（例如时空属性）。同样，通过将超稳定的光学频率转换为射频频率梳子，可以实现具有超值相噪声的射频频率，例如，适用于，例如，具有提高灵敏度的雷达测量值。超稳定光谐振器的常规方法是使用ULE（超低膨胀玻璃）材料，该材料在室温附近的温度下运行。这必然导致一定程度的布朗长度波动，这对可实现的频率稳定性施加了基本限制。谐振器的低温操作为减少这些棕色波动提供了一个途径。这提供了比用ULE谐振器低多个数量级的激光频率不稳定性的可能性。晶体低温光学谐振器的特征是，由于近乎完美的晶格结构，长度漂移的差异。硅光谐振器最近通过两种配置进行了研究：首先，在124 K时，硅谐振器已被用来将激光频率稳定在短时间尺度上的1E-16的分数不稳定性水平。其次，在我们自己的工作中，进行了在低温温度（1.5 K）处对硅谐振器的详细特征，这证实了最终导致1E-17频率不稳定性的潜力。基于这些重要的原理研究，我们在这里建议在1.5 K处对低温硅共振器进行进一步的发展，最初两年的目的是达到频率不稳定性，以<5E-17的水平<5E-17的水平，用于中长的整合时间1e2 s-1e4 s（带有漂移去除）。这是最终在短时间和中间时间标准（1 S-1E4 s）中达到1E-17水平的中间目标，以证明我们为期两年目标中的性能，需要开发第二个低温谐振器系统，因为没有5e-17不稳定性的参考。它将与第一个现有谐振器以相同的低温恒温器操作，并将通过BEAT频率测量允许对间群体进行操作。 Moreover, several key issues, previously identified, will be taken care of by implementing suitable subsystems: reduction or residual laser amplitude modulation, installation of an active vibration isolation to reduce cryostat vibrations, implementation of optical breadboards inside the cryostat, prestabilization of the laser to a room-temperature ULE resonator in order to achieve Hz-level linewidth.