置于超高真空环境且控温的超稳光学腔的腔线宽及零膨胀温度点测定

Measurement of the Cavity Linewidth and the Zero-expansion Temperature of a Temperature-stabilized Ultra-stable Optical Cavity Placed in Ultra-High Vacuum Chamber

高精细度超稳光学法布里-珀罗腔可以提供高精度的频率标准和频率分辨能力,在光学频率原子钟和量子精密测量等领域发挥重要作用,将其控温至零膨胀温度点可进一步有效提高超稳光学腔共振频率的稳定度。实验中构建了一套由超低膨胀系数的微晶玻璃材料制作的球型平凹F-P腔,镀有1560.5 nm和637.2 nm双波长高反多层介质膜,放置于可以精确控温的超高真空系统中。利用射频调制边带法测量得到超稳光学腔的自由光谱区为3.145 GHz,腔线宽~100 kHz,得到超稳光学腔在设定波长的精细度可高达30 000以上。在此基础上通过倍频波导器件将1560.5 nm激光倍频至780.25 nm,利用超稳光学腔共振频率和铷原子饱和吸收谱的对比,获得超稳光学腔在不同温度下共振频率的精确数值,根据相对腔长变化测量超稳光学腔系统的热膨胀特性,拟合得到零膨胀温度为(10.688±0.115)℃。高精细度光学腔提供了稳定的频率基准,同时可有效压窄激光线宽,抑制相位噪声,是产生优质光源的重要工具。我们已将其优异的短期频率稳定性和极低的频率噪声应用于通过高稳定度的637.2 nm红光腔增强倍频实现高稳定度的318.6 nm窄线宽紫外激光,进一步用于铯原子单步里德堡直接激发和里德堡缀饰基态铯原子系综方面的研究。

High finesse ultra-stable optical Fabry-Perot(F-P) cavity can provide high-precision frequency standard and fine frequency resolution,it plays an important role in optical frequency atomic clock and quantum precision measurement,and controlling its temperature to the zero-expansion temperature can effectively improve the frequency stability.In the experiment,a set of spherical flat concave F-P cavities made of glass ceramics with ultra-low expansion(ULE) coefficient is designed and prepared.It is plated with 1 560.5 nm and 637 nm antireflection film and placed in an ultra-high vacuum system with accurate temperature control.Using the modulated sideband method,the free spectral range of the ultra-stable optical cavity is 3.145 GHz and the cavity linewidth is ~100 kHz.The fineness of the ultra-stable optical cavity in the set wavelength laser can be more than 30 000.On this basis,the 1 560.5 nm laser is doubled to 780.25 nm by the frequency-doubling waveguide device.By comparing the resonant frequency of the ultra-stable optical cavity with the saturated absorption spectra of the rubidium atom,the accurate value of the resonant frequency of the ultra-stable optical cavity at different temperatures is obtained.According to the change of the relative cavity length,the thermal expansion characteristics of the ultra-stable optical cavity system are measured,and the zero expansion temperature is(10.688 ± 0.115)℃.The high finesse optical cavity provides a stable frequency reference,and can effectively narrow the laser linewidth and suppress phase noise.It is an important tool for generating high-quality laser sources.We have applied its excellent short-term frequency stability and extremely low-frequency noise to the 318.6 nm narrow linewidth ultraviolet laser with high stability through 637.2 nm laser cavity-enhanced frequency doubling,and further applied it to the study of cesium atom single-step Rydberg direct excitation and Rydberg dressed ground state cesium atom ensemble.