超稳激光系统中光学参考腔的热分析

发布时间：2019-04-28 18:17

【摘要】：基于光学参考腔的激光稳频技术广泛应用于各个领域,例如精密计量、高分辨率光谱学以及原子光钟等。目前采用PDH技术可以将激光的频率高精度地锁定在高稳定度的光学谐振腔的共振频率上。当鉴频信号的信噪比非常高时,激光频率的特性完全取决于光学参考腔的腔长稳定性。而外界的振动及温度的变化都会影响参考腔腔长的稳定性。目前主要通过对参考腔结构及支撑位置的设计来降低参考腔对外界振动的敏感度,并降低外界环境的振动,通常还将参考腔置于温控装置中。在采取了上述措施后,在大多数稳频激光系统中,激光频率在短时间内仍会出现一定的线性漂移,超过百秒时甚至会出现非线性的频率漂移。除了参考腔的老化引起频率漂移(10-17/s到10-16/s量级之间)外,最主要的原因是参考腔温度的微小抖动引起的腔长变化,从而使锁定在参考腔的激光发生频率改变。因此在对参考腔进行严格温控的同时,还需要降低参考腔的温度敏感度。本文致力于研究处于温控装置中的参考腔对外界温度变化的响应情况。首先推导出参考腔对外界温度变化响应的时间常数和温度敏感度的表达式,总结出影响参考腔温度敏感度的各个因素,提出有效降低温度敏感度的方法。结合ANSYS有限元分析,得出对于参考腔的热屏蔽层而言,其质量越大、比热容越高、热辐射率越小时,参考腔的时间常数越大、温度敏感度越低,另外通过增加屏蔽层的层数可大大降低参考腔的温度敏感度。结合以上结论提出了可根据实验的温控精度以及参考腔的热膨胀系数设计合理可行的屏蔽层结构。本文还讨论了热不均匀性引起的等效腔长变化量的大小,从而定量地分析了由于热不均匀性引起的频率不稳定度。另外通过有限元分析的方法设计出了零膨胀温度点在室温附近的复合材料的参考腔。
[Abstract]:Laser frequency stabilization technology based on optical reference cavity is widely used in many fields, such as precision measurement, high resolution spectroscopy and atomic optical clock. At present, the frequency of laser can be locked to the resonant frequency of optical resonator with high stability by using PDH technology. When the signal-to-noise ratio of the frequency discrimination signal is very high, the characteristics of the laser frequency depend entirely on the stability of the cavity length of the optical reference cavity. The external vibration and temperature change will affect the stability of the reference cavity length. At present, the design of reference cavity structure and support position is mainly used to reduce the sensitivity of reference cavity to external vibration and to reduce the vibration of external environment. Usually, the reference cavity is also placed in the temperature control device. After taking the above measures, in most frequency stabilized laser systems, the laser frequency will still appear a certain linear drift in a short period of time, and even nonlinear frequency drift will occur when the laser frequency exceeds 100 seconds. In addition to the frequency drift caused by the aging of the reference cavity, the main reason is the variation of the cavity length caused by the small jitter of the temperature of the reference cavity, which results in the frequency change of the laser locked in the reference cavity. Therefore, it is necessary to reduce the temperature sensitivity of the reference cavity while strictly controlling the temperature of the reference cavity. In this paper, the response of the reference cavity in the temperature control device to the change of the external temperature is studied. Firstly, the expressions of time constant and temperature sensitivity of the response of the reference cavity to the external temperature change are derived. The factors affecting the temperature sensitivity of the reference cavity are summarized, and a method to effectively reduce the temperature sensitivity is proposed. Combined with the finite element analysis of ANSYS, it is concluded that the larger the mass, the higher the specific heat capacity and the smaller the thermal emissivity, the larger the time constant and the lower the temperature sensitivity of the reference cavity for the thermal shielding layer of the reference cavity. In addition, the temperature sensitivity of the reference cavity can be greatly reduced by increasing the number of shielding layers. In combination with the above conclusions, a reasonable and feasible shield structure can be designed according to the experimental temperature control accuracy and the thermal expansion coefficient of the reference cavity. The variation of equivalent cavity length caused by thermal inhomogeneity is also discussed in this paper, and the frequency instability caused by thermal inhomogeneity is quantitatively analyzed. In addition, the reference cavity of composites with zero expansion temperature near room temperature was designed by finite element analysis.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O437;TN249

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