原子干涉转动测量中的激光频率控制研究
发布时间：2019-04-26 20:26
【摘要】：原子干涉仪作为高灵敏度的惯性传感器可以精确测量重力加速度、引力常数、转动角速度等重要物理量,在惯性导航、大地勘探、环境监察等方面有重要的应用。因此,研制原子干涉仪具有重要科学意义和实用价值。原子干涉陀螺仪是一种精确测量转速的仪器,因其具有潜在的高灵敏度而受到广泛关注。原子干涉陀螺仪利用一对相位相干的Raman光操控原子实现干涉,该过程要高精度控制激光频率和相位。原子干涉过程中Raman光相位噪声会直接进入到干涉仪相移中,从而影响转动测量的精度。在课题组前期工作的基础上,我们利用光学锁相环技术实现了四脉冲原子干涉陀螺仪所需要的Raman光,在原子干涉仪对Raman光相位噪声比较敏感的频段(1kHz~100kHz),Raman光相位噪声被压制到-95dBc/Hz,满足课题组目前原子干涉陀螺仪研制需求。制备高质量的冷原子源是原子干涉陀螺仪需要解决的关键问题之一,我们课题组利用偏振梯度冷却的方法获得超冷原子喷泉,在偏振梯度冷却过程中需要改变冷却光的频率,之前方案是利用AOM的一级衍射光作为冷却光,在偏振梯度冷却过程中通过改变AOM驱动频率实现冷却光频率的变化,该方法受到AOM移频量变化范围的限制,移频的最大变化量为60MHz,而且衍射光频率变化伴随着光强的变化,不利于独立地调节影响原子喷泉质量的参数。为克服AOM的缺点,我们利用FVC(Frequency Voltage Converter)作为鉴频器实现冷却光的稳频和大范围移频,冷却光频率短期稳定性在1MHz以内,满足原子冷却囚禁阶段对冷却光频率稳定度的要求。FVC输出与输入信号频率成正比的电压信号,该电压信号通过与参考电压比较得到鉴频误差信号,在偏振梯度冷却阶段,改变参考电压的大小,比较器输出的误差电压信号调节冷却光激光器的输出频率,实现激光频率快速变化。实验结果表明,冷却光频率在0.8ms内最大移频为120MHz,满足偏振梯度冷却对光失谐量的需求。
[Abstract]:As a highly sensitive inertial sensor, atomic interferometer can accurately measure gravity acceleration, gravity constant, rotation angular velocity and other important physical quantities. It has important applications in inertial navigation, geodetic exploration, environmental monitoring and so on. Therefore, the development of atomic interferometer has important scientific significance and practical value. Atomic interference gyroscope (ADG) is a kind of instrument for measuring rotational speed accurately, which has been paid more and more attention because of its potential high sensitivity. Atomic interferometry gyroscope uses a pair of phase coherent Raman light to control atom interference. The laser frequency and phase should be controlled with high precision in this process. In the atomic interference process, the phase noise of Raman light will enter into the phase shift of the interferometer directly, which will affect the precision of rotation measurement. On the basis of the previous work of our research group, we use optical phase-locked loop technology to realize the Raman light required by the four-pulse atomic interferometry gyroscope. In the frequency band (1kHz~100kHz) which is sensitive to the phase noise of the Raman light, the atomic interferometer is very sensitive to the phase noise of the Raman light. The Raman optical phase noise is suppressed to-95 dBC / Hz, which can meet the needs of the research and development of atomic interference gyroscope (AIFG). The preparation of high-quality cold atom source is one of the key problems to be solved by atomic interference gyroscope. Our research group uses polarization gradient cooling method to obtain ultra-cold atomic fountain, which needs to change the frequency of cooling light in the process of polarization gradient cooling. The first order diffracted light of AOM is used as cooling light. In the process of polarization gradient cooling, the change of cooling light frequency is realized by changing the driving frequency of AOM. This method is limited by the range of frequency shift of AOM. The maximum change of frequency shift is 60 MHz, and the variation of diffraction light frequency is accompanied by the change of light intensity, which is not conducive to the independent adjustment of the parameters affecting the quality of atomic fountains. In order to overcome the disadvantage of AOM, we use FVC (Frequency Voltage Converter) as frequency discriminator to realize the frequency stabilization and wide range frequency shift of cooling light, and the short-term stability of cooling light frequency is within 1MHz. The FVC outputs a voltage signal that is proportional to the frequency of the input signal, which is compared with the reference voltage to obtain a frequency discrimination error signal, which is in the polarization gradient cooling phase, and meets the requirements for the stability of the cooling light frequency in the atomic cooling captivity phase, and the FVC output voltage signal is proportional to the input signal frequency. When the reference voltage is changed, the output frequency of the cooling laser is adjusted by the error voltage signal of the comparator to realize the rapid change of the laser frequency. The experimental results show that the maximum frequency shift of cooling light in 0.8ms is 120MHz, which meets the requirement of polarization gradient cooling for optical detuning.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH744.3
[Abstract]:As a highly sensitive inertial sensor, atomic interferometer can accurately measure gravity acceleration, gravity constant, rotation angular velocity and other important physical quantities. It has important applications in inertial navigation, geodetic exploration, environmental monitoring and so on. Therefore, the development of atomic interferometer has important scientific significance and practical value. Atomic interference gyroscope (ADG) is a kind of instrument for measuring rotational speed accurately, which has been paid more and more attention because of its potential high sensitivity. Atomic interferometry gyroscope uses a pair of phase coherent Raman light to control atom interference. The laser frequency and phase should be controlled with high precision in this process. In the atomic interference process, the phase noise of Raman light will enter into the phase shift of the interferometer directly, which will affect the precision of rotation measurement. On the basis of the previous work of our research group, we use optical phase-locked loop technology to realize the Raman light required by the four-pulse atomic interferometry gyroscope. In the frequency band (1kHz~100kHz) which is sensitive to the phase noise of the Raman light, the atomic interferometer is very sensitive to the phase noise of the Raman light. The Raman optical phase noise is suppressed to-95 dBC / Hz, which can meet the needs of the research and development of atomic interference gyroscope (AIFG). The preparation of high-quality cold atom source is one of the key problems to be solved by atomic interference gyroscope. Our research group uses polarization gradient cooling method to obtain ultra-cold atomic fountain, which needs to change the frequency of cooling light in the process of polarization gradient cooling. The first order diffracted light of AOM is used as cooling light. In the process of polarization gradient cooling, the change of cooling light frequency is realized by changing the driving frequency of AOM. This method is limited by the range of frequency shift of AOM. The maximum change of frequency shift is 60 MHz, and the variation of diffraction light frequency is accompanied by the change of light intensity, which is not conducive to the independent adjustment of the parameters affecting the quality of atomic fountains. In order to overcome the disadvantage of AOM, we use FVC (Frequency Voltage Converter) as frequency discriminator to realize the frequency stabilization and wide range frequency shift of cooling light, and the short-term stability of cooling light frequency is within 1MHz. The FVC outputs a voltage signal that is proportional to the frequency of the input signal, which is compared with the reference voltage to obtain a frequency discrimination error signal, which is in the polarization gradient cooling phase, and meets the requirements for the stability of the cooling light frequency in the atomic cooling captivity phase, and the FVC output voltage signal is proportional to the input signal frequency. When the reference voltage is changed, the output frequency of the cooling laser is adjusted by the error voltage signal of the comparator to realize the rapid change of the laser frequency. The experimental results show that the maximum frequency shift of cooling light in 0.8ms is 120MHz, which meets the requirement of polarization gradient cooling for optical detuning.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH744.3
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