原子干涉轉(zhuǎn)動測量中的激光頻率控制研究
發(fā)布時間：2019-04-26 20:26
【摘要】：原子干涉儀作為高靈敏度的慣性傳感器可以精確測量重力加速度、引力常數(shù)、轉(zhuǎn)動角速度等重要物理量,在慣性導(dǎo)航、大地勘探、環(huán)境監(jiān)察等方面有重要的應(yīng)用。因此,研制原子干涉儀具有重要科學(xué)意義和實用價值。原子干涉陀螺儀是一種精確測量轉(zhuǎn)速的儀器,因其具有潛在的高靈敏度而受到廣泛關(guān)注。原子干涉陀螺儀利用一對相位相干的Raman光操控原子實現(xiàn)干涉,該過程要高精度控制激光頻率和相位。原子干涉過程中Raman光相位噪聲會直接進(jìn)入到干涉儀相移中,從而影響轉(zhuǎn)動測量的精度。在課題組前期工作的基礎(chǔ)上,我們利用光學(xué)鎖相環(huán)技術(shù)實現(xiàn)了四脈沖原子干涉陀螺儀所需要的Raman光,在原子干涉儀對Raman光相位噪聲比較敏感的頻段(1kHz~100kHz),Raman光相位噪聲被壓制到-95dBc/Hz,滿足課題組目前原子干涉陀螺儀研制需求。制備高質(zhì)量的冷原子源是原子干涉陀螺儀需要解決的關(guān)鍵問題之一,我們課題組利用偏振梯度冷卻的方法獲得超冷原子噴泉,在偏振梯度冷卻過程中需要改變冷卻光的頻率,之前方案是利用AOM的一級衍射光作為冷卻光,在偏振梯度冷卻過程中通過改變AOM驅(qū)動頻率實現(xiàn)冷卻光頻率的變化,該方法受到AOM移頻量變化范圍的限制,移頻的最大變化量為60MHz,而且衍射光頻率變化伴隨著光強(qiáng)的變化,不利于獨立地調(diào)節(jié)影響原子噴泉質(zhì)量的參數(shù)。為克服AOM的缺點,我們利用FVC(Frequency Voltage Converter)作為鑒頻器實現(xiàn)冷卻光的穩(wěn)頻和大范圍移頻,冷卻光頻率短期穩(wěn)定性在1MHz以內(nèi),滿足原子冷卻囚禁階段對冷卻光頻率穩(wěn)定度的要求。FVC輸出與輸入信號頻率成正比的電壓信號,該電壓信號通過與參考電壓比較得到鑒頻誤差信號,在偏振梯度冷卻階段,改變參考電壓的大小,比較器輸出的誤差電壓信號調(diào)節(jié)冷卻光激光器的輸出頻率,實現(xiàn)激光頻率快速變化。實驗結(jié)果表明,冷卻光頻率在0.8ms內(nèi)最大移頻為120MHz,滿足偏振梯度冷卻對光失諧量的需求。
[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.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：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.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TH744.3
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