Research On Laser Power Stabilization Technology For Atomic Interferometer Using Stimulated Raman Transitions

Atomic interferometer has broad application prospects in the field of precision measurement and basic physical theory verification,and has become a current international research hotspot.In this thesis,based on the demand of atomic interferometer for the stability of laser power,the research on laser power stabilization technology has been launched,and the laser power control system has been developed.The main work of the thesis is summarized as follows:1.The technical principle of laser power stabilization is analyzed,and the realization plan of the developed system is clarified.The influence of the power noise of the probe beam and Raman beam on the phase noise of atomic interferometer is theoretically analyzed,and the technical indicators of the developed system is determined.2.A laser power stabilization technology based on optical feedback of a high split ratio optical splitter is proposed.It is theoretically analyzed that in a typical externally modulated laser power stabilization device,the stability of the split ratio of the beam splitter will directly affect the result of laser power stabilization.For the compatibility of high split ratio and high stability in a power-stabilized system,we design and manufacture a high-split-ratio nonpolarized plate beam splitter,whose split ratio is insensitive to variations of laser power,polarization,and ambient temperature.Based on the optical feedback of the designed splitter,the laser power is closed-loop controlled by an acousto-optic modulator,and finally the power was stabilized at 537 m W.A 6-hour long-term test is performed,the relative stability of laser power in terms of root mean square and peak to peak is 2.72×10^-4 and 1.60×10^-3,respectively.3.A technique for stabilizing the carrier sideband ratio based on optical beating method is proposed.The optical beating signal is generated by inserting a reference beam between the carrier and the+1 sideband,and the high-sensitivity power detector is used to extract the microwave power corresponding to the beating signal to construct a feedback control system for stabilizing the power ratio between carrier and+1st sideband.The experimental results show that the control bandwidth of the system reaches 52 k Hz,and the interference experiment of the system is carried out in the temperature range of26℃to 58℃using a hot air gun,which proves the anti-interference ability of the system against temperature.The peak-to-peak relative stability for 150-minute is 5.67×10^-6,and the Allan deviation reaches a minimum of 2.19×10^-7 at an averaging time of 400 s,which is improved by more than four orders of magnitude compared with the open-loop regime.4.Combining laser power stabilization technology and carrier sideband ratio stabilization technology,a laser power control system is developed.The experiment results of 8 hours show that the peak-to-peak stability of the laser power reaches 2.4%,the root-mean-square stability is 0.5%.The control bandwidth of the Raman optical power ratio reaches 130 k Hz.Within 3.5 hours,the peak-to-peak stability of the power ratio reaches 1.7×10^-5,and the root mean square stability is 2.9×10^-6.After theoretical estimation,the gravity measurement sensitivity introduced by the laser power noise is reduced to 7.8μGal/shot,the measurement accuracy introduced by the power ratio between two Raman beams is reduced from 160μGal to 0.02μGal.