| The high-precision accelerometer is the core sensor of inertial navigation and play an important role in basic theoretical research,national major projects,and defense infrastructure construction.The precision acceleration measurement technology based on cold atom interference has developed rapidly and has shown a broad application prospect.This paper aims at the application of cold atom interference in inertial measurement,and combines the fast preparation of Bose-Einstein condensate with atomic interference to develop a cold-atom interferometry acceleration measurement system based on optical waveguides.A more detailed theoretical analysis and experimental research were conducted.The main innovative work of the thesis is summarized as follows:1.An optical waveguide-based acceleration measurement method is proposed.Based on the inertial measurement principle of the Bragg diffraction Mach-Zehnder cold atom interferometer,the vacuum,electronics,optics and other modules of the acceleration measurement system were optimally designed.The external cavity diode laser has been independently developed.The line width of the laser is better than 100kHz,and the output power is about 70 mW.The continuous non-mode-hopping range is greater than 20 GHz.After magneto-optical trap,polarization-gradient cooling,and evaporative cooling,a pure Bose-Einstein condensate with temperature of 50 nK is prepared,then the ultracold atom cloud is adiabatically loaded into the linear optical waveguide,and achieved the interferometric acceleration measurement by applying?2-?-?2 three pulses with the same axial of the waveguide.In the case of T?28?1ms,the highest acceleration sensitivity obtained by the system is?35?a?10-3m/s2.2.An 87Rb atom Raman sideband cooling method based on two-dimensional optical lattice is proposed.The working principle of Raman sideband cooling is studied,and a detailed experimental scheme based on the 87Rb Raman sideband cooling is designed.By Raman sidebands cooling in the two-dimensional optical lattice,the best temperature of the atom cloud is about 1.5?K,which is an order of magnitude lower than the temperature after the polarization gradient cooling.This cooling method reduces the temperature without changing the spatial density of the atom cloud,and can greatly increase the phase space density,which can be used to achieve all-optical BEC,or as a pre-cooling scheme for evaporative cooling to improve the cooling efficiency.3.A laser phase locking scheme based on digital phase frequency detector is proposed.A compact,low-noise digital optical phase-locked board is designed for phase locking between two external cavity diode lasers.Different from traditional optical phase-locked loops in frequency reduction through microwave beats,this design uses a frequency divider to downconvert the beat signal and design an ultra-low phase noise RF generator as a reference signal,avoiding the use of additional commercial microwave and RF generators.In the experimental process,the slave laser is locked on the master laser stably,the frequency difference is adjustable in the range of 1 GHz to12 GHz,the beat line width between the two lasers is better than 1 Hz.With the master laser frequency jump 1 GHz,the transition time of slave laser following is about 10 ms.4.A far-detuned optical lattice experiment scheme based on an external cavity diode laser is proposed.Aligning the lattice,tuning the lattice and pulsing the tapered amplifier are described in detail.Based on the magneto-optical trap and polarization gradient cooling,the effects of the parameters such as the intensity and detuning of the optical lattice on the loading are experiemently investigated,and the adiabatic loading and unloading of cold atoms in the optical lattice were realized.The lattice vibration frequency is measured by the intensity-modulation method.The experimental results show that,with the help of the lattice,the temperature of atom cloud reduced to 1/3compared with free space polarization gradient cooling.The experimental system has a simple structure.Only through an external cavity diode laser and a tapered amplifier,it can achieve flexible control of various parameters of the optical lattice,and has great guiding significance for the design of the optical lattice system.The involved system design and conclusions have reference value for the experimental design of other alkali metal atom optical lattices.5.An all-optical method for the preparation of Bose-Einstein condensation is proposed.As the quantum numbers F and mF are independent from the dipole potential,the optical trap can confine the atoms to any hyperfine or Zeeman states.All-optical BECs are capable of more extensive experimental investigations.At the same time,all-optical BEC can reduce the time of evaporative cooling process,shorten the BEC preparation cycle,which will better meet the measurement frequency requirements in the field of precision measurement.During the experiment,the process of quadrupole magnetic trap compression and RF evaporative cooling is omitted.After PGC,the cloud was directly loaded into the optical dipole trap to escape the evaporative cooling,and a pure BEC was finally prepared.The temperature of the atom cloud is around 50nK,and the atom number is around 1×105. |
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