Experimental Research On A Bragg Type Atom Interferometry Gravimeter

High-precision gravity measurements have significant application in geophysics research,gravity assisted navigation,fundamental physics research,etc.Due to the high precision of measuring the absolute value of the gravitational acceleration,cold atom interferometry gravimeter has received extensive attentions and rapid development in recent years.Increasing the phase shift caused by gravity is an important way to improve the performance of the atomic gravimeter.Atomic manipulation technology based on Bragg diffraction can increase the momentum difference of atomic wave packet in different interference paths,thus increases the scale factor and interference phase shift,which provides the possibility to further improve the resolution of atom interferometry gravimeter.The main task of my Ph.D.is to design and realize the atom interferometry gravimeter via Braggg diffraction based on the previous works in our group.The main contributions are as follows:(1)A set of high-power,low-phase-noise,frequency-doubling laser system from 1560 nm to 780 nm is designed and completed.The 780 nm light with a frequency doubling efficiency of 30%and a power up to 9 W is realized,which is used for the preparation of high-power Bragg and Raman light.(2)Atomic Bragg diffraction is realized,and the diffraction efficiency of n=4 order reaches 60%.The Bragg interferometry gravimeter based on Bragg diffraction is realized,which achieves a sensitivity of 4.5×10-8 g/Hz1/2(g = 9.8 m/s2)for gravity measurements,and the long-term resolution is 1.6 μGal(1μGal = 10-9g)with an integration time of 1000 s.A 3-day continuous gravity measurement was performed with a drift of less than 1 μGal.(3)We design and implement a momentum-resolved detection scheme based on Raman spectroscopy(RS)for the Bragg atom interferometer,which effectively solves the problem of overlapping atomic wave packets in final detection.With n=1 order and T =250 ms interferometer,it shows a sensitivity of 1.9×10-8 g/Hz1/2 for gravity measurements,reaching 7×10-10g at 1000 s.The sensitivity of our interferometer is nearly 3 times higher than the same type Bragg interferometer.(4)The magnetic field responses of Bragg type interferometer and Raman type interferometer are compared in the same device.It is verified that the Bragg interferometer is more insensitive to the magnetic field,which lays the foundation for further tests of the fundamental physical laws using Bragg interferometer.