Abstract
The paper describes a Raman-laser system with high performance for an absolute gravimeter that was based on 87Rb atom interferometer. As our gravimeter is a part of the standard acceleration of gravity of China, the Raman lasers’ characteristics should be considered. This laser system includes two diode lasers. The master laser is frequency locked through the frequency-modulation (FM) spectroscopy technology. Its maximum frequency drift is better than 50 kHz in 11 h, which is measured by home-made optical frequency comb. The slave laser is phase locked to the master laser with a frequency difference of 6.8346 GHz while using an optical phase lock loop (OPLL). The phase noise is lower than −105 dBc/Hz at the Fourier frequency from 200 Hz to 42 kHz. It is limited by the measurement sensitivity of the signal source analyzer in low Fourier frequency. Furthermore, the power fluctuation of Raman lasers’ pulses is also suppressed by a fast power servo system. While using this servo system, Raman lasers’ pulses could be fast re-locked while its fast turning on again in the pulse sequence. The peak value fluctuation of the laser power pulses is decreased from 25% to 0.7%, which is improved over 35 times. This Raman-laser system can stably operate over 500 h, which is suited for long-term highly precise and accurate gravity measurements.
Highlights
As a novel inertial sensor, atom interferometry (AI) technique has developed into an ultra-precise measurement tool for fundamental constants [1,2,3,4] and rotations [5,6,7]
We present the Raman-laser system for an absolute gravimeter that is based on
The maximum frequency drifting of the beat note between two independent lasers is lower than 50 kHz during a period of 11 h measured by an optical frequency independent lasers is lower than 50 kHz during a period of 11 h measured by an optical frequency comb
Summary
As a novel inertial sensor, atom interferometry (AI) technique has developed into an ultra-precise measurement tool for fundamental constants [1,2,3,4] and rotations [5,6,7]. After the first demonstration of the pulsed atom gravimeter by Chu [8], it became a new method for the measurement of earth’s gravity field with high performance in both stability and accuracy [9,10,11,12,13]. In an AI gravimeter, a cold atom cloud realizes atom interference by interacting with a pair of Raman lasers to coherently split and later recombined while it is free falling down. It is directly impacted by the gravity measurement result by laser system’s characteristics, such as noise-level, stability, reliability, accuracy, and long-term continuous operation. We describe a Raman-laser system based on 87 Rb AI gravimeter and introduces its performance in phase noise, frequency and power stability, and long-term operation
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