Eliminating the phase shifts arising from additional sidebands in an atom gravimeter with a phase-modulated Raman laser.

Abstract

The additional sidebands (ASBs) in a Raman laser will have a significant effect on the performance of atom gravimeters (AGs) based on phase-modulated Raman lasers. We propose a method of modulating the sideband-to-carrier ratio in Raman lasers to determine the magic time intervals where the phase shift induced by the ASB effect is minimized, and this method is demonstrated by experiments. Among these magic time intervals, some noise-immunity points are predicted. Based on the prediction and the result of the ASB effect changing with the interval time T between adjacent Raman pulses, an optimal magic time interval is selected. Therefore, the uncertainty to the gravity measurement induced by the ASB effect when the AG works at the magic time interval is reduced to 0.5 μGal. Furthermore, the ASB effect and its zero-phase points in four-pulse atom interferometers are also discussed. This work provides a clear way to eliminate the phase shift induced by the ASB effect in high-precision AGs employing phase-modulated Raman lasers.