Determining optical path difference with a frequency-modulated continuous-wave method

Abstract

A technique for determining the optical path difference (OPD) between two Raman beams using a frequency-modulated continuous-wave method is investigated. This approach greatly facilitates the measurement and adjustment of the OPD when tuning the OPD is essential to minimize the effects of the diode laser's phase noise on Raman lasers. As a demonstration, the frequencies of the beat note with different OPDs are characterized and analyzed. When the measured beat frequency is 0.367 Hz, the OPD between Raman beams is zero. The phase noise of the Raman laser system after implementation of zeroing of the OPD is also measured.

A phase-locked laser system based on double direct modulation technique for atom interferometry

“…In addition, the phase noise of beat note would also be degenerated seriously by environmental perturbations: vibration of optical devices, air current and temperature variation etc. In our previous work [20], the difference between propagation distances have been removed by using a technique named Frequency Modulated Continual Wave (FMCW) [21], meaning that the frequency noise of the ECDL becomes negligible compared with the other phase noise sources.…”