A tunable frequency-offset-locked laser system for cooling neutral atomic gases
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Date
2025-04
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University of New Brunswick
Abstract
Ultra-stable lasers are essential for quantum technologies, requiring precise control and agile frequency tuning. This thesis develops a modular laser locking architecture based on offset frequency locking (OFL) for a quantum gravimeter utilizing cold 87Rb atoms. Two OFL systems stabilize 1560 nm Slave lasers, frequency-doubled to 780 nm, by locking them to an ultra-stable 780 nm Master laser. From the beat frequency, the system uses a broadband frequency divider, a linear frequency-to-voltage converter, and an analog PID controller to achieve a broad locking range. We achieve a frequency-locking stability with an Allan deviation that reaches 3.10 kHz at 200 s, and a frequency agility of 250 MHz/ms. We use this system to generate sub-Doppler-cooled samples of 87Rb atoms and perform high-sensitivity spectroscopy of the 5P3/2 hyperfine excited states. These spectra enabled us to perform an absolute optical frequency calibration of the OFL system.