Laser Stabilization for the GRAVITES Experiment

One major difficulty in modern physics is combining general relativity and quantum mechanics; limited progress in this area is partly due to severe lack of experimental data. The GRAVITES experiment involves using a single-photon source to send photons through a Mach-Zehnder interferometer whose arms are at different heights to observe a gravitationally induced phase shift between the two paths. In this work, we focused on implementing the pre-stabilization setup to ensure sufficient precision for the measurement. We achieved this by building, testing, and characterizing a servo board, assembling the vacuum and thermal isolation chamber, and completing the setup by locking the laser to the reference interferometer. The servo board is necessary to detect and correct fluctuations in the laser's frequency while the vacuum and isolation chamber attenuate the optical fiber noise. We measured the servo board's noise spectrum using a high-precision spectrum analyzer, which revealed a noise level of approximately 10-7 Vrms/√Hz at 100 mHz, below the anticipated shot noise level of our photodetector.