Cross-correlation measurements for the analysis of noise sources in a resonant laser propagating into an atomic vapor

Atomic clocks can be considered as the cornerstone of the development of GNSS (Global Navigation Satellite System), aerospace and telecommunication technologies. Without highly precise timekeeping devices, services such as GPS, Galileo, and COMPASS would not function effectively. The most advanced version of this technology is the pulsed optical pumping (POP) clock, which has been developed in Italy by the National Institute of Metrological Research (INRIM) and engineered by Leonardo S.p.A. Compact atomic clocks based on vapor-cells rely on the measurement of the absorption of a laser resonant with the atomic vapor. Various factors influence the quality of the absorption signal and, consequently, the performance of the atomic clock. Among these, atomic motion, plays a crucial role in determining the stability limit and precision of the device. This thesis presents a method for characterizing the spectrum of the atomic noise using a differential cross-correlation approach testing a standard atomic-vapor cell. In particular an optical setup and custom signal processing blocks (based on the Python programming language) have been implemented to optimize the spectrum acquisition. Results, presented in this work, prove the effectiveness of the cross-correlation technique in distinguishing different noise contributions in absorption spectroscopy.