Master Thesis Defense: Alkiviadis Zoumis

Laser noise stabilization for low frequency quantum back action cancellation

Lasers with low classical noise are required to probe an atomic spin ensemble to investigate quantum features. Amplitude noise limits pondermotive squeezing observed in light, a measure of quantum correlations between light and matter. At few kHz frequencies, meeting this requirement is challenging with commercially available lasers. In our experiment, a Ti:Sa laser serves as a probe for the atomic system—a Cesium vapor cell—that exhibits more than 30 dB of amplitude noise above shot noise below 30 kHz, resulting in a reduction in observed ponderomotive squeezing. To mitigate this noise, a power stabilization scheme is essential. The scope of this thesis is the design and implementation of a control loop for the suppression of laser intensity noise. The intensity noise of the laser has been characterized in the frequency domain. An experimental power stabilization scheme has been developed using an acousto-optic modulator as an actuator. The intensity noise of the laser has been reduced by an average of 20 dB within a bandwidth of 100 kHz. Finally, the performance of the stabilization scheme has been evaluated with the atomic system, leading to the observation of 3.6 dB ponderomotive squeezing.