Developing a novel, non-invasive detection technique in hot and cold atomic systems based on spin noise spectroscopy (SNS)

Abstract

In this thesis, we report for the first time, the measurement of intrinsic spin-coherences from an ensemble of a cold rubidium atoms using non-invasive Faraday rotation fluctuation measurements. We employ off-resonant Raman coupling between the Zeeman states of a ground hyperfine level of rubidium atoms in a magneto-optical trap (MOT) to enhance the spin-coherences, and thereby detect it non-destructively using a far offresonant probe laser field. We have developed a comprehensive theoretical model based on optical Bloch equations (OBE) to study the characteristics of the Raman driven spin-coherences, and find a way to measure the quantity - intrinsic spin-relaxation rate(0) of the system under investigation. First, we have implemented the Raman driven technique to characterize the measurement methods in thermal rubidium atoms. We have compared the extracted value of 0 using Raman driven technique, with a separate measurement done using intrinsic spin noise spectroscopy (SNS) [1–5] technique. We have demonstrated a good qualitative and quantitative agreement in measuring 0 between these two techniques in thermal rubidium atoms. After this characterization, we have moved to the cold atom measurements, and implemented this technique to extract the value of intrinsic spin-relaxation rate,