Influence of the external coherent radiation on rubidium atoms in a magneto-optical trap

Kregar, Gordana (2014) Influence of the external coherent radiation on rubidium atoms in a magneto-optical trap. Doctoral thesis, Faculty of Science > Department of Physics.

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Abstract

In this dissertation a cloud of cold rubidium atoms confined in a magnetooptical trap (MOT) has been realized. The laser cooling and trapping technique was implemented in the Laboratory for femtosecond frequency comb spectroscopy at Institute of Physics for the first time, so this work opens a new area of research. The cloud of cold atoms, containing ~ 10^9 87^Rb, F_g = 2, in volume ~ 3 mm3, density of ~ 1011 atom/cm3 in typical MOT operating conditions was obtained. Detailed characterization of the cloud has been done and the Doppler model for the real atomic system of rubidium 87 atoms was applied to describe the radiative force. The main focus of this work is investigation of the coherent continuous (cw) or pulsed (femtosecond) radiation effects on rubidium atoms in MOT. Atomic motion in the trap can be described with a damped harmonic oscillator model. A new technique for monitoring cold cloud center of mass oscillations induced by cw laser, tuned to rubidium resonant transition has been introduced. With this method the basic trap parameters, such are spring constant, damping coefficient and atom temperature are determined. For various trap working conditions an effective saturation intensity of 87^Rb D1 (F_g = 2 → F_e = 2) transition is, for the first time, determined through experimentally and theoretically investigated rubidium excited F_e = 2 state population depending on the probe beam intensity. Also, the radiative force of the probe D1 laser on cold cloud is measured and theoretically modelled. Interaction of cold rubidium cloud with femtosecond (fs) pulses has been studied in three different experimental configurations; interaction of cold atoms with single fs train of pulses, with two in-phase counterpropagating fs pulses and with two out-of-phase counterpropagating fs pulses. In all three described geometries the LIF signal and radiative force are experimentally determined and compared with theoretical model, based on optical Bloch equations (OBE) for two energy level atom.

Item Type: Thesis (Doctoral thesis)
Keywords: magneto-optical trap, laser cooling and trapping of atoms, radiative force, trap spring constant and damping coefficient, cold atoms dynamics, cold cloud centre of mass oscillations, effective saturation intensity, femtosecond frequency comb
Supervisor: Ban, Ticijana
Date: 29 October 2014
Number of Pages: 153
Subjects: NATURAL SCIENCES > Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 28 Nov 2014 12:14
Last Modified: 28 Nov 2014 12:14
URI: http://digre.pmf.unizg.hr/id/eprint/3400

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