The paper presents the results of the development of a laser-optical system for atomic interferometer based on rubidium atoms cooled to sub-Doppler temperatures. The laser-optical scheme was created to ensure the processes of cooling, pumping, and detecting atoms involved in interferometric measurements of free-fall acceleration. The system utilizes frequency doubled fiber lasers and broadband fiber electro-optical modulators. The choice of fiber lasers is driven by their high efficiency, narrow spectral line, low phase noise levels, as well as ease of operation and reliability. Laser frequency stabilization was carried out using modulation transfer spectroscopy and optical phase-locking methods. Experimental setups were described that allow the generation of multichromatic radiation and minimize spontaneous scattering by detuning from excited levels. It was noted that the design provides a full set of optical frequencies necessary for Raman spectroscopy. The amplitudes of frequency fluctuations of the cooling and pumping lasers were studied. It was shown that the implemented laser-optical system can ensure continuous operation of an atomic interferometer based on clouds of cold rubidium atoms, and an assessment of the fundamental sensitivity limit was conducted.
This thesis details the construction of a portable platform for cold atom experiments, as part of the European iSense project. This culminated in the demonstration of a working portable cold atom interferometer to the praise of the EC and reviewers during the final project meeting. Reductions in the size, weight and power consumption of all the crucial components for a cold atom system such as lasers, optics, magnetic field generation and electronics have been realised. These novel components have been integrated into a portable device that has been transported and operated by just two people. The completed device weighs 63 kg and uses 240 W power in a volume of just 61.1 litres. The system has generated a cloud of (6.7±0.7)x 10
6 rubidium-87 atoms at a temperature of 4.4 μK in 2 seconds using a mirror-MOT setup. The device has successfully performed atom interferometry in the form of a Ramsey interferometer both at the University of Birmingham, UK and also at an office in Brussels, BE after a journey of 570 km. A measurement of the hyperfine splitting of the ground state of rubidium-87 was performed and gives an uncertainty of
δω/
ω = 5.2 × 10
−7. The theoretical limit of the sensitivity to gravity of the iSense system is 3.9 μGal/√Hz.
Cold-matter-wave Sagnac interferometers possess many advantages over their thermal atomic beam counterparts when they are used as precise inertial sensors. We report a realization of a Sagnac-type interferometer with cold atoms. Cold rubidium atoms are prepared in a magneto-optical trap and are pushed by resonant laser pulse to form slow atomic beam. In the interference region, atomic wave packets are coherently manipulated using π/2−π−π/2 Raman pulse sequences. Interference fringes with maximum contrast of 37% are observed experimentally.