Upgrading a Rb-85 Atom Interferometer



Elertas, Gedminas
(2021) Upgrading a Rb-85 Atom Interferometer. PhD thesis, University of Liverpool.

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Abstract

Atom interferometry is proving to be one of the most precise technique in gravimetry and gravity gradiometry, measurements of gravitational acceleration and gravitation gradient, respectively, in addition to magnetometry, inertial sensing and many other fields. The high precision of these instruments has attracted applications in fundamental physics research. The potential of employing this technique for the searches in dark-sector physics initiated the building of an atom interferometer at the University of Liverpool. The interferometer is in an atomic drop configuration. It employs ultra-cold Rb-85 as the atomic medium and a two-laser optical system. The atom source loads about a hundred million Rb-85 atoms and cools them down to 15 μK. The interferometric beams are generated with a high-frequency acoustic-optical modulator. The coherent control of atomic states was achieved via Raby oscillations, and atom interferometry has been demonstrated via Ramsey fringes with velocity-insensitive interferometric beams. This success provided an opportunity for building a new atom interferometer capable of velocity-sensitive measurements. The new interferometer will be able to operate in both atom launch and drop configurations and has the main vacuum chamber with 23 viewports, compared to 10 previously. This allowed for the incorporation of a low-velocity atom source. Two prototypes, 2D MOT and Axicon MOT, are being developed. A high power laser generating 8 W of 780 nm light via frequency doubling was built to increase the number of atoms. Such high powers necessitated a reconstruction of the optical control circuit, also allowing for atomic launch, improved state selection, and spurious light reduction. An effective vibration isolation system was constructed. Combining passive isolation and active cancellation technology in a working device was a significant step towards high sensitivity measurements. A new interferometry beam system was prospected, employing an injection-locked modulated laser diode. The prototype of such a system was built. The system proved to be capable of generating phase-locked light separated by 3 GHz. Later, due to concerns of stability and power limitations, a previous interferometry beam system was redesigned and improved instead. It employs additional tampered amplifiers to increase the power and a separate laser with an electro-optical modulator for the higher single-photon detuning, both required for velocity-sensitive measurements.

Item Type: Thesis (PhD)
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 09 Feb 2022 15:26
Last Modified: 11 Feb 2022 01:14
DOI: 10.17638/03143439
Supervisors:
  • Coleman, Jonathon
URI: https://livrepository.liverpool.ac.uk/id/eprint/3143439