Design of a stable optical system with an injection-locked laser to cool quantum gases to ultracold temperatures

Abstract

Strongly-correlated fermions are ubiquitous in nature, from the quark-gluon plasma of the early universe to neutron stars found in outer space, they lie at the heart of many modern materials such as high-temperature superconductors, massive magneto-resistance devices and graphene, and present some of the most challenging problems in contemporary physics. A thorough understanding of strongly correlated fermions will be able to address a wide range of questions from fundamental physics to technological applications. However, such an understanding is often hindered by the complexity of the host systems themselves. In addition, they are very difficult to treat theoretically, either analytically or numerically, due to the exponential increase in complexity even for a fairly small number of interacting particles. On the other hand, ultracold gas experiments have been successful in setting fermions in a well-characterized environment with a broad degree of control over inter-species interactions. In these systems, one can add a single ingredient at a time (spin mixture, interactions, lattice, etc.), allowing for an incremental complexity, which is analoguous to a quantum simulator for directly testing many-body theories. In many cases, the properties of such systems are universal and experimental results can be directly applied to explain the behaviour of natural materials.

In this dissertation, I discuss about my Masters project which is devoted to the design of a stable optical system with an injection-locked laser to cool Lithium gases to ultracold temperatures in order for the Lithium atoms to be manipulated as required for the scientific experiments. The purpose of a stable optical system design is to have a steady time-invariant frequency and intensity control of the laser setup. The laser setup will be then used to cool down Lithium atoms to temperatures on the order of 40 μK by laser cooling. Subsequently, these ultracold Lithium atoms will be manipulated in the compound setup, already developed in our laboratory, to study the behaviour of the Bose and Fermi gases in the unitarity regime between the BEC-BCS crossover. I will summarise the relevant theory required for the design of such a system, and also highlight the experimental work carried out to realize it. The report culminates with a discussion on further work to be done in the future, and its utilization in the global compound apparatus used in the laboratory to study ultracold Bose and Fermi gases.