The Mechanical Faraday Effect – Can it Actually be Measured?
Our project proposal addresses fundamental topics in modern optical and atomic physics, such as symmetry breaking, structured light, and the interplay between optics and mechanics on the nano and quantum levels. Our research groups have diverse expertise in the study of light-matter interactions; in Glasgow we work on understanding the theoretical aspects of these interactions, whilst in Hannover we implement experiments in the laboratory. The combination of both approaches is ideal as the feedback between the two groups will lead to greater insight into physical phenomena and the generation of new research questions which we could not approach individually.
There has been a substantial increase in interest in opto-mechanical effects in the past decade. For example, mechanical cooling of macroscopic objects has been established, and optical tweezers have been used for nano-optical and nano-mechanical measurements. Together with quantum optics, such work has an important impact on basic research in microscopy, sensing, and the achievement of long-established goals in nanotechnology. Our project will investigate problems within this theme, in particular, tackling the central question of how and to what extent mechanical degrees of freedom, such as translation and rotation, can be transferred from a highly focused light beam onto atoms.
This transfer has been achieved both for macroscopic optical elements, such as wave plates, and ultra-cold ensembles of atoms in a condensate, but not for hot atoms in a vapour cell.
The underlying physical system for our research proposal will be a hot atomic vapour cell. These are glass or quartz cells which typically enclose a shielded compartment of alkali or other atoms. The research on hot vapour cells has been well- established for a century and represents a robust platform for quantum technologies. With a new set of tools which have been established in the past 20 years in quantum optics, atomic vapour cells have gained renewed attention in
A well-known effect in the study of optics is the Faraday effect. This is the measurable rotation of the plane of polarization of light as it passes through a medium whilst in the presence of a magnetic field. The conservation of momentum tells us that any change to the angular momentum of the light (as implied by the rotation) must be accompanied by a change to the angular momentum of the atoms, i.e. they should experience a torque. Our aim is therefore an in-depth theoretical and experimental analysis of the mechanical effects which a configuration of laser beams will induce when applied to the atoms in a vapour cell. The experimental means of observing these effects will be via a second ‘probe’ laser beam applied to the vapour.
“I am really excited to work on this project. Not only because it will allow me to conduct research I would otherwise not have been able to, but also because it will allow me to work closely with a great group of people in Hannover and experience a new city.”
“By supporting this project, the Tandem Fellowship ties together two groups that, on the one hand, focus on theoretical predictions and, on the other hand, on experimental realization.“
Benjamin Butler is a theoretical physicist currently studying for his PhD at the University of Glasgow. He is interested generally in theories of quantum light-matter interactions, quantum optics, and the regimes in which classical and quantum physics become blurred.Benjamin completed his undergraduate degree at the University of Leeds in 2019, with an MPhys project which investigated the role of electromagnetic potentials in quantum theory, from canonical quantisation techniques to the Aharonov-Bohm effect. His PhD is being completed in the Quantum Theory group at Glasgow under the supervision of Dr Jörg Götte and Dr Stephen Barnett. His research focuses on structured light, optical angular momentum, and the mechanical degrees of freedom of light.
Denis Uhland started his PhD in Physics at the University of British Columbia in Vancouver in 2018. He studied ultracold atomic ensembles and used Feshbach resonances to form atomic dimers. He was also involved in projects regarding the BEC-BCS crossover regime and cross-calibration of atomic pressure sensors. In 2022, he joined the light & matter group at the Leibniz University Hannover to continue and finish his PhD. He focuses on the fundamental quantum effects of hot atomic vapor cells and uses them for light filtration, quantum sensing, and magnetometers.