Erling Riis
FOSA, Professor of Laser Physics

Research

The main themes of Erling’s research to date have been high-resolution atomic spectroscopy and the development of the highly specialised laser sources required for these experiments. A particular area of research has been atom optics and the use of lasers in precision tests of fundamental physical principles. These are applications that have a fundamental aim, but rely heavily on the development of new and specialised techniques, not least frequency stabilised and tunable laser sources.

The current research activities span the whole spectrum of Photonics Group activities from laser development to quantum gasses. The work on laser sources has included the development of a single-frequency Ti:Sapphire laser, which is now commercially available, but most recently concentrated on novel semiconductor gain media. The VECSEL (Vertical External Cavity Surface Emitting Laser) combines the advantages of a quantum well engineered semiconductor gain medium with the superior spectral and spatial quality of a solid state laser.

There are two distinct strands to current work on ultracold atoms and both are taking place in collaboration with Dr Aidan Arnold. The work on Bose-Einstein condensation (BEC) of Rb atoms has as one of its ultimate aims to study interferometry with atoms – when they are cold enough, they behave like quantum mechanical waves. The use of an optical interferometer as a sensitive tool for measurements dates back to the experiments of Michelson and Morley over a century ago. With the subsequent invention of the laser – the coherent source of light – optical interferometry has been developed into a ubiquitous technology for precision measurements. Many of these measurements can be done much more accurately with atoms – the BEC is the atomic equivalent to the laser.

Separate from this we are investigating laser cooling of a ‘different’ atom, namely Ca. This atom has a number of challenges and opportunities. The first challenge is that the atom needs to be cooled with blue light rather than the IR light we are used to from Rb. The blue light is obtained from one of our own laser systems. An interesting opportunity is the prospect of laser cooling Ca all the way to BEC, a thing, that cannot be achieved with alkali metals.

A few million cold Ca atoms add colour to the laser cooling labs.

Highlights

Research fellowship sponsored by industrial collaborator (NKT Research, Denmark), 2002-2005

Programme committee member for EQEC 2003; Chair of local organising committee, International Conference on Laser Spectroscopy (ICOLS) 2005

invited speaker 1st ESA international workshop on Optical Clocks 2005