Quantum Optics and Ghost Imaging
Entanglement is the quintessential quantum phenomenon, associated with the non-classical correlations between separate quantum systems. It is viewed increasingly as a resource for quantum communications and the processing of quantum information. Entangled photons can be generated through a process known as parametric downconversion, where a single photon ultraviolet photon enters a nonlinear crystal and is converted into two infrared photons. We are using holographic techniques to investigate the degree of spatial entanglement and produce filtered ghost-images which reveal the quantum nature of the light source.
Angular momentum of light & optical vortices
As they travel through space, some light beams rotate. Such light beams have angular momentum. There are two particularly important ways in which a light beam can rotate: if every polarisation vector rotates the light has spin, if the phase structure rotates the light has orbital angular momentum (OAM). The latter was realised only relatively recently (in 1992), and has an optical vortex along its axis. Our group has pioneered a number of experiments exploring the nature of the angular momentum of light, from the angular Doppler effect to a measurement of the OAM of single photons.
Optical tweezers
Microscopic particles can be held and moved with laser beams called optical tweezers. This technology has recently undergone a revolution with the addition of spatial light modulators (SLMs) — computer-controlled holograms — to the beam path, turning optical tweezers into very versatile micro-manipulation tools. We are part of this revolution, extending the possibilities of 3D optical manipulation.
Optics for environmental gas monitoring
Throughout the world there is growing concern over mankind's impact on the environment. Everybody is familiar with greenhouse gases and global warming. Working mainly with industrial collaborators such as Siemens, Shell, and British Gas, our group's work has led to a number of commercial instruments for environmental and pollution monitoring. Field trials have taken us from the local sewage works and deserted forests in Northern England to Sweden, a Middle-Eastern desert, and up an active volcano in the Mediterranean.
Medical optics for diagnostics and treatment
Optical instruments have a key role to play in new services and treatments within a modern health service. As a result of an ageing population and increasing expectations medical instrumentation is set to be a growth area for
the foreseeable future. Working mainly with clinicians at Ninewells Hospital in Dundee, our group's work has
included the development of optical systems relying upon tissue fluorescence to identify early cancers. Most
recently, applying our knowledge of gas detection to the identification of disease from tell-tale gases in exhaled breath.
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METATOYs: metamaterials (arguably) for light rays
If metamaterials could be built at the scale of meters and if they could be made to work for all optical wavelengths, the visual possibilities should be spectacular.
Unfortunately, it will take a little while to get there.
Meanwhile, we are mimicking a few of the visual properties of metamaterials using arrays of miniaturized lenses and prisms, which have many similarities with metamaterials.
We call these metamaterials for light rays (METATOYs).
Atom optics
The behaviour of atoms can be controlled by light fields, and in turn atoms influence the propagation of light. We are interested in manipulating atoms with shaped light beams, e.g. light carrying orbital angular momentum, and to store optical quantum information in the atomic states and coherences.
We have recently trapped the first Rubidium atoms in a vapour cell. Cold atom gases are a perfect medium to study spectroscopy and non-linear atom optics at low intensities.
Laser modes: fractals and Bose-Einstein Condensates (BECs)
The way a laser beam is shaped is complex: at the speed of light it bounces backwards and forwards in the laser resonator, and every bounce alters it. This process still holds many surprises, like for example the discovery that mechanisms present in the resonator tend to shape the beam into a fractal (it then has geometrical properties similar to clouds, mountains, and certain vegetables). It also has interesting analogies in quite different systems.
Video
Download a video, made in 2004, about the group's activity (concentrating on Miles's work) in mp4 format (8 MB), mpg format (29.1 MB) or wmv format (10.8 MB).
Posters
Scattered across the walls of our department are posters illustrating the work of the different research groups. Here are the Optics group's posters.
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