Making the most of interference: the application of laser speckle and computer-generated holography to cold atoms

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• Graham Bruce (Strathclyde)
• Friday 19 May 2017, 12:00-13:00
• Physics East 217.

If you have a question about this talk, please contact Dr Giovanni Barontini.

In this talk, I will present our recent developments in two areas of optical science, and their application to cold atoms.

Speckle patterns result from the interference of multiple reflections in disordered media. This is regarded as a randomization process which destroys information contained within the initial beam and is deleterious to many optical systems. Indeed, many engineers study speckle to remove its effect. Intriguingly however, the processes that produce the speckle are entirely linear, and there is growing recognition that this complex pattern is rich in useful information on both the incident laser source and the environment, with startling potential uses. I will demonstrate our recent results, which show that speckle can be used as a sensitive probe of wavelength changes of the light, with a resolution below 1fm, and how this can be used to stabilize the wavelength of the source [1].

The development of new laser beam shaping methods is important in a variety of fields within optics, atomic physics and biophotonics. Spatial light modulators offer a highly versatile method of time-dependent beam shaping, based on imprinting a phase profile onto an incident laser beam that determines the intensity in the trapping plane laser field. The calculation of the required phase is a well-known inverse problem, which can be tackled with different approaches. Our method based on conjugate gradient minimisation [2] not only allows the calculation of smooth and accurate intensity profiles suitable for trapping cold atoms, but can also be used to generate multi-wavelength traps [3] and for simultaneous control over both the intensity and the phase of the light [4].

References:

[1] N K Metzger, et al., “Harnessing speckle for a sub-femtometre resolved broadband wavemeter and laser stabilization” Nat. Commun. (in press)

[2] T Harte, et al., “Conjugate gradient minimisation approach to generating holographic traps for ultracold atoms” Opt. Express 22, 26548 (2014)

[3] D Bowman, et al., “Multi-wavelength holography with a single spatial light modulator for ultracold atom experiments” Opt. Express 23, 8365 (2015)

[4] D Bowman, et al., “High-fidelity phase and amplitude control of phase-only computer generated holograms using conjugate gradient minimisation” Opt. Express 25, 11692 (2017)

This talk is part of the Cold atoms series.

This talk is included in these lists:

• Cold atoms
• Physics East 217

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