Optical cooling of atoms and molecules using nanostructured surfaces

Freegarde, Tim and Horak, Peter (2008) Optical cooling of atoms and molecules using nanostructured surfaces. New Frontiers in Micro and Nano Photonics, Florence, Italy. 23 - 26 Apr 2008.

Record type: Conference or Workshop Item (Paper)

Abstract

The dipole force, which avoids the closed cycle of pumping and spontaneous emission that renders laser cooling unsuitable for molecules, is conservative: without dissipation, particles entering a trap retain the energy to escape. Fortunately, dissipation need not involve spontaneous emission if it instead results from the decoherence or decay of the optical trapping field that is coupled to the particle. To enhance the weak attraction of an atom to its reflection, cavity-mediated cooling recycles light through multiple reflections, amplifying the force and the retardation - a process related to the mechanical amplification in a near confocal cavity [5]. Resonant cavities and structures can increase the retardation, but not the intensity, even when the atoms or particles lie outside them - e.g. when the cavity is the narrow-band coating of a single mirror. Plasmon resonances of a structured metal can enhance both the delay and the optical intensity. Such processes, possible with arrays of micromirrors, resemble speckle field cooling [6], except that spontaneous emission is again replaced by decay of the optical field, and offer a new class of cooling mechanisms in which weak cooling is extended over a broad array, rather than concentrated at the centre of a single external cavity.

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