1,720,984 research outputs found
Efficient optomechanical cooling in one-dimensional interferometers
No full textWe present a scattering model which enables us to describe the mechanical force, including the velocity dependent component, exerted by light on polarizable massive objects in a general one-dimensional optical system. We show that the light field in an interferometer can be very sensitive to the velocity of a moving scatterer. We construct a new efficient cooling scheme, ‘external cavity cooling’, in which the scatterer, that can be an atom or a moving micromirror, is spatially separated from the cavity
Trapping of 85Rb atoms by optical pumping between metastable hyperfine states
No full textWe describe an atom trapping mechanism based upon differential optical pumping between metastable hyperfine states by partially displaced laser beams in the absence of a magnetic field. With realistic laser powers, trap spring constants should match or exceed those typical of magneto-optical traps, and highly flexible tailored trap shapes should be achievable. In a proof-of-principle experiment, we have combined a 1D implementation with magneto-optical trapping in the orthogonal directions, capturing ~104 85Rb atoms
Cavity cooling of atoms: within and without a cavity
Full text linkWe compare the efficiencies of two optical cooling schemes, where a single particle is either inside or outside an optical cavity, under experimentally-realisable conditions. We evaluate the cooling forces using the general solution of a transfer matrix method for a moving scatterer inside a general one-dimensional system composed of immobile optical elements. Assuming the same atomic saturation parameter, we find that the two cooling schemes provide cooling forces and equilibrium temperatures of comparable magnitude
Atom guiding along high order Laguerre-Gaussian light beams formed by spatial light modulation
Full text linkA spatial light modulator (SLM) has been used to create high quality Laguerre-Gaussian (LG) light beams, which have been used to study the guiding of cold rubidium atoms. The SLM allows real-time variation of the hollow guiding beam and permits direct comparison of the guided atom fluxes for different LG modes with minimal adjustment of the other optical components. It is demonstrated that, by increasing the azimuthal index l of the Laguerre-Gaussian beam, the radiation pressure pushing the trapped atoms may be reduced while maintaining the same guided flux. This is the first comparative study of hollow beam atom guiding, and further demonstrates the versatility of the SLM for studies in atom optics.</p
Cooling atoms particles and polarisable objects using dissipative dipole forces
No full textOptical cooling methods are generally applicable to a very restricted range of species. As a means of overcoming this problem, we explore the effect of the retarded interaction of any polarisable particle (an atom, a molecule or even a micromirror) with itself, similarly to cavity-mediated cooling. We use the transfermatrix method, extended to allow us to handle moving scatterers, to explore the most general configuration of a mobile particle interacting with any 1D combination of fixed optical elements. Remarkably, this model allows a solution in closed form for the force acting on the particle, without any a priori restriction on the nature of the particle
Mirror-mediated cooling: a paradigm for particle cooling via the retarded dipole force
No full textThe dipole force, which is generally conservative and thus unable to cool or heat a particle’s motion, acquires a dissipative nature when invested with some form of memory. We consider here the use of a single mirror, placed at a suitable distance from the particle, as the delay element or memory. This geometry, which may be considered as the prototype for cavity-mediated cooling, itself offers a realistic cooling mechanism, and for a one-dimensional example we find cooling times of milliseconds and limiting temperatures in the milllikelvin range. The cooling force is in principle applicable to atoms, molecules, particles and nanostructures, and can be enhanced through the use of optical resonances, perhaps plasmonic or geometric in origin, in the mirror, and by the inclusion of gain within the optical feedback path
Scattering theory of cooling in optomechanical systems
No full textWe present a one-dimensional scattering theory, arising from the optomechanical coupling of the motional degree of freedom of scatterers to the electromagnetic field. Multiple scattering to all orders is taken into account, and the result is a versatile model that can be used to describe a wealth of effects, including optical molasses and novel interactions between atoms and cavities that could potentially lead to optical cooling mechanisms applicable to a wide range of species
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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