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ABSTRACT: We 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.
01/2011;
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ABSTRACT: We investigate optomechanical forces on a nearly lossless scatterer, such as
an atom pumped far off-resonance or amicromirror, inside an optical ring
cavity. Our model introduces two additional features to the cavity: an isolator
is used to prevent circulation and resonant enhancement of the pump laser field
and thus to avoid saturation of or damage to the scatterer, and an optical
amplifier is used to enhance the effective $Q$-factor of the counterpropagating
mode and thus to increase the velocity-dependent forces by amplifying the
back-scattered light. We calculate friction forces, momentum diffusion, and
steady-state temperatures to demonstrate the advantages of the proposed setup.
12/2010;
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ABSTRACT: The fields in multiple-pass interferometers, such as the Fabry-Pérot cavity, exhibit great sensitivity not only to the presence but also to the motion of any scattering object within the optical path. We consider the general case of an interferometer comprising an arbitrary configuration of generic beam splitters and calculate the velocity-dependent radiation field and the light force exerted on a moving scatterer. We find that a simple configuration, in which the scatterer interacts with an optical resonator from which it is spatially separated, can enhance the optomechanical friction by several orders of magnitude.
Physical Review Letters 07/2010; 105(1):013602. · 7.37 Impact Factor
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ABSTRACT: We present a theoretical analysis of a novel scheme for optical cooling of particles that does not in principle require a closed optical transition. A tightly confined laser beam interacting with a trapped particle experiences a phase shift, which upon reflection from a mirror or resonant microstructure produces a time-delayed optical potential for the particle. This leads to a nonconservative force and friction. A quantum model of the system is presented and analyzed in the semiclassical limit. Comment: 7 pages, 6 figures
11/2009;
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ABSTRACT: We present a generic transfer matrix approach for the description of the
interaction of atoms possessing multiple ground state and excited state
sublevels with light fields. This model allows us to treat multi-level atoms as
classical scatterers in light fields modified by, in principle, arbitrarily
complex optical components such as mirrors, resonators, dispersive or dichroic
elements, or filters. We verify our formalism for two prototypical sub-Doppler
cooling mechanisms and show that it agrees with the standard literature.
10/2009;
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ABSTRACT: Cooling forces result from the retarded dipole interaction between an
illuminated particle and its reflection. For a one-dimensional example, we find
cooling times of milliseconds and limiting temperatures in the millikelvin
range. The force, which may be considered the prototype for cavity-mediated
cooling, may be enhanced by plasmon and geometric resonances at the mirror.
04/2009;
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ABSTRACT: We present a one-dimensional scattering theory which enables us to describe a wealth of effects arising from the coupling of the motional degree of freedom of scatterers to the electromagnetic field. Multiple scattering to all orders is taken into account. The theory is applied to describe the scheme of a Fabry-Perot resonator with one of its mirrors moving. The friction force, as well as the diffusion, acting on the moving mirror is derived. In the limit of a small reflection coefficient, the same model provides for the description of the mechanical effect of light on an atom moving in front of a mirror.
Phys. Rev. A. 03/2009; 79(5).
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ABSTRACT: We present a mechanism for cooling atoms by a laser beam reflected from a single mirror. The cooling relies on the dipole force and thus in principle applies to arbitrary refractive particles including atoms, molecules, or dielectric spheres. Friction and equilibrium temperatures are derived by an analytic perturbative approach. Finally, semiclassical Monte-Carlo simulations are performed to validate the analytic results. Comment: 9 pages, 11 figures. [v2: As published]
03/2009;
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ABSTRACT: We propose a scheme for simultaneously trapping and detecting single atoms near the surface of a substrate using whispering gallery modes of a microdisk resonator. For efficient atom-mode coupling the atom should be placed within approximately 150 nm from the disk. We show that a combination of red and blue detuned modes can form an optical trap at such distances while the back-action of the atom on the field modes can simultaneously be used for atom detection. We investigate these trapping potentials including van-der-Waals and Casimir-Polder forces and discuss corresponding atom detection efficiencies, depending on a variety of system parameters. Finally, we analyze the feasibility of non-destructive detection. Comment: 13 pages, 16 figures
01/2006;
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ABSTRACT: We investigate the possibility of using dielectric microdisk resonators for the optical detection of single atoms trapped and cooled in magnetic microtraps near the surface of a substrate. The bound and evanescent fields of optical whispering gallery modes are calculated and the coupling to straight waveguides is investigated using finite-difference time domain solutions of Maxwell's equations. Results are compared with semi-analytical solutions based on coupled mode theory. We discuss atom detection efficiencies and the feasibility of non-destructive measurements in such a system depending on key parameters such as disk size, disk-waveguide coupling, and scattering losses. Comment: 10 pages, 10 fugures
07/2004;
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ABSTRACT: We investigate the optical detection of single atoms held in a microscopic atom trap close to a surface. Laser light is guided by optical fibers or optical microstructures via the atom to a photodetector. Our results suggest that with present-day technology microcavities can be built around the atom with sufficiently high finesse to permit unambiguous detection of a single atom in the trap with 10μs of integration. We compare resonant and nonresonant detection schemes and discuss the requirements for detecting an atom without causing it to undergo spontaneous emission.
Phys. Rev. A. 04/2003; 67(4).
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ABSTRACT: We investigate the optical detection of single atoms held in a microscopic atom trap close to a surface. Laser light is guided by optical fibers or optical micro-structures via the atom to a photo-detector. Our results suggest that with present-day technology, micro-cavities can be built around the atom with sufficiently high finesse to permit unambiguous detection of a single atom in the trap with 10 $\mu$s of integration. We compare resonant and non-resonant detection schemes and we discuss the requirements for detecting an atom without causing it to undergo spontaneous emission.
10/2002;
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ABSTRACT: We present a time dependent quantum calculation of the scattering of a few-photon pulse on a single atom. The photon wave packet is assumed to propagate in a transversely strongly confined geometry, which ensures strong atom-light coupling and allows a quasi 1D treatment. The amplitude and phase of the transmitted, reflected and transversely scattered part of the wave packet strongly depend on the pulse length (bandwidth) and energy. For a transverse mode size of the order of $\lambda^2$, we find nonlinear behavior for a few photons already, or even for a single photon. In a second step we study the collision of two such wave packets at the atomic site and find striking differences between Fock state and coherent state wave packets of the same photon number. Comment: to appear in Phys. Rev. A
02/2002;
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ABSTRACT: Atoms coupled to optical fields confined in one and two spatial dimensions in solid state microstructures can experience very large light shifts if the driving frequencies are close to a resonance of the microstructures and an atomic transition. Using the simple example of a quasi one-dimensional waveguide structure we can analytically calculate the atomic AC Stark shift and the modifications of the light field induced by the presence of the atom. A large enhancement of the effective interaction strength is found due to a non uniform mode density. Experimentally this should be visible by monitoring the scattered light field as well as by the modification of the atomic trajectories bouncing from the evanescent light. Comment: 4 pages, 4 figures
08/2001;
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ABSTRACT: We extend an earlier semiclassical model to describe the dissipative motion of N atoms coupled to M modes inside a coherently driven high-finesse cavity. The description includes momentum diffusion via spontaneous emission and cavity decay. Simple analytical formulas for the steady-state temperature and the cooling time for a single atom are derived and show surprisingly good agreement with direct stochastic simulations of the semiclassical equations for N atoms with properly scaled parameters. A thorough comparison with standard free-space Doppler cooling is performed and yields a lower temperature and a cooling time enhancement by a factor of M times the square of the ratio of the atom-field coupling constant to the cavity decay rate. Finally it is shown that laser cooling with negligible spontaneous emission should indeed be possible, especially for relatively light particles in a strongly coupled field configuration. Comment: 7 pages, 5 figures
03/2001;
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ABSTRACT: We present a systematic semiclassical model for the simulation of the dynamics of a single two-level atom strongly coupled to a driven high-finesse optical cavity. From the Fokker-Planck equation of the combined atom-field Wigner function we derive stochastic differential equations for the atomic motion and the cavity field. The corresponding noise sources exhibit strong correlations between the atomic momentum fluctuations and the noise in the phase quadrature of the cavity field. The model provides an effective tool to investigate localisation effects as well as cooling and trapping times. In addition, we can continuously study the transition from a few photon quantum field to the classical limit of a large coherent field amplitude. Comment: 10 pages, 8 figures
10/2000;
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ABSTRACT: We study the zero temperature dynamics of Bose-Einstein condensates in driven high-quality optical cavities in the limit of large atom-field detuning. We calculate the stationary ground state and the spectrum of coupled atom and field mode excitations for standing wave cavities as well as for travelling wave cavities. Finite cavity response times lead to damping or controlled amplification of these excitations. Analytic solutions in the Lamb-Dicke expansion are in good agreement with numerical results for the full problem and show that oscillation frequencies and the corresponding damping rates are qualitatively different for the two cases. Comment: 9 pages, 8 figures
02/2000;
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ABSTRACT: We study the mutual interaction of a Bose-Einstein condensed gas with a single mode of a high-finesse optical cavity. We show how the cavity transmission reflects condensate properties and calculate the self-consistent intra-cavity light field and condensate evolution. Solving the coupled condensate-cavity equations we find that while falling through the cavity, the condensate is adiabatically transfered into the ground state of the periodic optical potential. This allows time dependent non-destructive measurements on Bose-Einstein condensates with intriguing prospects for subsequent controlled manipulation. Comment: 5 pages, 5 figures; revised version: added references
06/1999;
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ABSTRACT: We investigate the creation of a relative phase between two Bose-Einstein condensates, initially in number states, by detection of atoms and show how the system approaches a coherent state. Two very distinct time scales are found: one for the creation of the interference is of the order of the detection time for a few single atoms and another, for the preparation of coherent states, of the order of the detection time for a significant fraction of the total number of atoms. Approximate analytic solutions are derived and compared with exact numerical results. Comment: 10 pages, 8 figures (postscript)
03/1999;
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ABSTRACT: We study the dynamic diffraction of atoms by a standing light wave in the limit where the recoil shift is much larger than the atomic linewidth. We demonstrate the appearance of a damped Pendellösung as well as anomalous transmission, which is equivalent to optical pumping into dark superpositions of the same internal atomic state with different external momenta. As an example, we discuss the case of metastable He coupled to the ground state via an anti-Stokes - Raman transition. We show that besides leading to a very narrow velocity selection for the deflected atoms, this effect could, in principle, be used to build a large-angle coherent beamsplitter and a large-area interferometer for metastable helium. We calculate the signal contrast and flux including initial velocity spread and decoherence through spontaneous emission for such an interferometer.
Quantum and Semiclassical Optics Journal of the European Optical Society Part B 12/1998; 8(3):583.
