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A. Lambrecht

Publications and source records attributed to A. Lambrecht.

50 records · Page 3Linked to original sources
arXiv2006

Development of a high sensitivity torsional balance for the study of the Casimir force in the 1-10 micrometer range

We discuss a proposal to measure the Casimir force in the parallel plate configuration in the $1-10μ$m range via a high-sensitivity torsional balance. This will allow to measure the thermal contribution to the Casimir force therefore discriminating between the various approaches discussed so far. The accurate control of the Casimir force in this range of distances is also required to improve the limits to the existence of non-Newtonian forces in the micrometer range predicted by unification models of fundamental interactions.

quant-ph↗
arXiv2006

The Casimir effect within scattering theory

We review the theory of the Casimir effect using scattering techniques. After years of theoretical efforts, this formalism is now largely mastered so that the accuracy of theory-experiment comparisons is determined by the level of precision and pertinence of the description of experimental conditions. Due to an imperfect knowledge of the optical properties of real mirrors used in the experiment, the effect of imperfect reflection remains a source of uncertainty in theory-experiment comparisons. For the same reason, the temperature dependence of the Casimir force between dissipative mirrors remains a matter of debate. We also emphasize that real mirrors do not obey exactly the assumption of specular reflection, which is used in nearly all calculations of material and temperature corrections. This difficulty may be solved by using a more general scattering formalism accounting for non-specular reflection with wavevectors and field polarizations mixed. This general formalism has already been fruitfully used for evaluating the effect of roughness on the Casimir force as well as the lateral Casimir force appearing between corrugated surfaces. The commonly used `proximity force approximation' turns out to lead to inaccuracies in the description of these two effects.

quant-ph↗
arXiv2006

Vacuum induced torque between corrugated metallic plates

We study the torque arising between two corrugated metallic plates due to the interaction with electromagnetic vacuum. This Casimir torque can be measured with torsion pendulum techniques for separation distances as large as 1$μ$m. It allows one to probe the nontrivial geometry dependence of the Casimir energy in a configuration which can be evaluated theoretically with accuracy. In the optimal experimental configuration, the commonly used proximity force approximation turns out to overestimate the torque by a factor 2 or larger.

quant-ph↗
arXiv2005

Surface plasmon modes and the Casimir energy

We show the influence of surface plasmons on the Casimir effect between two plane parallel metallic mirrors at arbitrary distances. Using the plasma model to describe the optical response of the metal, we express the Casimir energy as a sum of contributions associated with evanescent surface plasmon modes and propagative cavity modes. In contrast to naive expectations, the plasmonic modes contribution is essential at all distances in order to ensure the correct result for the Casimir energy. One of the two plasmonic modes gives rise to a repulsive contribution, balancing out the attractive contributions from propagating cavity modes, while both contributions taken separately are much larger than the actual value of the Casimir energy. This also suggests possibilities to tailor the sign of the Casimir force via surface plasmons.

quant-ph↗
arXiv1998

Frequency up-converted radiation from a cavity moving in vacuum

We calculate the photon emission of a high finesse cavity moving in vacuum. The cavity is treated as an open system. The field initially in the vacuum state accumulates a dephasing depending on the mirrors motion when bouncing back and forth inside the cavity. The dephasing is not linearized in our calculation, so that qualitatively new effects like pulse shaping in the time domain and frequency up-conversion in the spectrum are found. Furthermore we predict the existence of a threshold above which the system should show self-sustained oscillations.

quant-ph↗
arXiv1998

Generating photon pulses with an oscillating cavity

We study the generation of photon pulses from thermal field fluctuations through opto-mechanical coupling to a cavity with an oscillatory motion. Pulses are regularly spaced and become sharp for a high finesse cavity.

quant-ph↗
arXiv1998

Transverse effects on squeezing with atoms

We evaluate the squeezing of a probe beam with a transverse Gaussian profile interacting with an ensemble of two-level atoms in a cavity. We use the linear input-output formalism where the effect of atoms is described by susceptibility and noise functions. The transverse structure is accounted for by averaging atomic functions over the intensity profile. The results of the plane-wave and Gaussian-wave theories are compared. When large squeezing is predicted we find the prediction of the plane-wave model not to be reliable outside the Kerr domain. We give an estimate of the squeezing degradation due to the Gaussian transverse structure.

quant-ph↗
arXiv1998

Cold atoms: A new medium for quantum optics

Laser-cooled and trapped cesium atoms have been used as a nonlinear medium in a nearly resonant cavity. A study of the semiclassical dynamics of the system was performed, showing bistability and instabilities. In the quantum domain, squeezing in a probe beam having interacted with this system was demonstrated.

quant-ph↗
arXiv1998

Optical nonlinear dynamics with cold atoms in a cavity

This paper presents the nonlinear dynamics of laser cooled and trapped cesium atoms placed inside an optical cavity and interacting with a probe light beam slightly detuned from the 6S1/2(F=4) to 6P3/2(F=5) transition. The system exhibits very strong bistability and instabilities. The origin of the latter is found to be a competition between optical pumping and non-linearities due to saturation of the optical transition.

quant-ph↗
arXiv1998

The Casimir force for passive mirrors

We show that the Casimir force between mirrors with arbitrary frequency dependent reflectivities obeys bounds due to causality and passivity properties. The force is always smaller than the Casimir force between two perfectly reflecting mirrors. For narrow-band mirrors in particular, the force is found to decrease with the mirrors bandwidth.

quant-ph↗
arXiv1998

Atomic number fluctuations in a falling cold atom cloud

We evaluate the effective number of atoms in experiments where a probe laser beam with a Gaussian profile passes through an atomic medium consisting of a cold atom cloud released from a magneto-optical trap. Considering the case where the initial distribution is a Gaussian function of position and velocity, we give a quantitative description of the time variation of the effective atom number while the cloud is exploding and falling. We discuss the two cases where the effective number is defined from the linear and nonlinear phase shifts, respectively. We also evaluate the fluctuations of the effective atom number by calculating their correlation functions and the associated noise spectra. Finally we estimate the effect of these fluctuations on experiments where the probe beam passes through a cavity containing the atomic cloud.

quant-ph↗
arXiv1998

Transverse-mode coupling in a Kerr medium

We analyze nonlinear transverse mode coupling in a Kerr medium placed in an optical cavity and its influence on bistability and different kinds of quantum noise reduction. Even for an input beam that is perfectly matched to a cavity mode, the nonlinear coupling produces an excess noise in the fluctuations of the output beam. Intensity squeezing seems to be particularly robust with respect to mode coupling, while quadrature squeezing is more sensitive. However, it is possible to find a mode the quadrature squeezing of which is not affected by the coupling.

quant-ph↗
arXiv1998

Squeezing with cold atoms

Cold atoms from a magneto-optic trap have been used as a nonlinear medium in a nearly resonant cavity. Squeezing in a probe beam passing through the cavity was demonstrated. The measured noise reduction is 40% for free atoms and 20% for weakly trapped atoms.

quant-ph↗