Intermediate-Range Casimir-Polder Interaction Probed by High-Order Slow Atom Diffraction.

At nanometer separation, the dominant interaction between an atom and a material surface is the fluctuation-induced Casimir-Polder potential. We demonstrate that slow atoms crossing a silicon nitride transmission nanograting are a remarkably sensitive probe for that potential. A 15% difference between nonretarded (van der Waals) and retarded Casimir-Polder potentials is discernible at distances smaller than 51 nm. We discuss the relative influence of various theoretical and experimental parameters on the potential in detail. Our work paves the way to high-precision measurement of the Casimir-Polder potential as a prerequisite for understanding fundamental physics and its relevance to applications in quantum-enhanced sensing.

Scattering of slow metastable argon atoms by dielectric nanospheres.

The elastic scattering at low energy of metastable argon atoms with internal angular momentum J = 0 and 2 by dielectric nanospheres is investigated. The differential cross sections are calculated for both isotropic and anisotropic interactions. A polarization effect is clearly evidenced. The possible use of a metastable atom beam as a probe of an ensemble of nanospheres deposited on a passive substrate is examined.

Negative-index media for matter-wave optics.

We consider the extension of optical metamaterials to matter waves and then the down scaling of metaoptics to nanometric wavelengths. We show that the generic property of pulsed comoving magnetic fields allows us to fashion the wave-number dependence of the atomic phase shift. It can be used to produce a transient negative group velocity of an atomic wave packet, which results into a negative refraction of the matter wave. Application to slow metastable argon atoms Ar(3P2) shows that the device is able to operate either as an efficient beam splitter or an atomic metalens.

Atom symmetry break and metastable level coupling in rare gas atom-surface van der Waals interaction.

van der Waals interactions between an atom and a planar surface exhibit a quadrupolar component in D(2)(z)-D(2)/3 (D, atomic dipole; z, normal to surface). This coupling is responsible for an atom symmetry break, mixing levels of the same parity such as metastable 3P0, 3P2 levels of rare gas atoms. The strongly exoenergic 3P0-3P2 transition in Ar and Kr is observed by a time-of-flight technique, using as a surface the edge of a copper slit. The results confirm the predicted strong peaking of the angular distribution of inelastically scattered atoms and give a good estimate of the transition probability.

Selective reflection spectroscopy of a resonant vapor at the interface with a metallic layer.

We discuss the properties of selective reflection spectroscopy at the interface between a resonant vapor and a complex dense medium, such as a metallic film layered on a dielectric substrate. We show that in the approximation of a low-density vapor, the signal mixes up the absorptive and dispersive components of the "effective resonant susceptibility" of the vapor, with the mixture amount governed by simple laws of linear optics. Preliminary experiments performed at the interface between Cs vapor (D2, 852-nm line) and a silver-coated glass window are reported, that show qualitatively the effect of the atom-surface van der Waals interaction.

Van der Waals-induced spectral distortions in selective-reflection spectroscopy of Cs vapor: the strong atom-surface interaction regime.

Frequency-modulated selective-reflection spectroscopy of the 6S-7P Cs resonance line yields Doppler-free anomalous line shapes that we demonstrate to be fully dominated by the long-range atom-surface interaction potential. The spatial inhomogeneous broadening of the observed line shapes, as well as its dependence on the pressure, the nature of the dielectric window, and the light incidence angle, is fully interpreted with a z(-3) van der Waals attraction model. These experiments clearly prove the feasibility of a spectral analysis of atom-surface interactions.

Ultraviolet continuous-wave phase conjugation at 285 nm.

Phase conjugation by degenerate four-wave mixing has been performed with a cw UV source on the Mg I resonance line at 285 nm ((1)S(0)-(1)P(1)(0)). Experimental observations and a comparison with a simple reflectivity model are presented.

Efficient phase conjugation of a cw low-power laser diode in a short Cs vapor cell at 852 nm.

Up to 50% cw phase-conjugate reflectivity has been obtained with a 30-mW diode laser at 0.85 microm by means of resonant degenerate four-wave mixing on an optically thick, 1-mm-long Cs vapor cell. Self-oscillation of a Fabry-Perot cavity containing this Cs cell is demonstrated.

Angular dependence of phase conjugation in SF(6).

Optical phase conjugation by degenerate four-wave mixing in SF(6) was studied with a cw CO(2) laser. The intensity and angular dependence of reflectivity were measured for the 10.6-microm P(18) line. The results verify the predictions of the inhomogeneously broadened resonant two-level gas model.

Polarization characteristics of phase-conjugate mirrors obtained by resonant degenerate four-wave mixing.

Polarization properties of phase-conjugate (PC) mirrors obtained by degenerate four-wave mixing in resonant gas media are experimentally analyzed on various neon transitions and theoretically interpreted. We show that, because of the Doppler broadening of the decay rate of the gratings, these properties are rather insensitive to the relaxation processes in the gas phase. We demonstrate simple ways of characterizing PC mirrors with either lambda/2 birefringence (for cross-polarized pumps) or J-dependent linear dichroism (for parallel-pump polarization).

Doppler-free two-photon heterodyne spectroscopy by single-beam frequency modulation.

A new spectroscopic method for monitoring Doppler-free two-photon absorption signals is analyzed. Its principle consists of high-frequency modulation of one of the incident beams and the detection of the modulation induced by two-photon absorption in the intensity of the counterpropagating beam. The predictable advantages of this method are pointed out by comparing it with other techniques.

High-sensitivity nonlinear spectroscopy using a frequency-offset pump.

We report the development of a simple method for eliminating coherent background noise and fluctuations from saturation-spectroscopy signals. With this technique, which we believe will also be effective in two-photon and other types of nonlinear spectroscopy, we have routinely observed background-free saturation signals in I2 at 514.5 nm with signal-to-noise ratios within an order of magnitude of the fundamental quantum limit.