Preparation of spin squeezed atomic states by optical phase shift measurement

In this paper we present a state vector analysis of the generation of atomic spin squeezing by measurement of an optical phase shift. The frequency resolution is improved when a spin squeezed sample is used for spectroscopy in place of an uncorrelated sample. When light is transmitted through an atomic sample some photons will be scattered out of the incident beam, and this has a destructive effect on the squeezing. We present quantitative studies for three limiting cases: the case of a sample of atoms of size smaller than the optical wavelength, the case of a large dilute sample and the case of a large dense sample.Comment: 18 page

Long-lived non-thermal states realized by atom losses in one-dimensional quasi-condensates

We investigate the cooling produced by a loss process non selective in energy on a one-dimensional (1D) Bose gas with repulsive contact interactions in the quasi-condensate regime. By performing nonlinear classical field calculations for a homogeneous system, we show that the gas reaches a non-thermal state where different modes have acquired different temperatures. After losses have been turned off, this state is robust with respect to the nonlinear dynamics, described by the Gross-Pitaevskii equation. We argue that the integrability of the Gross-Pitaevskii equation is linked to the existence of such long-lived non-thermal states, and illustrate this by showing that such states are not supported within a non-integrable model of two coupled 1D gases of different masses. We go beyond a classical field analysis, taking into account the quantum noise introduced by the discreteness of losses, and show that the non-thermal state is still produced and its non-thermal character is even enhanced. Finally, we extend the discussion to gases trapped in a harmonic potential and present experimental observations of a long-lived non-thermal state within a trapped 1D quasi-condensate following an atom loss process

Nanoparticles in SiH4-Ar plasma: Modelling and comparison with experimental data

Experimental and theoretical investigations for growth of silicon nanoparticles (4 to 14 nm) in radio frequency discharge were carried out. Growth processes were performed with gas mixtures of SiH4 and Ar in a plasma chemical reactor at low pressure. A distinctive feature of presented kinetic model of generation and growth of nanoparticles (compared to our earlier model) is its ability to investigate small"critical" dimensions of clusters, determining the rate of particle production and taking into account the influence of SiH2 and Si2Hm dimer radicals. The experiments in the present study were extended to high pressure (≥20 Pa) and discharge power (≥40 W). Model calculations were compared to experimental measurements, investigating the dimension of silicon nanoparticles as a function of time, discharge power, gas mixture, total pressure, and gas flow

Optical bistability in a GaAs based polariton diode

We report on a new type of optical nonlinearity in a polariton p-i-n microcavity. Abrupt switching between the strong and weak coupling regime is induced by controlling the electric field within the cavity. As a consequence bistable cycles are observed for low optical powers (2-3 orders of magnitude less than for Kerr induced bistability). Signatures of switching fronts propagating through the whole 300 microns x 300 microns mesa surface are evidenced.Comment: 5 pages 3 figure

Realizing a stable magnetic double-well potential on an atom chip

We discuss design considerations and the realization of a magnetic double-well potential on an atom chip using current-carrying wires. Stability requirements for the trapping potential lead to a typical size of order microns for such a device. We also present experiments using the device to manipulate cold, trapped atoms

In situ infrared absorption spectroscopy of dusty plasmas

In situ, time-resolved Fourier transform infrared spectroscopy was used to study particulate formation in rf discharges in mixtures of silane, argon, and nitrogen. The spectra were taken at a maximum rate of 20 Hz. The discharge conditions were chosen such that previous calibrations of the time evolutions of particle size and density could be used. The measurements indicate that the onset of the solid-state vibrational absorptions of the SiH and SiH2 bands only takes place after the nucleation and coagulation phase have finished; it coincides with the previously predicted start of the deposition of amorphous hydrogenated silicon on the particles. The dissociation of the silane feed gas is found to be in the range of 30%, and its time development suggests that also the large-scale dissociation of silane only starts after the coagulation phase. This is in agreement with previously observed trends for the electron temperature. If silicon partilces are grown in the plasma, and the silane flow is stopped, the Si particles stay trapped in the glow. The infrared measurements, however, show that they almost completely oxidize: the SiH/SiH2 vibrations disappear and a strong SiO vibration appears. If nitrogen gas is allowed into the plasma, the SiO vibration is replaced by a SiN vibration. © 1996 American Vacuum Societ

Box traps on an atom chip for one-dimensional quantum gases

We present the implementation of tailored trapping potentials for ultracold gases on an atom chip. We realize highly elongated traps with box-like confinement along the long, axial direction combined with conventional harmonic confinement along the two radial directions. The design, fabrication and characterization of the atom chip and the box traps is described. We load ultracold ($\lesssim1 \mu$K) clouds of $^{87}$Rb in a box trap, and demonstrate Bose-gas focusing as a means to characterize these atomic clouds in arbitrarily shaped potentials. Our results show that box-like axial potentials on atom chips are very promising for studies of one-dimensional quantum gases.Comment: 9 pages 4 figure

Producing and Detecting Correlated atoms

We discuss experiments to produce and detect atom correlations in a degenerate or nearly degenerate gas of neutral atoms. First we treat the atomic analog of the celebrated Hanbury Brown Twiss experiment, in which atom correlations result simply from interference effects without any atom interactions.We have performed this experiment for both bosons and fermions. Next we show how atom interactions produce correlated atoms using the atomic analog of spontaneous four-wavemixing. Finally, we briefly mention experiments on a one dimensional gas on an atom chip in which correlation effects due to both interference and interactions have been observed.Comment: to appear in conference proceedings "Atomic Physics 20

Evanescent-wave trapping and evaporative cooling of an atomic gas near two-dimensionality

A dense gas of cesium atoms at the crossover to two-dimensionality is prepared in a highly anisotropic surface trap that is realized with two evanescent light waves. Temperatures as low as 100nK are reached with 20.000 atoms at a phase-space density close to 0.1. The lowest quantum state in the tightly confined direction is populated by more than 60%. The system offers intriguing prospects for future experiments on degenerate quantum gases in two dimensions

Mean field effects in a trapped classical gas

In this article, we investigate mean field effects for a bosonic gas harmonically trapped above the transition temperature in the collisionless regime. We point out that those effects can play also a role in low dimensional system. Our treatment relies on the Boltzmann equation with the inclusion of the mean field term. The equilibrium state is first discussed. The dispersion relation for collective oscillations (monopole, quadrupole, dipole modes) is then derived. In particular, our treatment gives the frequency of the monopole mode in an isotropic and harmonic trap in the presence of mean field in all dimensions.Comment: 4 pages, no figure submitted to Phys. Rev.