C. I. Sukenik

Modulation-free laser frequency stabilization and detuning

We have developed a modulation-free technique for stabilizing a laser to a Doppler-free saturated absorption spectrometer without the need for phase sensitive detection. By using two acousto-optic modulators, we can lock, with variable offset, to atomic resonances. The new technique works equally well with both vapor and discharge reference cells. We demonstrate the technique using rubidium and metastable argon as references.

Coherent backscattering of light from ultracold and optically dense atomic ensembles

We review experimental and theoretical studies of coherent backscattering of near resonant radiation from an ultracold atomic gas in the weak localization regime. Recent accomplishments in high resolution spectroscopy of atomic ensembles based on the coherent backscattering process are discussed. We also propose several new experimental schemes for time-dependent spectroscopy as applied to multiple scattering in the regime of weak localization.

Hypersonic Wake Diagnostics Using Laser Induced Fluorescence Techniques

A review of recent research performed in iodine that involves a two photon absorption of light at 193 nm will be discussed, and it’s potential application to velocimetry measurements in a hypersonic flow field will be described. An alternative seed atom, krypton, will be presented as a good candidate for performing nonintrusive hypersonic flow diagnostics. Krypton has a metastable state with a lifetime of approximately 43 s which would prove useful for time of flight measurement (TOF) and a sensitivity to collisions that can be utilized for density measurements. Calculations using modest laser energies and experimental values show an efficiency of excited state production to be on the order of 10 −6 for a two photon absorption at 193 nm to the 6p[3/2]2 state.

Improved design of a frequency-shifted feedback diode laser for optical pumping at high magnetic field

Abstract We broaden the linewidth of an external cavity diode laser using frequency-shifted feedback from an intracavity acousto-optic modulator. The configuration employed allows for wider tunability than has been previously reported, allowing for easy tuning to the D1 or D2 line of 85Rb and 87Rb. We demonstrate the usefulness of the laser for optical pumping of Zeeman-split lines in the kilogauss regime.

Strong-field coherent backscattering of light in ultracold atomic 85Rb

We report experimental observations of polarization-dependent coherence loss occurring in strong-field multiple scattering of light in ultracold atomic 85Rb. A measure of coherence in multiple light scattering is the degree of contrast of the coherent backscattering enhancement from the vapour. For resonance saturation parameters up to 9, we see light-polarization-dependent modification of the backscattering enhancement, suggesting that inelastic atomic light scattering and dynamic atomic magnetization may play important roles in the multiple scattering process for 85Rb.

Alignment dynamics of slow light diffusion in ultracold atomic 85Rb

A combined experimental and theoretical investigation of time- and alignment-dependent propagation of light in an ultracold atomic gas of atomic {sup 85}Rb is reported. Coherences among the scattering amplitudes for light scattering off excited hyperfine levels produce strong variations of the light polarization in the vicinity of atomic resonance. Measurements are in excellent agreement with Monte Carlo simulations of the multiple scattering process.

A rf discharge cell for saturated absorption spectroscopy of metastable argon

We have produced a rf discharge in 40Ar and used saturated absorption spectroscopy to offset lock a Ti:Sapphire laser to the absorption peak of the 43P2→43D3 cooling transition at 811 nm. We describe the procedure for fabrication of the cell and production of the discharge.

Deflection of an atomic beam by the Casimir force

The force experienced by an atom inside a parallel‐plate waveguide is one of the basic phenomena of cavity QED. The full QED expression for this force is a complicated function, which depends upon the atomic oscillator strengths, the position of the atom, and the width of the cavity. For ground‐state atoms one can distinguish two simple limits. (i) When the gap is sufficiently small, the force takes on the form of a van der Waals interaction between the instantaneous electric dipole of the atom and its multiple images in the walls of the waveguide. (ii) In a large gap, when the atom is far from the walls, the van der Waals force is suppressed and the main force predicted by theory is due to the Casimir interaction of the atom with the cavity vacuum field. Whereas the van der Waals force between atoms and conductors has previously been studied experimentally, the Casimir force has not. Here we report the first observation of atom deflection by the Casimir force.

Measurements of population densities of metastable and resonant levels of argon using laser induced fluorescence

We present a new approach to measure population densities of Ar I metastable and resonant excited states in low temperature Ar plasmas at pressures higher than 1 Torr. This approach combines the time resolved laser induced fluorescence technique with the kinetic model of Ar. The kinetic model of Ar is based on calculating the population rates of metastable and resonant levels by including contributions from the processes that affect population densities of Ar I excited states. In particular, we included collisional quenching processes between atoms in the ground state and excited states, since we are investigating plasma at higher pressures. We also determined time resolved population densities of Ar I 2 p excited states by employing optical emission spectroscopy technique. Time resolved Ar I excited state populations are presented for the case of the post-discharge of the supersonic flowing microwave discharge at pressures of 1.7 and 2.3 Torr. The experimental set-up consists of a pulsed tunable dye lase...

Subsea LIDAR systems

Abstract: Oceanographic light detection and ranging (LIDAR) maps scattering layers, and relates their distributions to oceanographic processes. However, demonstrable links between this experimental technology and water column optical properties remain elusive. Theory shows the returned laser power (Pr) decays logarithmically as a function of depth-varying optical properties along the path of the beam. The decay slope is related to beam attenuation and diffuse attenuation coefficients, and the abundance of biogeochemical constituents, including phytoplankton. LIDAR quantification of phytoplankton distributions will improve predictions of ocean productivity, particularly in highly variable and rapidly changing polar environments. However, few observations exist to verify these relationships. Future ocean LIDAR development requires commercial systems capable of deployment in many environments to routinely profile the euphotic zone. Quantifying the distribution, abundance, and nature of scattering particles will improve estimates of ocean productivity, particle flux, and ocean biogeochemistry that are critical to understanding our changing ocean climate.