Standing-wave Laser Field Research Articles

Two-photon optical Ramsey spectroscopy of freely falling atoms

Using a simple semiclassical model, we explore ultrahigh-resolution optical two-photon spectroscopy of cold neutral atoms falling freely in a fountain. Considering atoms that interact with the same standing-wave laser field twice on their parabolic trajectories, and averaging over a Maxwellian velocity distribution, we predict a nearly Lorentzian line shape with just the natural linewidth. First-order Doppler shifts cancel even if the counterpropagating beams are slightly misaligned, and sub-Hertz resolution appears feasible with a fountain of modest dimensions.

Saturated fluorescence in a standing-wave laser field

An atom in a near-resonant standing-wave laser field emits light spontaneously from its upper level which shows a dip at resonance. This calculation gives the intensity emitted as a function of laser tuning and of the saturation parameter. The case of oppositely directed waves of unequal amplitudes is also treated.

Resonance fluorescence of an atom in a standing-wave laser field

The authors calculate the fluorescent spectrum of an atom driven by a standing-wave laser field which is exactly resonant with the atomic transition when the atom is at rest. The motion of the atom causes Doppler shifts which destroy the exact resonance and produces a spectrum which can have peaks at omega k= omega L+k.V+kL.vn where omega L is the laser frequency, kL.v is the Doppler shift and n is any integer.

Forces on atoms in a standing-wave laser field

A previous calculation of forces on atoms in external (dc) fields and in homogeneous traveling-wave laser fields is modified for the case of a standing-wave laser field. The case of intense laser fields, where the Rabi frequency is much greater than the natural decay rate of the atom, is described. A general result for any Doppler shift of the laser frequency due to the atomic motion is obtained. It is specialized to the two cases in which this shift is either much smaller or larger than the natural decay rate. In the first case, we get the same result as that of a previous calculation. The second case has not been discussed previously.

Diffraction of an Atomic Beam by Standing-Wave Radiation

Preliminary experimental results are reported for the deflection of Na atoms in an atomic beam by a transverse standing-wave laser field whose frequency is tuned between the two ground-state hyperfine components of the ${D}_{2}$ line. In contrast to the two experiments done previously, a splitting of the beam into two symmetric peaks whose separation increases with the electric-field is seen here. In addition, the data show evidence for atomic diffraction: a tendency for scattered atoms to acquire momentum in multiples of $2\ensuremath{\hbar}k$.

Diffraction pattern of atoms in a resonant standing wave laser field

We illustrate the diffraction pattern of an atomic beam for a resonant standing wave laser field, and stress its dependence on the angle of incidence. A maximum spread of the atomic beam is found to occur for an incidence angle close to, but different from normal incidence.

Trapping and storage of atoms in a laser field

Analysis of the possibility of spatial trapping of cold atoms in a standing-wave laser field is presented. It is shown that cold atoms can be trapped for a long time in region ≈ λ in a nonresonant standing-wave field. In a resonant standing-wave field cold atoms can be stored for a long time in the region determined by the cross-section of the laser beam. Trapping and storage together with cooling of atoms that has been suggested earlier allow us in specific cases to increase the sensitivity and the resolution of spectroscopic studies.

Precision Infrared Stark Spectra ofN14H2D Using Lamb Dip

By Stark tuning the ${\mathrm{N}}^{14}$${\mathrm{H}}_{2}$D molecule into optical resonance with a standing-wave laser field, which is intense and monochromatic, it has been possible to obtain a unique vibration-rotation line assignment and its transition matrix element, and to probe ground- and excited-state Stark splittings with precision. Stark splittings as narrow as 1.5 MHz (within a Doppler width of 82 MHz) are observed for the first time in an optically excited state using the Lamb dip.