S. R. Hartmann

Photon echo relaxation in LaF3:Pr3+

Abstract We have observed deeply modulated photon echoes from Pr 3+ ions in LaF 3 reflecting nuclear hyperfine interactions in both the ground 3 H 4 and excited 3 P 0 states. We infer splittings of 0.75 MHz for the 3 P 0 state. Inhomogeneous broadening of the terminal levels is found to lead to echo modulation damping. A surprising concentration dependence of the photon echo relaxation rate is observed as well as a dramatically long-lived (3 min) stimulated photon echo.

Optical second-harmonic generation in atomic thallium vapor

Abstract We observe coherent optical second-harmonic generation in atomic thallium vapor when the fundamental is tuned to half the resonance frequency of the following transitions: 6 2 P 1 2 − 7 2 P 3 2 and 6 2 P 1 2 − 8 2 P 3 2 in the presence of a static magnetic field; and 6 2 P 1 2 − 7 2 P 1 2 , 6 2 P 1 2 − 8 2 P 1 2 in the absence of any external field .

Stimulated photon echo study of Na(32S12)-CO velocity-changing collisions

Abstract Using the recently developed single-state stimulated photon echo technique, we have studied the velocity changes experienced by ground-state Na atoms in collisions with carbon monoxide molecules. We find that the ground-state Na atoms have a total cross section of ≈420 A 2 for velocity-changing collisions with CO, and that they experience an average velocity change of ≈600 cm/s. A scattering kernel of exponential form is shown to be consistent with our results. We discuss the essential features of the estimated photon echo technique.

Observation of Dicke superradiance at 1.30 μm in atomic Tl vapor

Abstract Dicke superradiance in the 1.30-μm 7 2 P 1 2 → 7 2 S 1 2 transition in Tl vapor has been induced by a 379.1-nm pulsed dye laser. Superradiant delays of up to 12 nsec have been observed.

Observation and density dependence of the Raman echo in atomic thallium vapor

Abstract Working on the 6P 1 2 −6P 3 2 transition of atomic thallium vapor, we have observed Raman echoes generated by excitation and probe fields detuned from the 7S 1 2 intermediate state by up to 50 cm -1 . This constitutes the first time that echoes, generated by pure two-photon excitation, have been observed in an atomic system. The Raman echo intensity is found to increase roughly as the square of the thallium density at low densities, but at higher densities it peaks and subsequently declines. We suggest that two-photon absorption and loss of phase-matching resulting from excitation-pulse-induced population transfer are important in the high density degradation of the Raman echo signal.

Random access processing of optical memory by use of photon-echo interference effects

Photon-echo interference effects are used to manipulate the amplitude and polarization of a single echo generated by the read pulse in a long-lived stimulated echo pulse sequence. Interference is selective in time, frequency, and space, permitting modification of the multiplexed echo code.

Three-photon frequency shift on non-collinear excitation

The authors calculate the three-photon resonance absorption shift obtained with two non-collinear excitation beams of arbitrary orientation incident on an ensemble of collisionally broadened two-level atoms excited close to one-third of the resonance frequency. For counterpropagating beams the absorption resonance is narrow and shifted by the order of the linewidth to the violet. As the beams are angled away from the counterpropagating condition the shift increases, and if the angle approaches copropagation the shift becomes very large. When the shift exceeds the single-photon absorption linewidth by more than L/ lambda , the shifted line weakens and disappears, but a separate unshifted peak persists at copropagation. The third-harmonic generation response is more complicated. Except in the region where the beams are almost copropagating the shift in third-harmonic generation response follows the shift in the absorption response. In contrast to the absorption response the third-harmonic generation response increases as the excitation beams approach copropagation, then peaks, then diminishes, broadens and forms a complicated structure whose character is determined by phase matching.

Photon echo modulation effects in LaF3:Pr3+

Abstract Photon echo modulation effects have been observed in the 3 H 4 - 3 P 0 transition of LaF 3 :Pr 3+ in an applied magnetic field. Our results are interpreted as being due to the combined effect of the Pr nuclear Zeeman and hyperfine interaction.

Spatial modification of a Gaussian beam on reflection from a saturable absorber

We calculate the reflection coefficient of a dielectric-gas interface including the nonlinear local field, saturation, and self-reflected wave effects. We specialize to collisionally broadened gases with absorption lengths that are necessarily small compared with an optical wavelength and preclude the use of the slowly varying amplitude approximation. The dependence of the reflectivity on the intensity of the incoming field is revealed through the changes that it induces in the transverse profile of a reflected Gaussian beam. These changes derive principally from effective aperturing effects in amplitude and phase.

Dynamic Lorentz shift revealed via non-linear multiwave excitation

The authors propose a method to detect and study the non-linear dynamic Lorentz shift in an atomic vapour by applying a controlled intense fixed frequency optical field detuned from resonance and then measuring the spectral reflectivity of a weak excitation which is scanned through the atomic resonance. Even though the nearby pump is intense the reflectivity response is not power broadened, has a Lorentzian response and exhibits a non-linear shift from which the dynamic Lorentz shift can be extracted.