Power resonances in a Raman gas laser

The observation of a new type of resonance due to double-quantum transitions in the standing-wave field of a Raman gas laser is reported. A resonance dip with a width equal to that of the optically forbidden transition was experimentally detected in the output-vs-timing curve of a Raman Ne laser (λ=1.15 m) upon pumping by radiation of a He−Ne laser at 1.52 m. The theory presented shows that the resonance arises in the third order of perturbation theory when in resonant SRS the line is inhomogeneously broadened. The resonance can be considered as resulting from the overlap of dips in the velocity distribution of the nonlinear polarization induced by the standing laser wave.     

Interference of atom,and atomic spatial lattices in light fields

A scheme is proposed to observe interference of atoms by using a weakly coherent atomic beam scattered at two standing light waves. It is shown that atoms can transfer spatial coherence over rather large distances.     

Non-linear ramsey resonance in the optical region

The interaction of gas particles with three separated light fields has been considered. It has been shown that a resonance with the width equal to the reciprocal transit time appears in such a system. The resonance is due to coherence conservation and change of distribution of a number of particles by nonlinear interaction with the fields. Its properties are close to the Ramsey resonance in the microwave range. This new type of resonance may have a relative width of 10⁻¹¹ to 10⁻¹².     

The SRS line-shaped nonlinear resonance in consideration of flight effects

We investigate the problem of nonlinear interaction of a gas of three-level atoms with the field of standing waves in the situation where the atomic free path length at the initial and final metastable levels is comparable with the transverse dimensions of the field. The standing waves are resonant to adjacent Doppler-broadened transitions. The case of fields of Gaussian profile is analysed. It has been shown that in the limiting case of large free path length the nonlinear resonance width is of the order of the inverse time of flight of an atom in the field. The first and second derivatives of resonance with respect to frequency are considered. It has been shown that in the situation of flight they contain narrow resonant structures with a width of the order of a homogeneous width of the forbidden transition between metastable levels.     

Raman scattering resonances in separated fields

The effects in separated standing-wave fields that are resonant to adjacent Doppler-broadened transitions of many-level atoms are studied. It is shown that due to coherent transfer, at large distances, of polarization on a forbidden transition between the initial and final metastable levels of atoms in a gas, light emission arises at combination frequencies. It is also shown that a resonance with the width reciprocal to the time of flight between separated fields is available in the Raman scattering and absorption line shapes.     

Magnetic-grating free-induction decay and magnetic-grating echo using ultrafast excitation pulses

The interaction of atoms with ultrafast, counterpropagating optical fields is considered. The magnetic degeneracy and hyperfine splitting of the atomic levels are included in the calculations, which are carried out for arbitrary polarizations of the incident fields. The counterpropagating fields produce spatial harmonics in the ground state density matrix (gratings) which can be monitored by backscattering of a traveling wave probe pulse. Two types of excitation schemes are analyzed. The Magnetic-Grating Free-Induction Decay (MGFID) consists of excitation with a single counterpropagating wave field, while the Magnetic-Grating Echo (MGE) involves excitation by two counterpropagating wave fields, separated in time by T. The atomic response to the probe pulse is calculated in lowest-order perturbation theory for atoms cooled below the Doppler limit of laser cooling. Both the MGFID and MGE signals consist of pulses having a duration of order of the excited state lifetime, modulated at frequencies corresponding to the various hyperfine transitions. As a function of the delay between pulses, the signals oscillate at frequencies determined by the ground state hyperfine splittings. General expressions for the MGFID and MGE signals are derived and specific results are presented for the D₂ line in Na.     

Shock shells in Coulomb explosions of nanoclusters

We predict that Coulomb explosion of a nanoscale cluster, which is ionized by high-intensity laser radiation and has a naturally occurring spatial density profile, will invariably produce shock waves. In most typical situations, two shocks, a leading and a trailing one, form a shock shell that eventually encompasses the entire cluster. Being the first example of shock waves on the nanometer scale, this phenomenon promises interesting effects and applications, including high-rate nuclear reactions inside each individual cluster.     

A classical model of the photon echo

An observation and the theory of a nonlinear response in the ensemble of nonlinear classical oscillators excited by two field pulses — similar to the phenomenon of a photon echo in optics — are reported. It has been shown that an echo arises in any ensemble with an inhomogeneously broadened line regardless of the type of interaction with a field (classical or quantum). New peculiarities appear during the determinate distribution of frequencies in the ensemble. On the one hand, an echo pulse is observed with a relatively small (about 100) number of oscillatorsN, on the other, new pulses spaced at a distance that is proportional toN arise in the nonlinear response.     

The resonance of two-photon absorption in separated optical fields

A beam of molecules interacting with two space-separated light standing waves of light is considered. It is shown that a resonance of two-photon absorption is predicted. The width of the resonance is equal to the reciprocal of the time of flight between the waves.