Bichromatic Radiation Research Articles

Quantum phase gating with semiconductor quantum dots in a microcavity

We propose a scheme to carry out quantum phase gate in one step by bichromatic radiation method with semiconductor quantum dots (QDs) embedded in a single mode microcavity. The spin degrees of freedom of the only excess conduction band electron are employed as qubits and excitonic states are used as auxiliary states. The nearest-neighbor coupling is not required because the cavity mode plays the role of data bus. We show how to perform quantum computing with properly tailored laser pulses and Pauli-blocking effect, without exciting the cavity mode.

Phase control of external photoeffect in a bichromatic laser field

The photocurrent from a metal surface under the action of bichromatic radiation is calculated as a function of the phase shift between monochromatic components (bichromatic phase). The dependences of the external photoeffect on the bichromatic phase as well as on parameters of the surface potential barrier are obtained, which could be the physical basis for a new phase method of optical surface diagnostics.

On The “Nonresonance” Parametric Cyclotron Radiation

We study the effect of amplification of coherent bichromatic radiation due to its cyclotron parametric interaction with a modulated ensemble of classical electron oscillators. The mechanism of energy exchange between the radiation and the electrons in the absence of partial synchronism of the waves and particles is analyzed. The features of the energy exchange in the course of interaction of the waves with relativistic and nonrelativistic particles are pointed out.

Bichromatic pulsed source in the visible and infrared

A source of bichromatic coherent radiation is described with independent tunability in wavelength, energy and pulse duration. The system is able to deliver pulses in the visible to infrared region with possible extension into the ultraviolet. Pulse durations can be tailored to be from 15 ps to 310 fs with collimated beam fluences of several mJ/cm2.

Quantum computing in cavity QED with cold trapped ions by bichromatic radiation

In the system with ions confined both in a linear trap and in a high-Q single mode cavity, we present a simple quantum computing scheme by means of lasers and quantized cavity field, based on a previous proposal with bichromatic radiation [Phys. Rev. Lett. 82, 1971 (1999)]. The controlled-NOT gate operation can be performed by only three operations and it is independent of motional states of ions. Experimental feasibility for achieving our scheme is discussed.

On the Theory of “Inversionless” Free-Electron Maser

We develop a linear theory of cyclotron parametric instability in systems that are classical analogs of quantum inversionless lasers. Interaction of bichromatic radiation with an ensemble of classical electron oscillators having a modulated distribution function is considered taking into account that the cyclotron-resonance conditions is valid both for each of the two spectral components at high harmonics and for their beat wave. It is shown that the ballistic restructuring of the modulated fraction of the electrons leads to stabilization of the instability. In this case, a peculiar nonreciprocal regime of the parametric particle-field interaction is realized in which the evolution of the high-frequency wave is independent of the low-frequency mode, though the former wave affects the behavior of the latter one.

Collinear interaction of bichromatic radiation with one acoustic wave in biaxial crystals

The regime of collinear interaction of bichromatic optical radiation in biaxial crystals is considered. It is shown that the possibility of the realization of such an interaction is due to dispersion of the optical axes in a biaxial crystal.

Double refraction in coherent media

A new effect of double refraction in a coherent medium with a double-Λ scheme of excitation is analysed theoretically. It arises if usual phase conditions on coherent population trapping in a quantum system with closed interaction contour are satisfied. The value of the refractive index of such a medium is different for matched and antimatched (by amplitude) parts of a bichromatic laser radiation. Therefore the matched part can be separated spatially from the antimatched one using the optically thin coherent medium as a birefringent prism. A possible scheme for experimental observation of this effect is discussed.

QUANTUM OPTICS WITH NUCLEAR GAMMA RADIATION

Some features of quantum optics related to inversionless amplification are translated to nuclear systems. Nuclei and nuclear transitions differ in several ways from atomic systems: gamma radiation has a much shorter wavelength (of the order of lattice-distances), nuclear transitions are many orders of magnitude weaker than atomic ones (making nuclear pumping extremely hard), no coherent gamma-ray sources are available to produce bichromatic gamma radiation. All this makes it very hard to merely translate quantum optical results to nuclear systems. We show that under very specific conditions destructive quantum interferences can occur in the nuclear absorption probability, while the stimulated emission probability is not affected. Nuclear level mixing plays a crucial role in this.

Multiply Charged Negative Ions of Hydrogen Induced by Superintense Laser Fields.

Using the high-frequency Floquet theory of laser-atom interactions we predict that in superintense fields a proton can bind more than two electrons. For linear polarization, a self-consistent solution of the structure equation shows that H{sup 2{minus}} becomes bound for {alpha}{sub 0}=155 a.u. The fields and frequencies needed for binding H{sup 2{minus}} are within reach of lasers under construction. By choosing appropriately polarized bichromatic radiation, the production of more highly charged negative ions also lies within experimental reach. The ions are (adiabatically) stabilized against ionization, from their very appearance. {copyright} {ital 1996 The American Physical Society.}

Relaxation of the optical density of glass modulated with bichromatic radiation

Exposure of oxide glass to two coherent light beams with different frequencies v and 2v leads to the buildup of spatial index gratings in the glass. The kinetics of the writing and relaxation of the gratings is investigated. Illumination with one beam or a background illumination of the sample accelerates the relaxation process; this acceleration is due to the appreciable photoconductivity of the glass. The diffraction is found to reach a residual self-maintaining level when a grating is illuminated continuously with a beam at the fundamental frequency. The results are analyzed on the basis of a model that includes the coherent photogalvanic current, the accumulation of a grating of nonuniform charges under the action of this current, and the back-effect of the static field, via electrooptic effects, on the propagation of the beams. It is shown that an optical instability of the photoinduced index gratings exists in the glass. © 1996 American Institute of Physics. @S00213640~96!00503-3#

Quasienergy spectrum of a two-level atom in the field of high-intensity modulated radiation

An asymptotic method is proposed for the determination of quasienergy levels of an atom in the field of modulated optical radiation. A comparison of the asymptotic and exact solutions is used to show that the range of validity of the new method is considerably wider than those of the known asymptotic methods. An analysis is made of the shifts of the quasienergy levels of an atom under the influence of bichromatic radiation and of a periodic pulse sequence. A modulation method is proposed for the attainment of Doppler-free resonances in gases.

Role of multiphoton processes in four-photon scattering using high-intensity bichromatic pumping

A theoretical analysis is made of the action of high-intensity bichromatic pump radiation on a system of vibrational–rotational molecular levels. The effective Hamiltonian approximation is used to reduce the problem to the solution of kinetic equations for the density matrix with a periodic external perturbation. These can be solved by adopting a basis of quasienergy states. The Raman susceptibility profile is obtained and investigated for an isolated vibrational resonance. It is shown that any change in the polarizability under excitation can be determined from the dependence of the population difference on the pump and scattered radiation intensities.