Two-frequency Laser Radiation Research Articles

Influence of collisions on the effect of electromagnetic-induced transparency in cells of finite sizes with anti-relaxation coating of walls

Based on the semiclassical theory of the interaction of two-frequency laser radiation with a resonant atomic medium, an analytical expression is obtained that describes the form of resonances of electromagnetically induced transparency detected in a cell with a finite direction in the longitudinal laser beam direction with an anti-relaxation coating of walls, taking into account the motion of atoms and collisions with walls. The following types of reflection from walls are considered: diffuse, specular, and specular-incoherent. It is found that in a number of cases the diffuse type of reflection exhibits the properties of a mirror-incoherent one. It is also shown that the nondegeneracy of the excited state in a number of cases significantly changes the shape of the transparency resonance. Keywords: Electromagnetically induced transparency, Gas cell, anti-relaxation coating, diffuse reflection, specular reflection, specular-incoherent reflection.

Влияние столкновений на характер эффекта электромагнитно-индуцированной прозрачности в ячейках конечных размером с антирелаксационным покрытием стенок

Based on the semiclassical theory of the interaction of two-frequency laser radiation with a resonant atomic medium, an analytical expression is obtained that describes the form of resonances of electromagnetically induced transparency detected in a cell with a finite direction in the longitudinal laser beam direction with an anti-relaxation coating of walls, taking into account the motion of atoms and collisions with walls. The following types of reflection from walls are considered: diffuse, specular, and specular-incoherent. It is found that in a number of cases the diffuse type of reflection exhibits the properties of a mirror-incoherent one. It is also shown that the nondegeneracy of the excited state in a number of cases significantly changes the shape of the transparency resonance.

Autobalanced spectroscopy of CPT resonance in an optically dense atomic ensemble

We investigate the influence of optical thickness on the coherent population trapping (CPT) resonance interrogated by the autobalanced Ramsey method as well as by the method of combined error signals (CESs). We analyze sensitivity of the CPT resonance to the light shift of the etalon transition for the microwave quantum frequency standards based on cold or hot atomic ensembles. When the CPT resonance is excited, two-frequency laser radiation can be significantly absorbed at the atomic transitions of the optical range. The effects of absorption and phase incursion lead to additional shift of the reference resonance. This is an additional factor that degrades the accuracy of the frequency standards because this additional shift can vary with intensity and temperature fluctuations. It was shown that the CES method is more robust in an optically dense medium than is the autobalanced Ramsey method, but it also undergoes the light shift. We found that by choosing the normalization factor of the CES method it is possible to suppress the light shift for a certain density of the medium or suppress its sensitivity to temperature fluctuations.

Excitation of high-intensity terahertz surface waves under action of two-frequency laser radiation

The excitation of terahertz (THz) surface mode at oblique incidence of two-frequency laser radiation on semi-bounded plasma is studied. It is shown that if frequency difference of laser fields coincides with the surface eigenmode frequency, the significant increase surface wave (SW) field occurs. It is found that additional amplification of SW field occurs when the s- and p-polarized laser radiation is incident at the angle of total reflection. The SW energy flux density increases most significantly for p-polarized laser radiation when it is incident at the angle of total reflection on the near-critical plasma with rare electron collisions. It is shown that in this case the SW energy flux density can significantly exceed the laser intensity.

Excitation of Low-Frequency Surface Modes in the Plasma Layer Under the Action of Two-Frequency Laser Radiation

We construct the theory of generation of low-frequency surface eigenmodes in a rarefied plasma layer under the action of two-frequency laser radiation. We show that a significant increase in the energy of the plasma-layer low-frequency eigenmode occurs under resonance conditions, where the frequency of the mode coincides with the difference in laser frequencies. We establish that under the resonance conditions the energy flux density carried by the low-frequency eigenmode can be comparable to the laser-radiation intensity.

High contrast resonances of the coherent population trapping on sublevels of the ground atomic term

We have detected and analyzed narrow, high contrast coherent population trapping resonances, which appear in transmission of the probe monochromatic light beam under action of the counterpropagating two-frequency laser radiation, on example of the nonclosed three level {\Lambda}-system formed by spectral components of the Doppler broadened D2 line of cesium atoms (in the cell with the rarefied Cs vapor). These nontrivial resonances are determined directly by the trapped atomic population on the definite lower level of the {\Lambda}-system and may be used in atomic frequency standards, sensitive magnetometers and in ultrahigh resolution laser spectroscopy of atoms and molecules.

Identification of overlapping optical lines in molecular spectra by means of the coherent population trapping of quantum levels

A new method of molecular beam spectroscopy with the ultrahigh resolution is theoretically suggested. This method is based on the phenomenon of the coherent population trapping of molecular levels and allows the identification of the overlapping optical lines in complex spectra (typical for polyatomic molecules), even when frequency intervals between the centers of given lines are less than their natural line widths. The theoretical analysis is carried out on the basis of the Schrodinger equation for the three-level molecular A-system interacting with the two-frequency laser radiation. The conditions of the practical realization and possible applications of the suggested spectroscopy method are discussed.

A New Method of Dark Resonance Excitation on D[sub 2] Line in [sup 87]Rb Vapor

A new method based on optical pumping is proposed for increasing the parameters of dark resonance excitation on D2 line in 87Rb vapor. The pumping is provided by linearly polarized two-frequency laser radiation propagating in the direction perpendicular to the probing field directed along the cell with atomic rubidium vapor. This method significantly improves the dark resonance parameters as compared to the case of pumping by a circularly polarized field. Qualitative considerations are confirmed by the results of numerical calculations.

Application of two-frequency laser radiation for transfer of length measurements in the large-length range

We consider transfer of a length unit, the meter, by using a wave measure of length for range finding with the high-accuracy UVT 5-84 instrument. We present a scheme for transfer of measurement units using two-frequency laser radiation.

Resonant Λ medium as a converter of the laser radiation frequency

A theoretical investigation is made of the propagation of two-frequency laser radiation in an optically dense Λ medium in the presence of an rf field which is in resonance with a transition between the lower levels of a Λ-like system of an atom. It is shown that, depending on the phase and amplitude of the rf field and on the initial phases and intensities of the laser waves, one laser wave may be amplified at the expense of the energy of the other wave, or coherent bleaching of the medium (propagation of both waves without intensity losses) may take place.

Generation of microwave current pulses in the erosion plasma of a metallic target by two-frequency laser radiation

When IR laser radiation that is intensity-modulated at a frequency of 1.1 GHz is incident on a conducting target in a rarified gas at a pressure of 0.1 torr, microwave modulation of the current pulses generated in the erosion plasma is observed. A microwave signal with a voltage amplitude of 2 V is obtained at a laser intensity of 100 GW/cm2. The efficiency of the conversion of laser energy to the microwave band at an intensity of 10 GW/cm2 is 2.5 ? 10?7.

Erratum: Optical pressure force in travelling and standing light waves during excitation of a multilevel atom by two-frequency laser radiation [Sov. J. Quantum Electron. 16, 1487–1491 (November 1986)

Erratum: Optical pressure force in travelling and standing light waves during excitation of a multilevel atom by two-frequency laser radiation [Sov. J. Quantum Electron. 16, 1487–1491 (November 1986)

Optical pressure force in traveling and standing light waves during excitation of a multilevel atom by two-frequency laser radiation

An experimental investigation was made of the behavior of the optical pressure force created by the interaction of a two-frequency laser field with a sodium atom in traveling and standing light waves. It was found that the optical pressure forces due to a traveling wave were quite different for a two-level atom and an atom of sodium. In a standing wave field the motion of atoms was governed mainly by pulsed diffusion.

Nonadiabatic transitions in a three-level system subjected to a laser radiation field with a smoothly varying frequency

Explicit expressions are obtained for the probabilities of transitions in a three-level system subjected to two-frequency laser radiation. The radiation or transition frequencies vary smoothly with time, passing through a resonance. The results obtained generalize the Landau–Zener solution to the case of three crossing levels, and they can be used to describe a number of physical phenomena.