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Using quantum coherence effects, we have developed a new technique of detection of motion of single atoms or ions in an optical cavity. We have theoretically demonstrated that the presence of a sin...

We present a study of the interaction of coherent field effects on population of two bound atomic states of a dense atomic gas interacting in a cooperative regime. We provide a theoretical description of this phenomenon using density matrix equations. We discuss the implications and applications of the present studies to quantum amplification by superradiant emission of radiation action. A classical model is developed to gain physical insights into qaser physics.

We consider an opto-mechanical effect that is related to the appearance of additional optical phase due to motion of an ultra-dispersive medium, the enhanced Fizeau effect. We have theoretically shown that the enhanced Fizeau effect on a single atom in a cavity can be observed. It has been shown that the change of phase is sensitive to the mechanical motion and can be applied to measurement of possible displacements as small as cm Hz. One of application can be the detection of weak forces exerted on a single atom.

Quantum optics with X-rays has long been a somewhat exotic activity, but it is now rapidly becoming relevant as precision x-ray optics and novel X-ray light sources, and high-intensity lasers are becoming available. This article gives an overview of the current state of the field and an outlook to future prospects.

Excitation of induced coherent Smith–Purcell (SP) radiation by relativistic magnetized electron beam in the absence of the resonator is considered within the framework of the dispersion equation. We have found that the dispersion equation for the SP instability is a quadratic equation for frequency. The first-step approximation for solution of the dispersion equation, giving the SP-spectrum of frequency, corresponds to the mirror boundary case, when the electron beam propagates above a plane metal surface (mirror). It was found that the conditions for both the Thompson and the Raman regimes of excitation do not depend on beam current and depend on the height of the beam above the grating surface. The growth rate of the instability in both cases is proportional to the square root of the electron beam current. No feedback is needed to provide the coherent emission.

We have found an analytical solution of the 3D stationary Schrodinger equation for any arbitrary potential. The solution has been obtained by transforming the Schrodinger equation to the generalized Ricatti equation, and it has the form of Huygens’ principle for matter waves. We have shown that the solution is more accurate than the JWKB approximation. We discuss possible applications of the solution to molecular dynamics and dynamics of charges in nanostructures.

We study the dynamics of a two-level system driven by a strong off-resonant electromagnetic field. We derive an analytical solution for arbitrary pulse shape and discuss possible applications of the results obtained.

Motivated by the recent experiment [Sautenkov, V.A.; Rostovtsev, Yu.V.; Scully, M.O. Phys. Rev. A 2005, 72, 065801], we study the field intensity fluctuations due to interaction between a laser with a finite bandwidth and a dense atomic medium. The intensity–intensity cross-correlation of two orthogonal, circular polarized beams can be controlled by the applied external magnetic field. A smooth transition from perfect correlations to anti-correlations (at zero delay time) of the outgoing beams is observed.

We study population transfer in a two-level system interacting with a strong off-resonant electromagnetic field. We show that the effects of tunneling in an electric field enhances the probability of excitation. We discuss the possible applications of results obtained to the generation of XUV radiation.

An analytical expression is received for the effective interaction potential of a fast charged particle with the ionic crystal CsCl near the direction of axis ⟨100⟩ as a function of the temperature of the medium. By numerical analysis it is shown that the effective potential of axial channeling of positrons along the axis ⟨100⟩ of negatively charged Cl− ions practically doesn't depend on temperature of the media. The wavefunction and the energy spectrum of the localized state are investigated, and the possibility is proved for the formation of metastable, two-dimensional relativistic positron systems or the positron atoms (PA), i.e. the bound state of a positron in the present case with a negatively charged axis of ions. The problem of one-photon decay of PA is investigated. The possibilities of stimulation of resonant transitions between quantum states of PA by the external hypersound are investigated in detail.

We have studied a time response of electromagnetically induced transparency (EIT) in a rubidium vapor to a rapid variation of optical phase. We have observed a very fast growth of the absorption when the phase of the optical field has been abruptly changed, followed by a slow return to the level of steady-state absorption. The recovery time decreases with increasing optical power. A simple theoretical analysis shows that under our experimental conditions the low power limit of the recovery time is determined by the ground relaxation time. In our case it is defined by a time-of-flight of rubidium atoms through laser beam. The obtained value of the ground state relaxation time is in a good agreement with result of direct measurements by ‘relaxation in the dark’ method. Our technique based on phase dynamics in EIT can be used for investigation of the ground state relaxation and the fast control of EIT.

We have studied phase dynamics in EIT in a dense rubidium vapor. We have observed a very fast growth of the absorption when the phase of the optical field was abruptly changed, followed by a slow return to the steady state absorption. Then the transmission was slowly restored to stationary magnitude. The recovery time is on the order of the transit time of the atom flying through the laser beam and decreases with increasing optical power. The fast variation of the transparency is proportional to the phase deviation. The obtained result can be used for the fast control of EIT, for example, in an optical switch.

We find that intense short pulses of XUV radiation can be produced by cooperative spontaneous emission from visible or IR laser pulses driving atoms or ions. The process depends on the generation and utilization of atomic coherence as is the case in lasing without inversion. However, the radiation process is not stimulated emission, but is rather cooperative spontaneous emission in the sense of Dicke. More precisely, the many atom mathematics of superradiance has much in common with coherent anti-Stokes Raman scattering. †It is a pleasure to dedicate this article to Professor Lorenzo Narducci: scientist, scholar, savant. All who were touched by him were enriched. The generation of Raman coherence is considered from the perspectives of multi-photon excitation and breaking of adiabaticity. In particular, we find that the advent of an ultrashort (e.g. single cycle) pulse rewards rethinking of conventional (nanosecond) nonlinear optics with new insights.

We study population transfer in a three-level system interacting with a strong off-resonant electromagnetic field consisting of radiation with two optical frequencies. We show that the presence of the second frequency broadens multi-photon resonances and even for higher than 3-photon resonances the probability of excitation weakly depends on optical frequency. We discuss possible applications of results obtained for generation of XUV radiation.

We have studied a scheme of lasing without inversion (LWI) that uses the Pauli exclusion principle. We perform simulations to demonstrate the gain at 58 nm using parameters for 3He. The usage of the Pauli principle allows us to meet the necessary condition for LWI and provides also the efficient control of the coupling between X-ray radiation and atomic system. This approach can be extended to other atoms and ions to obtain lasing at shorter wavelengths.

We show that the interference effects (similar to electromagnetically induced transparency, which was widely studied earlier in electronic transitions in optics) may appear in γ-radiation at nuclear transitions under the condition of nuclear level anticrossing. We demonstrate it also experimentally in optically thin samples of FeCO3.

We experimentally and theoretically study Raman scattering in rubidium (Rb) dimers. We observe the optical lines resulting from Raman scattering and demonstrate Raman amplification in the backward direction. A theoretical model has been developed to explain experimental the results.

We study nuclear elastic forward scattering of synchrotron radiation. In a simple model, we show that suppression of nuclear excitation by synchrotron radiation as well as nuclear elastic forward scattering are possible due to the formation of nuclear coherent population trapping. We consider a nucleus with ground- and excited-state nuclear momenta , , respectively. We demonstrate that nuclear coherent population trapping can be achieved for random phases of pulses in synchrotron radiation.

We combine techniques of high-resolution absorption spectroscopy and laser-induced fluorescence spectroscopy to study electric-dipole allowed Λ-transitions in rubidium molecules. By using a tunable diode laser, we excite several selected transitions between rotational sublevels of ground and excited electronic states and record the fluorescence spectral lines. We discuss the possibility of creating a rubidium laser based on the observed molecular transitions.

We conduct a numerical study of the possibility of using the `magic-angle' technique to suppress inhomogeneous broadening of Mossbauer spectra. We use the Floquet-state perturbation theory for the rf modulation of the Mossbauer resonance, which was adjusted to suit our purpose. A system of two nuclei of 57Fe coupled by the dipole–dipole interaction is considered. The analysis here completes studies started in 2004, by including the dipole–dipole interaction between one nucleus in the ground state and the other in the excited state. We show that partial suppression of inhomogeneous broadening remains possible.

We show that it is possible to improve the efficiency of a laser system by adding a classical heat engine cycle to the laser gas which can remove both thermal and vibrational energy from the gas. Rapid pulsed CO 2 laser-gas expansion cycle engine and a continuous CO 2 laser-Brayton cycle engine are analysed to determine practicality. Combined laser-mechanical efficiencies can approach 80% for operational systems.

Mossbauer spectra under the presence of inhomogeneous broadening due to dipole-dipole interaction have been studied. Floquet state perturbation theory has been used for the density matrix analysis of a simple model. The parameters of 57Fe are used for simulations. We have shown that a spinning magnetic field can eliminate inhomogeneous broadening. Application to Mossbauer spectroscopy is discussed.

We develop a theoretical approach and perform simulations of coherent anti-Stokes Raman scattering (CARS) with ultrashort laser pulses. The signal is generated by biomolecules having subpicosecond dephasing times, from femtosecond pulses on exact resonance with the molecular transitions. All propagation effects are explicitly accounted for, including pump depletion, Raman amplification, parametric generation and pulse reshaping. Our model predicts that a measurable CARS signal can be generated by the dipicolinic acid biomolecule under realistic conditions.

Robust control of atomic coherence and population transfer among Zeeman sublevels in the ground states of rubidium atom is investigated using adiabatic rapid passage in a nanosecond time scale, which is smaller than the lifetime of first excited Rb. It is shown that a slight change in the pump pulse time delay relative to the Stokes pulse leads to a significant modification of atomic coherence and population transfer, consequently having remarkable impacts on the generation of coherent anti-Stokes Raman scattering (CARS) signal and probe pulse absorption. This coherent control of quantum state and population is presented by numerical simulations based on self-consistent set of density matrix equations and Maxwell equations as well as experimental demonstration in rubidium atom with different atomic densities. Experimental observations are in good agreement with numerical calculations.

We report, in this paper, a narrow dip of electromagnetically induced absorption inside the optical pumping window by the interaction of two coherent laser fields with a quasi-degenerate two-level open atomic system in inhomogeneously broadened Rb vapour. The effect arises from optical pumping and laser-induced atomic multilevel Zeeman sublevels in the same ground state. The numerical simulation for a N-type four-level system shows good agreement with experimental observation.

We study the behaviour of the group velocity of light under conditions of electromagnetically induced transparency (EIT) in a Doppler broadened medium. Specifically, we show how the group delay (or group velocity) of probe and generated Stokes fields depends on the one-photon detuning of drive and probe fields. We find that for atoms in a buffer gas the group velocity decreases with positive one-photon detuning of the drive fields, and increases when the fields are red detuned. This dependence is counterintuitive to what would be expected if the one-photon detuning resulted in an interaction of the light with the resonant velocity subgroup.

A ‘phased’ optical klystron drift region developed to obtain free-electron lasing (FEL) without inversion in the small-gain small-signal regime is here applied to the high-gain regime. Numerical simulations show improvement in the gain and the tolerance to electron beam energy spread compared to conventional FEL. Longitudinal phase space dynamics has been studied to show the effect of the drift region on the electron beam.

We study the behavior of the group velocity of light under conditions of electromagnetically induced transparency (EIT) in a Doppler broadened medium. Specifically, we show how the group delay (or group velocity) of probe and generated Stokes fields depends on the one-photon detuning of drive and probe fields. We find that for atoms in a buffer gas the group velocity decreases with positive one-photon detuning of the drive fields, and increases when the fields are red detuned. This dependence is counter-intuitive to what would be expected if the one-photon detuning resulted in an interaction of the light with the resonant velocity subgroup.

We study both theoretically and experimentally three-photon electromagnetically induced transparency and electromagnetically induced absorption resonances in inhomogeneously broadened 85 Rb atomic vapour driven by probe and drive laser radiations. We observe narrow Doppler-free absorption as well as transmission resonances for the probe field when the driving laser field is redshifted from the D1 or D2 lines of 85Rb; the frequency difference between the drive and probe fields is equal to the hyperfine splitting of the ground state of the atoms, and the probe field is tuned to the centre of the Doppler broadened atomic transition. We theoretically study the spectroscopic effect in both homogeneously and inhomogeneously broadened media. Our numerical simulations are in good agreement with the experimental results.

We consider a new way to trap light pulses inside a gaseous medium by using additional electromagnetic fields. The drive field controls the transparency and the dispersion of the medium. Applied auxiliary fields provide additional control on the propagation of the probe pulse via the dragging effect resulting from the population redistribution between hyperfine levels of different velocity groups. The density matrix calculation is performed to prove that these effects are experimentally feasible.

The laser-induced line narrowing effect in Doppler broadened systems was discovered thirty years ago. We have revisited this effect to determine its role for dense gases where recent experimental studies have found many intriguing atomic coherence effects. Using the density matrix approach, we study the width of electromagnetically induced transparency under different regimes of broadening.

We report transmission linewidths for a weak anti-Stokes component and generated Stokes component during resonant four-wave mixing in atomic Rb vapour. We consistently observe larger linewidth of the generated field relative to the input field.

Spectroscopy of the Doppler broadened Rb atomic vapour coherently driven by two coupling fields is presented. Double dark resonances have been observed in different geometries of the coupling fields. A simple four-level model explains the basic counter-intuitive features of experimental spectra. The eigenvalues of the atom-field system distinguishing between the various geometries clarify the physics.