Optics and Spectroscopy (v.109, #1)

Sixth seminar in memory of D. N. Klyshko at Moscow State University by S. P. Kulik; A. N. Penin; M. V. Chekhova (1-1).

The spectral dynamics of a two-component pulse propagating at an arbitrary angle to the optical axis of a uniaxial crystal is analytically studied. Frequencies for which spectral densities of components are maximal are found from asymptotic solutions. Contributions of quadratic and cubic nonlinearities into the signal spectrum dynamics are analyzed.

We demonstrate the possibility of an efficient generation of terahertz radiation under optical rectification in a uniaxial crystal containing impurities with resonance two-level quantum transitions. The group velocity of an optical pulse entering the regime of self-induced transparency decreases to the value of phase velocity of the terahertz radiation, which results in phase matching of long- and short-wavelength waves. The terahertz generation is accompanied by strong self-modulation of the optical pulse. Two-component soliton-like structures can be formed at long distances accompanied by spectral red shift of the optical component.

A complete system of solutions of the equation describing the parametric excitation of an oscillator is presented. This system makes it possible to take into account losses in a parametrically excited oscillator in terms of the perturbation theory. It is shown that, although the oscillator losses are small (the relative spectral width of a typical laser cavity is 10−8), they limit the achievable squeezing coefficients by values on the order of ten. At present, the progress in resonator technique allows one to achieve relative spectral widths on the order of 10−11–10−12. Therefore, it can be expected to achieve squeezing coefficients on the order of 103.

Generation of polarization-squeezed light in doped resonant media by G. A. Burmakin; M. Yu. Gubin; A. V. Prokhorov; S. M. Arakelyan (19-25).
The cross-interaction effects for a two-mode light pulse in an optical matrix doped with atoms that are resonant with the light in the presence of two control optical pump pulses (M scheme) have been analyzed. The fundamental possibility of effective generation of polarization-squeezed light in this system at a simultaneous nonlinear amplification of the probe field is shown. The optimal conditions for generating polarization-squeezed light in a doped optical fiber are found for different problem parameters.

Relaxation in an entangled thermostat by V. N. Gorbachev; A. I. Trubilko (26-31).
A generalized Lindblad equation is derived that describes the relaxation of two systems of an arbitrary physical nature in an entangled thermostat. The relaxation of an atom and a mode of the electromagnetic field selected by a high-Q cavity is considered as an example. Using the introduced collective operators for an atom and a mode, it is shown that the entangled state of the thermostat can lead to the coherent and squeezed state of the atom and the mode.

A method of writing and reading single-photon states of light in quantum memory devices whose information carriers are optically thin resonant media placed in a cavity is developed. It is shown that, using a tunable cavity, it is possible to write and reproduce Gaussian single-photon wave packets with an efficiency close to unity. The possibility of using this method for the transformation of the time shape of single photons generated in the cavity-enhanced spontaneous parametric down conversion regime is analyzed.

The spontaneous emission from an atomic ensemble localized in a microcavity with the participation of microcavity photons and an external broadband quantized electromagnetic field at the Raman resonance of photons with an optically forbidden (two-photon) atomic transition has been studied. The average spontaneous decay intensity has been calculated for simple cases. It is shown that the dynamics of spontaneous emission from this atomic ensemble differs generally from the conventional superradiance (spontaneous emission of an atomic ensemble at a one-photon optically allowed transition from excited to the ground state. When the atomic ensemble is strongly excited, the delay times and the emission pulse shape differ significantly. The parameter ranges where the spontaneous emission from the atomic ensemble under consideration at a two-photon Raman transition can be described as conventional superradiance with renormalized parameters are found. In the case of single excitation the photon emission probability depends on the number of photons and atoms in the microcavity.

We report the results of a detailed study of the Brownian noise of an interferometric coating, which is the principal factor that limits the sensitivity of laser gravitational antennas. It is established that the noise level is lower than previously anticipated due to the influence of interference that takes place inside the coating. Optimizing a coating with the goal of decreasing the Brownian noise is attempted.

We demonstrate the importance of using the method of superposition for the precise calculation of frequencies and forms of axially symmetric elastic modes of test masses in gravitational antennas LIGO for detailed analysis of the effect of parametric oscillatory instability. The method allows one to construct analytical expressions for particular solutions to the medium equations of motion in cylindrical coordinates, which allow one to satisfy all zero boundary conditions. The obtained results allow considerably more reliable methods (as compared to meshing methods) to be used for predicting the number of combinations of optical and elastic modes that lead to the undesirable effect of the parametric oscillatory instability.

Laser-induced optical activity in range of Rydberg autoionizing states of xenon by E. V. Gryzlova; A. N. Grum-Grzhimailo; A. I. Magunov; S. I. Strakhova (59-65).
Optical activity of xenon atoms in the vacuum UV range induced by circularly polarized laser light is studied theoretically. The optical activity arises in the vicinity of the autoionizing state 5p 5(2 P 1/2)8s′ $$ left[ {frac{1} {2}} ight]_1 $$ as a result of its coupling via the laser field with the discrete state 5p 5(2 P 3/2)7p $$ left[ {frac{1} {2}} ight]_1 $$ . Polarization variations of the vacuum UV radiation upon its propagation through the atomic medium are calculated, and the possibility of controlling this polarization is discussed. Manifestations of nonresonant coupling of the discrete state with the broad autoionizing state 5p 5(2 P 1/2)6d′ $$ left[ {frac{1} {2}} ight]_1 $$ induced by the overlap of the Rydberg autoionizing series in xenon are studied.

Geometric properties of correlated exponential basis functions for n-particle Coulomb systems are studied. Using a system of model Schrödinger equations, the relations between the average values of Coulomb interaction energies of pairs of the particles and average values of cosines of the angles of mutual tilt of interparticle bonds are derived. The use of these relations significantly simplifies calculations of the energy operator matrix of many-particle systems by reducing them to evaluation of the Coulomb and normalization integrals. Geometric inequalities are established that allow one to estimate the many-particle Coulomb interaction integrals that are hard to evaluate. The results obtained can be used in calculations of atomic-molecular systems.

In terms of the adiabatic theory of interactions, we consider the results of the theoretical estimation of the rate constants K ST of the nonradiative intersystem crossing conversion S 1(ππ*) ⇝ T 1 S (ππ*) for nine aromatic molecules containing 10–14 carbon atoms and one or two heavy (many-electron) oxygen or chlorine atoms.

To more adequately extract the effective refractive index and other so-called metamaterial parameters from the reflection and transmission coefficients of a wave for multilayer grid nanostructures in the near-IR spectral range, the Nicholson-Ross-Weir method was modified. The rate of convergence of each extracted metamaterial parameter to a certain limit is studied with increasing number of layers of the structure. For each frequency of the light field, this limit is obviously equal to the value of the parameter that corresponds to an infinite number of layers. The effect of a separation layer of a dielectric between pairs of grids on the convergence rate of extracted parameters is studied. Bulk electrodynamic parameters of the structure are discussed.

UV spectroscopy of GK transformer oil by L. G. Gafiyatullin; O. A. Turanova; V. K. Kozlov; A. N. Turanov (97-100).
A simple and efficient method is proposed for obtaining a thin layer of transformer oil in a standard cell for the recording of UV spectra. UV and visible absorption spectra of fresh, used, and aged (under model conditions) transformer oil of the GK type have been recorded, interpreted, and compared. The method is shown to be promising for the monitoring and qualitative analysis of the composition and content of aromatic compounds in transformer oils during the operation of power transformers.

Spectral-kinetic evidence of interaction of photochromic diarylethenes with silver nanoparticles by O. I. Kobeleva; T. M. Valova; V. A. Barachevskii; M. M. Krayushkin; B. V. Lichitskii; A. A. Dudinov; O. Yu. Kuznetsova; G. E. Adamov; E. P. Grebennikov (101-105).
Spectral-kinetic investigations of the photochromism of some diarylethenes with sulfur-containing substituents in dimethylsulfoxide solutions with and without silver nanoparticles are performed. It is shown that silver nanoparticles chemically interact with diarylethene molecules, which is manifested in a change in the spectral and kinetic characteristics and photodegradation efficiency.

Control of absorption spectrum of a one-dimensional resonant photonic crystal by S. Ya. Vetrov; I. V. Timofeev; A. Yu. Avdeeva (106-111).
The crystal under consideration is a layered structure consisting of alternating layers of two materials, one of which is a resonantly absorbing gas. It is shown that the combination of the dispersion of an atomic gas with the dispersion of a photonic-bandgap structures allows one to efficiently control the transmission spectra of s- and p-polarized modes in these combined systems. It is found that the spectrum is highly sensitive to the position of the gas resonance frequency with respect to the bandgap edge and to a change in the gas pressure. The transmission, reflection, and absorption spectra of the resonant photonic crystal are studied at an angle of incidence equal to the Brewster angle of a seed photonic crystal. Possible applications of the found particular features of the dispersion of resonant photonic crystals are discussed.

Simulation of interaction of oriented J aggregates with resonance laser radiation by N. V. Vysotina; V. A. Malyshev; V. G. Maslov; L. A. Nesterov; N. N. Rosanov; S. V. Fedorov; A. N. Shatsev (112-119).
The interaction of laser radiation with single J aggregates of cyanine dyes is theoretically analyzed and numerically simulated. The quantum-mechanical calculations of the equilibrium geometry and the energies and intensities of the lowest singlet electronic transitions in pseudoisocyanine chloride and its linear (chain) oligomers are fulfilled. The data of these calculations can serve as parameters of the analyzed model of interaction of J aggregates with radiation in the one-particle density matrix approximation. This model takes into account relaxation processes, the annihilation of excitations at neighboring molecules, and inhomogeneous broadening. Assuming that the inhomogeneous broadening is absent, calculations demonstrate the existence of spatial bistability, molecular switching waves, and dissipative solitons. The effect of the inhomogeneous broadening and the radiation intensity on the effective coherence length in linear (chain) J aggregates is analyzed.

Motion of dissipative solitons in a molecular chain resonantly excited by laser radiation obliquely incident on the chain is computer simulated. The soliton motion with the velocity proportional to the small inclination angle is demonstrated.

Vortex structures of radiation for a laser whose aperture represents a multiply connected domain, i.e., a thin ring, are analytically considered. It is demonstrated that, for sufficiently large ring radii, multistability with a large number of stable vortex structures of radiation, including those with large topological charge, is achieved.

Three-component superposition states of light in a dissipative medium by S. T. Gevorkyan; M. S. Gevorkyan (126-132).
The process of the simultaneous absorption of three photons in a medium possessing weak one-photon absorption is analyzed. The mode experiencing absorption is perturbed externally via a three-photon parametric process. It is shown that a steady-state, three-component superposition state of light can exist in this system in the range where the amplitude of the state is small (small perturbations of the system). The latter condition is due to the fact that, in this range of interactions, the field spends significantly more time in one of three types of superposition states of light that form an ensemble of quantum trajectories of the system than in the other two.

Parametric doppler effect for laser pulses by N. N. Rosanov (133-135).
Transformation of a light pulse reflected from an inhomogeneity moving in a medium with a frequency dispersion is analyzed. For a quasimonochromatic light pulse (with a narrow spectrum), simple expressions are obtained for the carrier frequency and pulse length conversion factors. The results of calculations are presented for a medium with a plasma-type frequency dispersion.

The effect of filtering that arises in the scheme of 4f Fourier holography due to the boundedness of the dynamic range of holographic recording medium on the statistical characteristics of a random process, as applied to the realization of the linear predictor model, has been investigated. The numerical simulation has been performed using filter models adequate to the real characteristics of holographic recording media. Dependences relating the stationarity estimate with the process and filter characteristics are obtained.

A simple and robust eye-safe lidar was developed on the basis of a rangefinder optical scheme comprising an Er:glass laser which generates 8 mJ pulses of 1540-nm radiation with the pulse repetition rate of 0.17 Hz and a 38-mm-diameter telescope. Reliable measurements of the cloud height up to 3700 m and early forest-fire detection with a range of 3000 m were experimentally demonstrated. Theoretical estimations indicate that using an optical scheme built around a 10 Hz Er:glass lasers and 150 mm light gathering optics early forest fire detection in a range up to 6500 m can be achieved.