Coherent population trapping in a gas of excited atoms

Coherent population trapping in a gas discharge was studied for transitions between excited levels of neon atoms. Resonances corresponding to the arising of coherent population trapping in the Λ and V schemes for Zeeman sublevels of the lower and upper working states were observed in the presence of a longitudinal magnetic field. The effect of nonlinear polarization plane rotation under coherent population trapping conditions was studied. The possibility of using the results obtained in this work for diagnostics of local magnetic fields and other plasma parameters in gas discharges was considered.     

Qubits based on spectrally selected groups of Pr<Superscript>3+</Superscript> ions in a LaF<Subscript>3</Subscript> crystal

Spectral selection, i.e., the separation of a group of particles with a spread in resonance frequencies smaller than the hyperfine splitting of working levels has been implemented by the method of burning of long-lived spectral dips in the inhomogeneously broadened absorption line of Pr³⁺ in a LaF₃ crystal. The possibility of implementing qubits (basic elements of quantum computations) on ensembles of spectrally selected particles and the main operations with them, including the manipulation of the populations of hyperfine (qubit) levels and the controlled shift of the absorption line of one spectrally selected group of ions upon excitation of another group (two-qubit operations), has been demonstrated. The decay rates of the population of hyperfine sublevels of the ground state of the spectrally selected group of particles have been measured.     

Photon echo in an atomic frequency comb in a Pr-doped LaF3 crystal

The possibility of storage of an optical pulse in a memory based on an atomic frequency comb in a Pr³⁺:LaF₃ crystal is demonstrated experimentally. A new method of storage-time control using an external electric field is proposed and experimentally implemented.     

Use of electromagnetically induced transparency for measurement of superhyperfine splitting of the levels of rare-earth metals doped in optical crystals

The results of experimental and theoretical investigations of the electromagnetically induced transparency regime on the ⁴ I _9/2-⁴ G _5/2 transition in Nd³⁺ ions doped in LaF₃ are presented. The superhyperfine splitting of the upper and lower working levels has been determined on the basis of the results obtained. A theoretical model adequately describing the parameters of the resonances of electromagnetically induced transparency has been developed by analyzing the experimental data.     

Generation of terahertz radiation by the optical breakdown induced by a bichromatic laser pulse

Experimental results are presented on generation of terahertz radiation by the air breakdown induced by a high-intensity laser pulse having not only a fundamental component, but also a second-harmonic one. A theoretical explanation of the experimental data is proposed, based on a model of field ionization of a gas by a bichromatic laser.     

Development of a compact hardware/software package for noninvasive diagnostics of skin diseases in the THz frequency range

The key elements of a mobile hardware/software package for noninvasive diagnostics of skin diseases in the THz frequency range have been designed, produced, and approved in model experiments. These elements are a compact THz oscillator based on an all-fiber femtosecond laser system and a unit for recovering electrodynamic characteristics of layered objects from scattered THz radiation spectra. Generation of 250-fs optical pulses at a wavelength of 1.03 µm with energy of 0.3 µJ and a repetition frequency of 1MHz is demonstrated and the efficiency of optical-THz conversion is found to be 5×10^?6. The proposed algorithm is constructed based on an iterative procedure and can be used for dispersive and absorbing media. It has higher operating speed in comparison with the algorithms for solving inverse problems, which are based on functional minimization methods.     

Difference-perturbation spectra of iodotyrosines and iodothyronines in polyethyleneglycols

The difference-perturbation absorption spectra of monoiodotyrosine, diiodotyrosine, triiodothyronine, and thyroxine with low- and high-molecular-mass polyethyleneglycols as perturbants have been measured and characterized. The SDP spectra, and their intensity and the position of the main maximum depend on the number of iodine atoms and the state of ionization of the hydroxyl in accordance with their electron-accepting properties. Institute of Physiology, Uzbek SSR Academy of Sciences, Tashkent. Institute of Biochemistry, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, Vol. 6, pp. 840–845, November–December, 1989.     

On the possibility of reducing the influence of laser radiation linewidth on execution of quantum logic operations using off-resonant Raman interaction

We investigate the possibility of reducing negative influence of the laser radiation linewidth on execution of quantum logical operations using off-resonant Raman interaction.