[en] We present a study of the characteristics of quantum-cascade lasers with a wavelength around 8 μm in a wide temperature range up to 338 K (+65⁰C). Spectral studies reveal lasing in two bands around ∼ 7800 nm and ∼ 8100 nm. The observed competition between short and long wavelength lasing lines leads to non-monotonic behaviour of the radiation intensity in relation to the pumping current. (paper)

[en] We studied the generation of valley dependent current by adiabatic quantum pumping in monolayer graphene in the presence of electric potential barriers, ferromagnetic field and strain. The pumped currents in the two valleys have same magnitudes and opposite directions; thus, a pure valley current is generated. The oscillation of the pumped pure valley current is determined by the Fabry-Perot resonances formed in the structure. In our calculation, the pumped pure valley current can be as high as 50 nA, which is measurable using present technologies. The proposed device is useful for the development of graphene valleytronic devices

[en] Long pulse (200 ns) XeCl excimer laser emission (lambda = 3,080 A), has been obtained when Ne/Xe/HCl mixtures are excited by an electron beam and X ray assisted discharge either at room temperature or at very low temperature. Absorbed discharge energy is several orders of magnitude higher than the absorbed beam energy. Maximum specific laser energy is 3 J/l at room temperature for a 16 cm gain length and an absorbed discharge energy of 150 J/l

[en] The problem of interaction of radiation having arbitrary polarization and intensity with 1/2-1/2 and 1-0 resonant systems was solved. Exact expressions for the vectors of orientation of lower and upper states of the 1/2-1/2 system and for the vector of orientation and tensor of alignment of the 1-0 system in the field of elliptically polarized radiation are obtained. The influence of disorientating atomic collisions on the process of optical pumping was also studied. 10 refs

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[en] Published in summary form only

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[en] The absorption analysis is introduced with an experimental set-up of the CO₂ pump laser and the CF₄ laser. Special attention is paid to the frequency stabilization scheme of CO₂ laser and the description system. Attention is also focused on the continuous wave output of the CF₄ laser. The directional dependence of the gain, and thus of the emitted power is described. It was found that more radiation is emitted in the direction co-propagating than counter-propagating with the pump laser, known as 'gain anisotropy'. This work performs a quantitative study of pump threshold 'gain anisotropy' confirming theoretical predictions, by a study of pump threshold powers. An experimental study of the output of the continuous wave CF₄ laser as a function of pressure and temperature is given. The frequency of the pump laser was stabilized using an opto-acoustic cell. Experiments with a resonance enhanced low pressure opto-acoustic cell is introduced. The experimental results were compared with the predictions of a model, which incorporates a description of the cell geometry and the properties of the active gas in the cell. Corrections were made to describe the low pressure behaviour of the cell. (A.S.). 113 refs.; 42 figs.; 12 tabs

[en] The internal structure of a particle an atom or other quantum system in which the excitation energies are discrete undergoes change when exposed to pulses of near-resonant laser light. This tutorial review presents basic concepts of quantum states, of laser radiation and of the Hilbert-space state vector that provides the theoretical portrait of probability amplitudes the tools for quantifying quantum properties not only of individual atoms and molecules but also of artificial atoms and other quantum systems. It discusses the equations of motion that describe the laser-induced changes (coherent excitation), and gives examples of laser=pulse effects, with particular emphasis on two-state and three-state adiabatic time evolution within the rotating-wave approximation. It provides pictorial descriptions of excitation based on the Bloch equations that allow visualization of two-state excitation as motion of a three-dimensional vector (the Bloch vector). Other visualization techniques allow portrayal of more elaborate systems, particularly the Hilbert-space motion of adiabatic states subject to various pulse sequences. Various more general multilevel systems receive treatment that includes degeneracies, chains and loop linkages. The concluding sections discuss techniques for creating arbitrary pre-assigned quantum states, for manipulating them into alternative coherent superpositions and for analyzing an unknown superposition. Appendices review some basic mathematical concepts and provide further details of the theoretical formalism, including photons, pulse propagation, statistical averages, analytic solutions to the equations of motion, exact solutions of periodic Hamiltonians, and population-trapping 'dark' states. (author)