Dynamics and spectrum of giant pulsed lasing in a composite resonator with an electrooptic Q-switch

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 4, pp. 540–546, October, 1990.     

Analysis of lasing threshold of a nuclear-pumped gas laser depending on the lasing medium residence time in the laser module case

It is shown experimentally that an increase in the lasing mixture residence time in the case of a laser module over 60–120 min prior to an experiment elevates the lasing threshold and deteriorates the energy parameter of the laser. The worsening of the energy parameters of the laser may be due to accumulation of impurity gases. It is shown that the presence of impurities affects the working characteristics of the laser media under investigation to various extents.     

Dynamics of a lasing atom in hot plasma

We study theoretically the dynamics of lasing atoms in a very hot plasma capillary, which produce coherent X-ray radiation. The atoms which participate in the lasing action are treated as a dilute gas, embedded in the plasma, whose electrons play the dominant role in inducing relaxations and decoherences. The active atom interacting with the electron reservoir in thermal equilibrium is described by a general Hamiltonian. In analogy with a radiation reservoir, by eliminating the degrees of freedom of the electron reservoir, the evolution rates of the Master Equation, i.e. the transition rates for the populations and dephasing rates for coherences, are calculated. It is demonstrated, by going beyond the dipole approximation, that the contribution of the adiabatic dephasing rate is significant compared to that of the non-adiabatic rate, in contrast to the case of a radiation reservoir. We also study other dephasing mechanisms, e.g. the motion of the lasing atoms center of mass, and the role of other atomic levels.Received: 13 May 2004, Published online: 24 August 2004PACS: 52.20.Hv Atomic, molecular, ion, and heavy-particle collisions - 32.70.Jz Line shapes, widths, and shifts     

Acousto-optical effect in the luminescence excitation spectrum of HgI2

A study of the photoluminescence excitation spectrum in a crystal of mercury diiodide is reported. Each of the two luminescence bands peaking at 543 and 572–575 nm investigated was found to have its own excitation spectrum. The excitation spectrum of the 575-nm line in the long-wavelength doublet band has been observed to be sensitive to strong ultrasound vibrations and preliminary irradiation of the sample by 590-nm light. This line is associated with radiative recombination of photocarriers at intrinsic point defects (vacancies or iodine and mercury interstitials) located close to dislocations. The binding energy of the photosensitive center to a dislocation was estimated from the change in the excitation spectrum. Fiz. Tverd. Tela (St. Petersburg) 41, 1965–1968 (November 1999)     

Dynamics of activated escape and its observation in a semiconductor laser

We report a direct experimental observation and provide a theory of the distribution of trajectories along which a fluctuating system moves over a potential barrier in escape from a metastable state. The experimental results are obtained for a semiconductor laser with optical feedback. The distribution of paths displays a distinct peak, which shows how the escaping system is most likely to move. We argue that the specific features of this distribution may give an insight into the nature of dropout events in lasers.     

Mid-gap luminescence and its excitation spectrum in trigonal selenium single crystals

Trigonal selenium shows in addition to the narrow “band-edge” luminescence due to the decay of free excitons a broad photoluminescence band in the i.r. region very similar to the luminescence in amorphous selenium. This mid-gap luminescence arises at low temperature from the excitation of a defect and at higher temperature from the trapping of free excitons, both processes involving considerable relaxation of the defect. The excitation spectra exclude photoluminescence via the excitation of free carriers.     

Simultaneous dual-wavelength lasing of an erbium-doped fibre laser over wide spectrum range by intracavity loss optimisation

This letter reports a new technique to achieve a wide range of simultaneous dual output lasing of an erbium-doped fibre laser. The range covers a wide spectrum of 30 nm. This range is achieved by optimising the intracavity loss of the fibre loop in the laser. The wavelength is tuned via a tuneable bandpass filter. These dual lasing outputs are kept within a 0.5 dB power difference.     

Dynamic nonlinear effect on lasing in a random medium

We have studied both experimentally and numerically the dynamic effect of nonlinearity on lasing in disordered medium. The third-order nonlinearity not only changes the frequency and size of lasing modes, but also modifies the laser emission intensity and laser pulse width. When the nonlinear response time is longer than the lifetime of the lasing mode, the nonlinearity changes the laser output through modifying the size of the lasing mode. When the nonlinear response is faster than the buildup of the lasing mode, positive nonlinearity always extracts more laser emission from the random medium due to the enhancement of single particle scattering.