Excitation of UV radiation by a pulsed-periodic discharge in xenon

Optoelectrical characteristics of a pulsed-periodic discharge in xenon are investigated experimentally under conditions such that the product of the electrode gap length and the gas pressure is in the range of 4–20 Torr cm. High conversion efficiency of the energy deposited into vacuum UV radiation in a discharge sustained by 0.1-gms voltage pulses at a repetition rate of 1–10 kHz is demonstrated. It is shown that this effect is related to the fast expansion of the negative glow occurring after each discharge ignition. The conditions are determined under which the discharge is not accompanied by the heating and sputtering of the cathode.     

Nonlinear processes in the optical medium of a high-power neodymium laser

The article is devoted to an analysis of the nonlinear processes that arise when powerful beams propagate in the optical medium of an Nd laser and influence its output parameters. A review is presented of the methods of theoretically describing the processes of temporal and spatial self-focusing, and experimental data are cited that illustrate the character of the course of the self-focusing in the generators and amplifiers of a high-power laser. Possible methods of suppressing self-focusing in a laser installation are considered.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 103, pp. 84–117, 1978.     

Stimulated Raman scattering of copper vapour laser radiation in optical fibres

Wideband frequency conversion of copper vapour laser radiation has been achieved by stimulated Raman scattering in multimode silica fibres. Up to nine Stokes' orders have been generated in the 511 to 649 nm spectral region with a conversion efficiency greater than 90% of the fibre output. Four-wave mixing processes involving laser and Stokes' lines have also been observed.     

Transverse spectra of radiation processes in a medium

A formalism is developed for evaluation of the transverse momentum dependence of the cross sections of radiation processes in a medium. The analysis is based on the light-cone path integral approach to the induced radiation. The results are applicable in both QED and QCD. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 3, 181–186 (10 August 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Forward-scattered optical radiation in a bipolar ionized medium

We study the dependence of the forward-scattered radiation from a point source in wood smoke on the electrical conductivity of the medium. It is shown that as the number of airborne ions in the medium increases, the intensity of the forward-scattered radiation increases because of ionization. Intensity variations are due to the growth of particles because of coagulation, which occurs because the airborne ions are cooled on the surfaces of the scattering centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 82–87, February, 1986.     

Ablation of an optically homogeneous absorbing medium by scattered pulsed laser radiation

We have studied the ablation of an aqueous CuCl₂ solution in a pulsed Nd:YAG laser field featuring a speckle-patterned structure characterized by spatial radiation energy fluence fluctuations. This leads to a nonuniform distribution of the energy absorbed in the bulk of the sample being irradiated and causes local overheating centers to form, wherein ablation is observed to take place at laser energy fluences below the threshold value found in experiments with a homogeneous laser beam. This effect should be manifest in the laser irradiation of biotissues which, as a rule, scatter light strongly.     

Ultrafast optical switching of an ionized medium by interfering ultrashort laser pulses

Multibeam ionization of gas and condensed-phase media with interfering ultrashort laser pulses can help to substantially increase the maximum field intensity and the density of free electrons attainable in the focus of the laser field relative to the regime of single-beam ionization. Multibeam ionization schemes offer new solutions for laser micro- and nanomachining, micro- and nanosurgery, spectral and temporal transformation of ultrashort light pulses, as well as remote sensing of the atmosphere. Subfemtosecond changes in the local refractive index induced in the regime of multibeam tunneling ionization enable the high-speed switching of optical signals.     

Transformation of optical radiation by fast-moving smooth inhomogeneities of a medium

For the problem of the reflection and transmission of monochromatic radiation by a moving smooth inhomogeneity of parameters of a motionless transparent medium, transport equations are derived and an approximate solution to these equations is obtained for the case of weak reflection. Estimates of the effects for quartz in the transparency region are given.     

Terahertz radiation from a nonlinear slab traversed by an optical pulse

We report on the theoretical calculations considering collinear electromagnetic radiation at the propagation of an optical pulse through a slab of nonlinear material. Calculated waveforms of the radiated field fit well to the experimental dependencies showing the remarkable similarities between the radiation at nonlinear wave interaction and the radiation phenomena of moving external charges, similarly to discussed in the Tamm Problem and transition radiation of moving external charges.     

Initiation of heterogeneous photocondensation processes by laser radiation

A physical model of heterogeneous photocondensation processes initiated in a saturated-vapor atmosphere by intense laser radiation is proposed. Several mechanisms of induction of nonlinear supersaturation in the medium are examined. The concentration and maximum radius of the formed drops for a prescribed nonlinear supersaturation are calculated. It is shown that the laser-flash energy introduced initially into the medium and ensuring the transfer of the condensation nuclei across the forbidden radius gap is capable of initiating a much more energetic macroprocess of drop generation from supersaturated vapor.Part of this work was reported at the Regional Applied Science Conference, Tomsk, Oct. 27–30, 1977. Proceedings of Physicotechnical Section. Tomsk State Univ., p. 81.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 80–84, June, 1979.     

热容模式下激光介质的动态光学畸变

 开展了热容模式下激光介质动态光学畸变研究,初步分析了温度梯度、光弹效应及介质端面变形对整个波前畸变带来的影响,并将光学畸变转化为谐振腔损耗,数值模拟了热容激光器输出功率随时间的变化规律,模拟结果表明：当激光器工作温度低于400 K时,由粒子数玻耳兹曼分布引起的功率下降可以忽略,动态热效应是实验中热容激光器输出功率随时间快速下降的原因。     

Plasma-chemical processes in the active medium of a CO laser

The concentrations of plasma-chemical products (C, O, CO₂, C₂, and C₃O₂) were measured under conditions typical of the active medium of an electrical discharge CO laser. The dependence of the concentration of C₃O₂ molecules on the experimental conditions was studied. A reaction scheme responsible for the concentration of C₃O₂ molecules formed in the discharge was proposed.