The ability of a pulsed laser to ran in a repetition-rate (RR) regime is an important demand to that one dedicated to operate in industry etc. For a pulsed CO2 laser the vast majority of the problems in design the appropriate systems are solved already. Among the unsolved problems one is the poor beam divergence of their radiation. The dynamical optical nonuniformities of the active medium of such lasers is the primary cause of this.

DFWM reflectivity via two-photon free carrier generation in semiconductors in middle IR range A.E.Vidavskii, V.I.Kovalev, V.M.Raukhman. Lebedev Physics Institute , Leninski av . 53 , Moscow , Russia.ABSTRACT It's shown that the effect of two-photon free carrier generation (TFCG) in semiconductors is the most promising for achieving high DFWM reflectivities R with short enough decay time ¶ in wavelength range from 1 . 5 to >9 . 5 Un . The materials which allow to achieve R up to 100% with 't of order of nanoseconds for the range of interest are presented. Some specific features of DFWM via TFCG was studied experimentally in InSb at X= 10 . 6 Lm and in Ge at ?,= 2 . 91& FUn.

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An experimental study of the generation of runaway electrons in TEXTOR has been performed. From the infrared synchrotron radiation emitted by relativistic electrons, the number of runaway electrons can be obtained as a function of time. In low density discharges fie< 1 X lOI9 m-3) runaways are created throughout the discharge and not predominantly in the startup phase. From the exponential increase in the runaway population and the ongoing runaway production after the density is increased, it is concluded that the secondary generation, i.e. the creation of runaways through close collisions of already existing runaways with thermal electrons, provides an essential contribution to the runaway production. The effective avalanche time of this secondary process is determined to be teff = 0.9 & 0.2 S .

Fig 1 Exprirnentalwurp. BS-LD.broad-stnpeiuor & '. mYetonbnm ' ' m J I o diode. Hwp. half wave plate, M prim minor, P C M phane w"j"*ate mirmr.Fig 2. Lasmg spectrum of BS-LD Salid and bmkm lines rnmn ~pcctrurn wilh a d without p hmjugete feedback, rerpedvely.Fig. 3, Focused beam panemwith in he direction pclpendiculv (x-axis) and pardlei (y-axis) UI naive layer Of BS-LD Sahd and brokeo lines mean fowxd beam panems ofoutput bsam ofBS-LD with Bod without phaw c0"jUgalC feedback rrspestive1y.17.45 CW05 Based on I d s Fast and Highly Eficient Phase Conjugate Mirror for Tbe Repetition-Rate CO2 Laser Radiation V D Bulaev', A E.Vidavskii, V.I.Kovalev, V.V Kulikov* Lebedev Physics Institute, Leninski a y , 53, 11 7924, Moscow, Russia 'State Laser Testing Center "Raduga", 600030 Radugnii, Wadimir distr , Russia Tel (095) 135 87 08, Fax: (W5) 938 22 51, c-mail. kovalev@sci lebedev ruThe ability of a pulsed laser to ran in B repetition-ate (RR) re@me is an impanam demand to that one dedicated to operate in industry etc For a pulsed CO2 l a w the vast majority of the problems in design the appropriate systems arc solved already. Among the unsolved problems one is the poor beam divergence of their radiation The dynamical optical nonuniformities of the active medium of such lasers is the prima?. cause of this.The only known method to Solve the problem radically is based on compensation ofthe nonuniformitier uith help of phase conjugation (PC). This means that PC mirror should be able to operate in RR regime too This work is done to demonstrate that based on I n k fast and highly efficient PC minor I l l is capable to work in such regime It's wellknown that heating of laser components (both optical and electrical) IS the problein wheh arise first in RR regime Correspondinsly at the first step the temperature (T) dependence of linear and nonlinear optical characteristics (absorption and nonlinear susceptibility) of InAS was investigated both theornically and experimentally Basing on the obtained data we calculated the temperature dependence of four-wave mixing reflectivity R in lnAs samples of different thtckners I It have heen found that i) in samples with I r 0 2-0.3 mm R may be kept constant ofthe ievel of-600% when T "se tiU t310K and it should drop abruptly at higher T, and it happens due to abrupt growth of the coefficient of nonlinear absorption at the border between three-and four-photon interband tmnsition in lnAs for 10 6 pm radiation. ii) in samples uith 1 3 0 1-0 OS mm the temperature-stable regime with R ic 30-S0% in the range ofT from S300K till -SOOK is possible.PC mirror have been constructed on the base of AR coated lnAs sample with I = I 7 mm located in a cavity of RR TEA CO2 laser. Independent (in Sense of the mutual coherence) lo-, pressure pumped by longitudinal discharge CO2 laser was used as the source of signal wave Both lasers w e~e capable to work with RRs up t o 12 5 Hz and total number of pulses up to I2 i) PC R is -200% in the used sample, and it remains stable (or even increase slightly) from ii) th...