A pulsed iodine photodissociation laser with slow pumping

Abstract

A construction and exploitation of a comparatively large I photodissociation laser system (Perun) is reported. This system was constructed in cooperation between the Institute of Physics of Czechoslovak Academy of Science in Prague and the Lebedev Institute of Physics of Soviet Academy of Science in Moscow. The laser produces subnanosecond pulses of maximum 50 J and 0.5 ns in duration. Although the pumping time by Xe flashlamps is long enough for an acoustic disturbance released in the active medium to introduce an optical inhomogeneity across the whole cross section of the laser tube, the radiation can be focused in a focal spot of a power density exceeding 10 14 W/cm 2 , enough for meaningful laser target experiments both for a laser plasma production or a modification of solid surfaces. The repetition time of the shots is about 10 min. Iodine photodissociation lasersHigh-power iodine photodissociation lasers are based upon the laser transition between the two lowest fine structure levels of I atom with an energy difference 0.94 eV: /*<5 2 Pxn) -1(5 2 P 3/2 ) + M0.94 eV).(1)The wavelength 1.315 /im falls in the near infrared. The transition between the fine structure levels is of magnetic momentum type with a comparatively long radiative life time T S = 0.13 s. An interaction between the electron and nuclear angular momentum of I atom 127 I(5/2) leads to an additional hyperfine splitting of the levels to two groups of sublevels characterized by the quantum number F o f the full angular momentum (see figure 1). As shown in the scheme, the selection rules of the full angular momentum admit at low pressures of the laser mixture six radiative transitions, the strongest of which is the transition from F= 3 upper to F= 4 lower level. Collisional broadening of the hyperfine structure levels causes first an overlap at the lower level (interval of medium pressures). In this case, only two transitions remain. If the pressure is raised even further, the upper hyper-

Efficient route to saturation in collisionally pumped, soft-x-ray lasers

“…The PERUN laser of the Czech Institute of Physics in Prague supplies up to =50 J over =400 ps at 1.315 p, m with a 10-min repetition rate [31].We are presently adapting the system to provide a line focus and conservatively assume a =150 p, m, =25 mm focus will be attainable, providing an incident intensity of = 3 X 10' W cm . We discuss in detail the calculation of the hydrodynamics, atomic physics, and ray-tracing at these conditions, using a 400-ps FWHM fIattopped pulse of 100 ps rise time incident on a massive iron target.…”