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Phase transition (amorphization and crystallization) of Si by ultrashort pulse laser irradiation is reported in this paper. We investigated the dependences of ablation rate and fluence for amorphization on laser pulse width.

In this paper, application of white light lidar system for the multi-wavelength depolarization measurement of clouds and aerosols will be presented. The new lidar system consisted of three depolarization channels at 450, 550 and 800 nm. The linear depolarization ratio (delta = S/P) at 450 nm can be seen to increase with increasing cloud depth due to the multiple scattering.

In this paper, application of white light lidar system for the multiwavelength backscatter measurements of clouds and aerosols will be presented. The white light continuum was generated by a focused 0.8 TW/100 fs laser pulse in a 9-m long gas cell filled with atmospheric krypton rare gas, which generated a broad spectrum of the white light. We observed the temporal evolution of the backscattered coefficient and analyzed the particle size distribution.

Summary form only given. Highly uniform implosions are important to realize the ignition in inertial confinement fusion. A substantial improvement of irradiation uniformity has been performed by replacing coherent laser beams with partially coherent light (PCL). Because the, PCL has speckle structure in the near field it causes small scale self-phase modulation resulting in spectral broadening and self-focusing in the high power operation regime. Therefore, we should, determine an operation level of the PCL to prevent optics from light-induced damage which has been observed recently in disk-type glasses at the end of amplifier chains. These filamentary bulk damages are likely to be due to the self-focusing of the PCL beam of 2 GW/cm/sup 2/ (average intensity) with a 0.6-nm bandwidth. Calculations of PCL propagation have been performed to compare with these experimental results.

Summary form only given. In the past few years, people recognized it is possible to amplify broadband optical pulses through optical parametric process with a few of well-developed nonlinear crystals. However direct amplification of the femtosecond pulses is limited by their pulse duration and associated nonlinear effects. We present both simulation and experimental studies on a stable high gain OPCPA (optical parametric chirped-pulse amplification) system which may be used as a preamplifier to replace the current complicated regenerative system and multi-pass Ti:sapphire amplifiers especially working at 1 /spl mu/m.