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Short and ultrashort pulse lasers offer excellent advantages in laser precision machining mainly because of their high pulse energy and low ablation threshold. The complex process of laser interaction with metals limits the in-depth investigation into laser ablation. Numerical simulation is important in the study of fundamental mechanisms. This review explores the start-of-the-art methods for the theoretical simulation of the laser ablation of metals, including plasma formation and expansion. Laser-induced period surface structures are also studied.

We investigate the propagation of an intense short pulse laser of Gaussian radial profile in a tunnel ionizing gas and its subsequent role in electron acceleration to high energy. The interaction region in gas is followed by the vacuum region. The laser tunnel ionizes the gas and forms a high-density plasma on the propagation axis, which causes the laser defocusing. This laser defocusing reduces the deceleration of the electron. As a result, the interacting electron gains net energy. If the laser pulse duration is long enough, then the electron-ion recombination effect may be crucial. The divergence of the laser beam is significantly affected, and hence the net energy gain is affected for the specific parameter region. A theoretical model for laser defocusing in tunnel ionizing gas including the role of electron-ion recombination is discussed. The electron energy estimation in this regime has been studied for the gas-jet experiments.

By utilizing a pulsed laser beam of TEM(1,0)+TEM(0,1) mode, it was found numerically for the first time that an electron bunch can be effectively trapped by the transverse ponderomotive force in the transverse direction and at the same time accelerated by the longitudinal ponderomotive force to about 378 MeV at the laser peak intensity of I∼5.48×1018 W/cm2. In addition, the electron bunch size is preferably small: at this laser intensity the electron bunch thickness is ∼10λ in the longitudinal direction and the bunch radius is about 625λ in the transverse direction.

Time resolved x-ray images with 7 ps resolution are recorded on relativistic short-pulse laser-plasma experiments using the dilation x-ray imager, a high-speed x-ray framing camera, sensitive to x-rays in the range of ≈1−17 keV. This capability enables a series of 2D x-ray images to be recorded at picosecond scales, which allows for the investigation of fast electron transport within the target with unprecedented temporal resolution. An increase in the Kα-emission spot size over time was found for targets thinner than the recirculation limit and is absent for thicker targets. Together with the observed polarization dependence of the spot size increase, this indicates that electron recirculation is relevant for the x-ray production in thin targets.

One-and-one-half-dimensional particle-in-cell (PIC) modeling with restored short-encounter collisional behavior is used to model the interaction of high-intensity short laser pulses with plasmas. The role of Coulomb collisions in expanding thin plasma targets at solid density is particularly investigated. It is shown that collisions play an important role for plasma expansion and ion acceleration mechanisms, even at high laser intensities.

Thomson scattering is well used as a diagnostic in many areas of high energy density physics. In this paper, we quantitatively demonstrate the practicality of using Thomson scattering as a diagnostic of short-pulse laser-plasma experiments in the regime, where the plasmas probed are at solid density and have temperatures of many hundreds of eV using a backlighter produced with an optical laser. This method allows a diagnosis both spatially and temporally of the density and temperature distributions in high energy density laser-plasma interactions which is independent from, and would act as a useful complement to, the existing spectroscopic methods.

Proton generation from the interaction of an intense, short pulse laser with a foil target is simulated using the particle-in-cell hybrid code LSP. The efficiencies for proton production are compared for foils having thin coatings of CH, CH2, CH4, and LiH, as well as heavy hydrides such as ErH3. Enhanced efficiencies are found for both light hydrogen-rich compounds and for heavy hydrides, which in the latter case approach the pure H result. A simple model reproduces these results over a wide range of materials.

Since moving to a new location in March of 1999, Bechtel Nevada–Livermore Operations has established a modern laboratory for the characterization of optical and x-ray diagnostics for high temperature plasmas. Some of the facilities include a short pulse laser facility, a streak tube production facility, a microchannel plate characterization laboratory, an optical streak camera calibration laboratory, and a charge coupled device calibration laboratory. Descriptions of the facilities will be presented as well as examples of data taken at the laboratory. Future upgrades to the facility will be discussed.

Using a repetitively pulsed nitrogen laser of 100‐kW peak power and 10‐nsec duration, the Raman scattering cross sections at 3371 A for various gas species relative to that of molecular nitrogen have been measured by a gated photon counting technique. The gases studied include N2, O2, CO, CO2, NO, SO2, C3H6, and C3H8. A statistical correction formula has been derived and applied to the apparent count rate to avoid possible errors due to the finite recovery time of the counter and its inability to distinguish between single‐ and multiple‐photon arrival events within the very short time gate. The resultant accuracy of the present measurements is accordingly estimated to be better than ± 5%.