Propagation studies of ultrashort, intense laser pulses in plasmas

The propagation of an ultrashort, high power laser pulse focused into a xenon gas jet was measured by imaging the Thomson-scattered light emitted in the transverse direction from the gas target. An analytical expression for the free electron density of the laser-produced plasma is derived and is used to determine the laser intensity distribution at the waist of the focused laser pulse from the intensity distribution of Thomson-scattered light. With the laser intensity distribution, an expression is derived for the peak laser intensity at the beam waist in terms of the laser pulse energy and, with the known energy of the laser pulse, is used to calculate the peak value.; An expression for the differential power scattered by an electron oscillating coherently in a linearly polarized laser field is used to derive an expression for the peak laser intensity in terms of the scattered light energy. With the known response of the detector to laser radiation, this expression is used to determine the peak intensity of the laser pulse at the beam waist Both of the calculations for the peak intensity show that the peak laser intensity is about 4 {dollar}times{dollar} 10 (17) watts per square centimeter.; The propagation of an ultrashort, intense laser pulse through a laser field-ionized gas was modeled by numerically solving the nonlinear wave equation using the finite-difference method. The results of the computer model show that, for the conditions of the experiment, ionization-induced defocusing is not a limiting factor for the peak intensity of the focused laser pulse and that it does not modulate the spatial profile of the laser pulse significantly.; Spectra of the X-radiation (2.5 to 15 Angstroms) emitted from a laser-irradiated xenon gas jet in the transverse direction were obtained with a transmission grating spectrometer, a flat crystal spectrometer and a curved crystal spectrometer. Also, the propagation of the laser pulse in a xenon gas jet was imaged with a pinhole camera configured to examine X-radiation.