Spatial coherence of x-ray laser emission from neonlike germanium after prepulse

The time-integrated spatial coherence of neonlike germanium x-ray laser radiation has been studied with a new dispersing coherence diagnostic. Angle-dependent spatial coherence data are recorded by sampling the diverging beam at each lasing wavelength in several directions simultaneously. Measurements of the spatial coherence, and hence effective source sizes, relevant to the output beams from double-slab targets for the J = 2-1 spectral lines at wavelengths 28.6, 23.6, and 23.2 nm and for the J = 0-1 line at 19.6 nm show differences, which indicate different conditions in the plasma volume amplifying these emissions. Targets are pumped by subnanosecond pulse drivers, with and without a prepulse, but 19.6 nm emission is detected only in the prepulsed case. The differences are discussed in terms of the time evolution of the spectral lines. (C) 1997 Optical Society of America.

The influence of prepulse level on the 3p-3s XUV laser output from Ne-like ions of Zn, Cu and Ni

We have studied the effect of prepulses in enhancing the efficiency of generating ASE beams in soft X-ray laser plasma amplifiers based on pumping Ne-like ions, Slab targets were irradiated with a weak prepulse followed by a main plasma heating pulse of nanosecond duration, Time-integrated; time and spectrally resolved and time and angularly resolved lasing emissions on the 3p-3s (J=0-1) XUV lasing lines of Ne-like Ni, Cu and Zn at wavelengths 232 Angstrom 221 Angstrom and 212 Angstrom respectively have been monitored. Measurements were made for pre-pulse/main-pulse intensity ratios from 10(-5)-10(-1) and for pump delay times of 2 ns and 4.5 ns. Zinc is shown to exhibit a peak in output intensity at similar to 2x10(-3) pre-pulse fraction for a 4.5 ns pump delay, with a main pulse pump intensity of similar to 1.3x10(13) W cm(-2) on a 20 mm target. The Zn lasing emission had a duration of similar to 240 ps and this was insensitive to prepulse fraction. The J=0-1 XUV laser output for nickel and copper increased monotonically with prepulse fraction, with copper targets showing least sensitivity to either prepulse level or prepulse to main pulse delay. Under the conditions of the study, the pre-pulse level was observed to haveno significant influence on the output intensity of the 3p-3s (J=2-1) lines of any of the elements investigated.

A time-resolved spectroscopy study of the resonance-line emission in the Ge XXIII XUV laser

A comparison is presented of the temporally resolved resonance-line emission from the Ne-like Ge XUV laser (pumped with nanosecond pulses) with the predictions for the same emission from the hydro-atomic code EHYBRID. The specific lines chosen were the two 3s-2p Ne-like lines at 10.01 and 9.762 Angstrom, and the 3s-2p F-like group of lines in the 9.4-9.6 Angstrom region. Modification of the code to include 112 excited levels of the F-like ion facilitated a direct comparison between experiment and model of (i) the temporal variation of the emissions and (ii) the variation of the peak intensity ratios of the F-like to Ne-like emissions with irradiance on target.

EMISSION STUDIES OF THE PLUME PRODUCED DURING YBA2CU3O7 FILM PRODUCTION BY LASER-ABLATION

The optical plume emissions produced on excimer laser ablation of a YBa2Cu3O7 target are reported and identified with the various atomic, ionic, and molecular species present. The spatial and temporal distribution of these emissions were studied as a function of the laser fluence and oxygen pressure. At the laser fluences used (4-6 J/cm(2)) some target material is ablated or evaporated directly in molecular form. In addition efficient formation of molecular oxides is observed at the contact front of the expanding plume with the surrounding oxygen atmosphere. The intensity and spatial distribution of oxide emission in the visible plume therefore provides a sensitive diagnostic for optimization of substrate location and deposition conditions.

Transverse Spreading of Electrons in High-Intensity Laser Fields

We show that for collisions of electrons with a high-intensity laser, discrete photon emissions introduce a transverse beam spread that is distinct from that due to classical (or beam shape) effects. Via numerical simulations, we show that this quantum induced transverse momentum gain of the electron is manifest in collisions with a realistic laser pulse of intensity within reach of current technology, and we propose it as a measurable signature of strong-field quantum electrodynamics.

Temporal structure of attosecond pulses from laser-driven coherent synchrotron emission

The microscopic dynamics of laser-driven coherent synchrotron emission transmitted through thin foils are investigated using particle-in-cell simulations. For normal incidence interactions, we identify the formation of two distinct electron nanobunches from which emission takes place each half-cycle of the driving laser pulse. These emissions are separated temporally by 130 attoseconds and are dominant in different frequency ranges, which is a direct consequence of the distinct characteristics of each electron nanobunch. This may be exploited through spectral filtering to isolate these emissions, generating electromagnetic pulses of duration ~70 as.