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We have performed an experimental investigation of Ti-, [B.sub.4]C-, B-, and Y-based multilayer mirrors for the soft x-ray-extreme ultraviolet (XUV) wavelength region between 2.0 and 12.0 nm. Eleven different material pairs were studied: Ti/Ni, Ti/Co, Ti/Cu, Ti/W, [B.sub.4]C/Pd, B/Mo, Y/Pd, Y/Ag, Y/Mo, Y/Nb, and Y/C. The multilayers were sputter deposited and were characterized with a number of techniques, including low-angle x-ray diffraction and normal incidence XUV reflectometry. Among the Ti-based multilayers the best results were obtained with Ti/W, with peak reflectances up to 5.2% at 2.79 nm at 61 [degrees] from normal incidence. The [B.sub.4]C/Pd and B/Mo multilayer mirrors had near-normal incidence (5 [degrees]) peak reflectances of 11.5% at 8.46 nm and 9.4% at 6.67 nm, respectively, whereas a Y/Mo multilayer mirror had a maximum peak reflectance of 25.6% at 11.30 nm at the same angle. The factors limiting the peak reflectance of these different multilayer mirrors are discussed. Key words: Soft x ray, extreme ultraviolet, XUV optics, multilayer mirrors, normal incidence reflectance, thin films, interfaces, sputtering, enthalpy, Gibbs free energy of formation, titanium, nickel, cobalt, copper, tungsten, boron, boron-carbide, palladium, molybdenum, yttrium, silver, niobium, carbon.

We describe a technique for spectrally and temporally resolving the kilo-electron-volt emission from ultrashort plasmas produced from solid targets with a tabletop terawatt 400-fs laser. The first time-resolved Al spectra (near 8 Angstroms) obtained with a 2-ps time resolution are presented. The results clearly demonstrate that the resonance emission width decreases as the plasma density increases. The ultrafast K(sub Alpha) emission component is also measured in our experimental conditions.

A convenient method is described for optical characterization of thin films during growth. The method has been demonstrated on lead zirconate titanate (PZT) films deposited by pulsed laser ablation for various temperatures. The optical constants of the PZT films as well as the film growth rate were determined in situ by fitting (with three free parameters) the calculated reflectance as a function of film thickness to the experimental reflectance curve as a function of deposition time, as obtained by unpolarized laser reflectometry. The fitted parameters are the uniform complex PZT refractive index and the layer thickness (assumed proportional to time), with the complex refractive index of the platinum substrate being measured previously. These results compare well with the subsequent ellipsometric measurements made to assess the precision of the reflectomerry technique. Key words: Laser reflectometry, refractive index, in situ material characterization.

The ablated depth and volume per laser pulse from an aluminum target were measured for pulse durations that ranged from 80 fs to 270 ps at an average fluence of approximately 100 J/cm2 and a wavelength of 0.8 microm. The ablated volume showed a flat maximum for subpicosecond pulses and a minimum for approximately 6 ps. The crater diameters were rather constant up to pulse durations of approximately 6 ps and increased for larger pulse durations. As a result, the ablated depth also showed a plateau for subpicosecond pulses but decreased monotonically with pulse duration. A physical interpretation of these results and their consequences for laser applications are discussed.