We describe the optical, radiative, and laser-plasma physics of a new type of nanostructured surface especially promising as a very high absorption target for high-peak-power subpicosecond laser-matter interaction. This oriented-nanowire material, irradiated by 1 ps pulses at intensities up to 10(17) W cm(-2), produces picosecond soft x-ray pulses 50x more efficiently than do solid targets. We compare this to "smoke" or metallic clusters, and solid nanogroove-grating surfaces; the "metal-velvet" targets combine the high yield of smoke targets with the brief emission of grating surfaces.

We have developed a fiberless 1-TW all-Nd:glass chirped-pulse-amplification laser system that uses high-contrast 0.8-1.4-ps pulses produced directly from a Nd:glass feedback-controlled oscillator. Employing grating-only expansion and compression, the system produces clean (~10(7) contrast ratio) 1-J, 1- 1.4-ps recompressed pulses without added pulse cleaning. Clean microjoule-energy pulses from the oscillator require less subsequent amplification than cw oscillator schemes, thereby minimizing gain-bandwidth narrowing and offering improved contrast with amplified stimulated emission background.

Articles you may be interested inRadial profile measurement of electron temperature in edge stochastic magnetic field layer of LHD using intensity ratio of extreme ultraviolet line emissionsa) Rev. Sci. Instrum. 83, 10E509 (2012);

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We have developed a self-healing mercury-wetted target as a practical source of soft x-ray radiation for photoexciting extreme ultraviolet lasers. A threaded rod, rotating in a pool of mercury, demonstrates a soft x-ray conversion efficiency similar to that of expendable gold-coated targets in synchronous photopumping of a photoionization Xe2+ laser at 109 nm. Surfaces self-heal or are continuously regenerated by rewetting, while mercury debris is removed by evaporation from the target chamber walls and optics. Long target lifetime and self-cleaning performance of the new target system are attractive features in future high-repetition-rate, high-throughput applications for photopumping of extreme ultraviolet or soft x-ray lasers, and more generally as incoherent sources for soft x-ray lithography and spectroscopy.

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The FCM–CPA laser system at the University of Toronto uses a feedback-controlled Nd: glass oscillator to directly generate high-contrast 1-ps pulses at 1.054µm—ideal for an all-glass, no-fibre chirped-pulse amplification and compression laser system. Recompressed pulse contrast is nearly 108, final energy is >1J in a 1-ps pulse, in a relatively simple-to-operate system. With this system, and theoretically, we have been studying the use of isoelectronic line ratios in determination of temperature and electron energy distributions in picosecond laser-plasmas. We find that this class of spectroscopic line ratios is especially well-suited to highly transient plasmas, because the similarity of the lines leads to a diagnostic which is quasi-steady-state—more nearly ‘local’ in its time response. Also described are investigations in soft x-ray photopumped XUV laser systems, using the emission from travelling-wave laser-plasmas formed on self-healing mercury-wetted targets; these targets are particularly useful for high-repetition-rate applications.