| A powerful subpicosecond laser system, based on solid state (Ti:Al 2O3) front end and gas excimer (KrF*) amplifiers, has been developed. It is capable of producing 40–50 mJ pulses at 248 nm (285 fs pulse duration) with 2 Hz repetition rate. That radiation can be focused to intensities greater than 1017 W/cm2 and cause the optical field ionization of lithium. The system was used in experiments on gain generation in hydrogen-like Li III. Lasing action in hydrogen-like Li III 2-1 transition to ground state (13.5 nm) has been demonstrated for the first time. Gain G = 11 cm−1 in 5-mm long plasma column, created in LiF microcapillary, was measured. The observed gain-length product was GL = 5.5. In another set of experiments an inversion population between levels n = 3 and n = 2 in hydrogen-like BV was created using a low-energy compact laser system at 1 Hz repetition rate. Gain G = 17 cm−1 at 26.2 nm was measured in 3 mm long B2O3 microcapillary, which corresponds to GL = 5.1. The entire experimental setup can be fit on a single medium size optical table. Also propagation of laser radiation through plasma, created in microcapillaries has been investigated at various experimental conditions. Real-time plasma probing with low intensity HeNe laser beam has been performed. |
