Professor Simon Hooker

Abstract:

An optically pumped laser that operates in the VUV region of the spectrum with pulse energies in the millijoule range is proposed. The laser is expected to oscillate on ten to 13 new laser lines between 158 and 250 n. The transmission of the F2 pump laser output was measured as a function of NO pressure to deduce the absorption cross section. The absorption was also modeled using spectral rate equations. The model reproduces the observed transmission very well and predicts that the broadening of the absorption line is due to rapid quenching of the upper level. The measurements are not consistent with the results reported by T.J. McKee The predicted upper level population is of the order of 8 × 1014 cm-3 for an NO pressure of 800 mbar, which would give a small signal gain of ≈ 1 cm-1 for the strongest line. On the basis of this it appears to be possible to realize the proposed laser.

Abstract:

Hydrodynamic optically-field-ionized (HOFI) plasma channels up to 100mm long are investigated. Optical guiding is demonstrated of laser pulses with a peak input intensity of $6\times10^{17}$ W cm$^{-2}$ through 100mm long plasma channels with on-axis densities measured interferometrically to be as low as $n_{e0} = (1.0\pm0.3)\times10^{17}$cm$^{-3}$. Guiding is also observed at lower axial densities, which are inferred from magneto-hydrodynamic simulations to be approximately $7\times10^{16}$cm$^{-3}$. Measurements of the power attenuation lengths of the channels are shown to be in good agreement with those calculated from the measured transverse electron density profiles. To our knowledge, the plasma channels investigated in this work are the longest, and have the lowest on-axis density, of any free-standing waveguide demonstrated to guide laser pulses with intensities above $>10^{17}$ W cm$^{-2}$.