Abstract

A Ti:sapphire based laser system provided 30-fs pulses centered at 800 nm with up to 3 mJ energy was used in the experiment. The input beam was focused by a concave mirror with radius of 3 m into a 1.5 m long glass cell. No iris-diaphragm or other beam reshaping tools were used for filament adjustment. The gas cell was filled with SF₆ or for comparison with Ar at variable pressure of 0.1-0.7 bar. After the filament start point the laser radiation was spatially confined and propagated through the entire gas cell. Diameter of central, bright part of the beam was in a range of 2 mm directly after the output window. The output spectra recorded directly after the cell filled gases are shown in Fig. 1. The filament in SF₆ demonstrate qualitatively different spectral shape, as compared to Ar, with dramatic enhancement in frequency conversion out of fundamental spectral range especially towards the higher-frequency domain. FWHM of the detected spectrum reached almost octave bandwidth of 440-875 nm.

© 2011 Optical Society of America