Spectra of Giant Pulses from a Ruby Laser

Abstract

THE spectral character of the giant pulse¹ emitted by a ruby laser has been investigated to determine the suitability of this source for plasma light scattering experiments. A ‘Trion LS-4: laser’ system consisting of a 10 cm × 1.3 cm × 1.3 cm total internal reflexion ruby with 90° c-axis orientation, pumped by means of a 10,000 joule spiral xenon flash-lamp, has been modified to produce giant pulses by the addition of a Kerr cell, a Nicol prism, and a 48 per cent reflectivity dielectric mirror acting as external reflector. Giant pulses which last for less than 40 n sec were produced by switching the Kerr cell with a low inductance thyratron circuit. The Kerr cell was normally gated open for 1 µsec. Throughout the experiment the pumping energy delivered to the flash-lamp was maintained at 6,700±300 joules, which is about 25 per cent above threshold for normal relaxation oscillations in this crystal at the temperature at which it was operated, namely 126±3° K. High-resolution spectroscopy of these pulses was carried out with a variable gap silvered Fabry–Perot interferometer which had a resolving limit of 0.011 cm⁻¹ for 1 cm separation of the mirrors. To ensure that only giant pulse light was recorded, a Barr and Stroud framing camera operated at a speed of 10 µsec per frame was used to photograph the interference fringes on Gaevert infra-red sensitive film (‘Scientia 52A86’).