The study of light induced structures in liquids and solids

Abstract

A number of interaction mechanisms of laser light with matter are reviewed; these include laser induced damage, nonlinear optics and various types of scattering. A comprehensive experimental study of laser induced damage is described. This damage is caused to a glass surface bearing a thin gold film while being illuminated by an argon ion laser beam. Small diffraction gratings can be produced by placing thin metallic films inside a ruby laser cavity. In such an arrangement the intense light of the laser is obliquely incident on the thin partially absorbing film simultaneously from two opposite directions, heating occurs, therefore, much more rapidly at the antinodes than at the nodes of the resulting standing wave. This heating can cause evaporation and ionization of the film. Since the film intersects the antinodes of the standing wave in a series of lines, this removal of the film material results in the creation of a diffraction grating. A time resolved investigation has been made of the development of such gratings in a number of metallic films, and the effect of film thickness, incident laser intensity, and angular orientation of the film has been studied. A solution of the time dependent stimulated scattering equations is obtained. Using a new approach it is shown that by suitable convolutions, the time dependent stimulated scattering gain profile for absorbing and nonabsorbing liquids can be directly obtained from the steady state scattering results. Laser mode locking techniques are detailed and a description is given of a ruby ring laser system. This system was able to deliver pulses as short as 25 picoseconds in duration and with peak intensities of 100 MW/cm2.