Picosecond spectroscopy and research on fast processes

The development of techniques for generating picosecond pulses and for isolating and amplifying individual pulses, together with the use of the Kerr effect initiated by the electric field of an intense light wave (the ultrafast optical/shutter), has made it possible to develop various direct optical methods for measuring short times and investigating the kinetics of fast processes in the picosecond range. Methods for the direct measurement of molecular anisotropy relaxation times in various liquids and the lifetimes of optical and acoustic phonons in liquids and solids are described, and results obtained by these methods are given and compared with the values obtained by indirect methods. The results of direct measurements of the luminescence decay times of certain dyes are presented, as well as the results of studies of the kinetics of the absorption of light in dense electron-hole plasmas in semiconductors and of the solvation of electrons in solutions. The use of the ultrafast optical shutter to investigate the structures of picosecond pulses, to obtain separate photographs of objects lying close together, to look through fog, and to obtain successive photographs at picosecond exposures is described. A method of amplifying weak picosecond pulses and recording them on videotape for subsequent display on a kinescope is also described.