Abstract

There are many unique advantages to using picosecond infrared pulses for nonlinear experiments. For example: (i) The photon energy is much less than the bandgap energy of many important semiconductors. Thus different nonlinear processes are likely to be important with high power density picosecond pulses. Furthermore, these processes can be studied in a frequency range where, at least at low powers, these materials are highly transparent. (ii) The laser wavelength, through the parameter Ḛλ (Ḛ is the electric field of the light) is important for determining the interaction of light with materials, particularly with free carriers in solids or plasmas. At constant intensity, much higher values of this parameter can be reached with infrared radiation. (iii) Infrared photons are resonant with molecular vibrational transitions. Multiphoton vibrational excitation and relaxation studies may well be conveniently carried out in this wavelength region.

© 1984 Optical Society of America