Nonlinear conversion of the frequency of picosecond pulses

Results are presented of calculations of the spectral profile and width, and of the energy of sumfrequency radiation excited in a nonlinear crystal by mixing of a small ultrashort signal pulse and a long high-intensity pump pulse. The various sum-frequency generation conditions are classified according to the character of the nonlinear and dispersion effects. Particular attention is paid to nonlinear generation. Calculations are made by analytic and numerical techniques.