The time-dependent characteristics of the second-harmonic generation o
f a short pulse are investigated theoretically. Transient coupled-wave
equations are necessary to describe the time-dependent process of the
second-harmonic generation of a short pulse. It is found that the fun
damental waves experience both pulse broadening and compression with d
ifferent waveform distortion during the frequency-doubling process. Th
e pulse width of a frequency-doubled wave broadens monotonically along
the crystal length. There is no phase distortion in the case of exact
phase matching. Phase modulation (i.e., chirp) occurs only when there
is phase mismatch and chirp can be determined by the phase mismatch.
(C) 1997 Optical Society of America.