We demonstrate a nondestructive probing technique to investigate the inner
crystal domain structure of ferroelectric crystals by analyzing the teraher
tz wave forms generated by optical rectification. Quantitative analysis of
the domain structure has been performed for the domain width in periodicall
y poled lithium niobate. Simulation results show that the terahertz wave fo
rm analysis reproduces root-mean-square domain width fluctuations. (C) 2000
American Institute of Physics. [S0003-6951(00)02442-6].