PULSE NARROWING CHARACTERISTICS IN TRAVELING-WAVE OPTICAL PARAMETRIC GENERATION IN KTIOPO4 CRYSTALS

Pulse narrowing characteristics in traveling-wave optical parametric g eneration in KTiOPO4 crystals are investigated. By utilizing the pulse narrowing effect, output pulses with pulse duration of 250 fs can be obtained from 550 fs pump pulses in the experiment. It is also demonst rated that when the conversion efficiency becomes large by increasing the pump intensity or by changing the phase-matching angle, the pulse narrowing effect becomes small. These tendencies are confirmed by nume rical calculations of the parametric propagation process, which includ e the effects of temporal pulse shape, group-velocity difference, tran sverse beam profile, walk-off, two-photon absorption, and depletion. T he theoretical results indicate that when the conversion efficiency be comes greater than 1%, the back-conversion process becomes large at th e high-intensity part of the signal and idler pulses. This causes the pulse width to increase and reduces the pulse narrowing effect. (C) 19 96 American Institute of Physics.