ND-YVO4 LASER MODE-LOCKED BY CASCADING OF 2ND-ORDER NONLINEARITIES

Experimental results on an end pumped CW Nd:WO, laser mode locked usin g cascading of second order nonlinearities in an intracavity KTP cryst al are reported. The mode locking technique exploits the nonlinear tra nsverse phase distortion arising during second harmonic generation and parametric back conversion and is demonstrated for the first time wit h a type II phase matched nonlinear crystal (KTP). Pulses of 6.8 ps ha ve been obtained. For compensation of the group velocity mismatch in t he nonlinear crystal a technique, whose effectiveness was previously o nly proved in combination with type I phase matching, has been demonst rated to be also successfully applicable with type II phase matching. This technique is based on the use of an intracavity birefringent crys tal. The compensation method has also been applied to the same laser m ode locked by the nonlinear mirror technique and pulses of comparable duration have been obtained. (C) 1998 Elsevier Science B.V. All rights reserved.