A NOVEL QUASI-PHASE-MATCHING FREQUENCY-DOUBLING TECHNIQUE

A new quasi-phase-matching technique for efficient second-harmonic gen eration is reported. It is based on the spatial periodic modulation of the light intensity along the propagation direction, rather than the conventional spatial periodic modulation of the nonlinear optical coef ficients. It can be realized by using a novel dual-channel waveguide f requency doubler structure for the desired light intensity distributio n. This dual-channel waveguide device has major advantages including v ery small beam size, high light intensity within long nonlinear-wavegu ide interaction length, highly efficient second-harmonic generation, e ase in fabrication of the nonlinear channel waveguides without any spa tially periodic poling, and low waveguide propagation losses, The new quasi-phase-matching technique can also be applied to third-harmonic g eneration and other nonlinear optics processes. (C) 1998 Elsevier Scie nce B.V. All rights reserved.