Quasi-phase-matched harmonic generation through coupled parametric processes in a quasiperiodic optical superlattice

We have investigated and fabricated an optical superlattice of LiTaO3, in w hich two building blocks, each containing a pair of antiparallel 180 degree s ferroelectric domains, were arranged as a Fibonacci sequence. The second- and third-harmonic generation in this structure have been studied and measu red. The results verifies that the second-harmonic spectrum and the third h armonic may be generated in a quadric nonlinear medium by a series of quasi -phase-matching processes. The experimental results are in good agreement w ith theory. (C) 1998 American Institute of Physics. [S0021-8979(98)03324-6] .