Fabrication of periodic and quasi-periodic superlattices for nonlinear optical applications

Ferroelectric crystals with periodic and quasi-periodic domain structures, such as LiNbO/sub 3/, LiTaO/sub 3/, Sr/sub 0.6/Ba/sub 0.4/Nb/sub 2/O/sub 6/ and KTiOPO/sub 4/ optical superlattice crystals, have attracted great interest because of their promising properties for quasi-phase-matched (QPM) frequency conversion. Periodic or quasi-periodic reversal of the crystal domains compensates for a mismatch between the propagation speeds of the pump light and generated light along a particular crystallographic direction. This allows phase matching to be achieved for the highest nonlinear coefficients in a particular material. Second harmonic generation (SHG), third harmonic generation (THG) and optical parametric generation (OPG) experiments performed with these superlattices have produced wavelengths throughout visible and infrared spectra with CW and nanosecond, picosecond, femtosecond pulse duration in high conversion efficiencies. To meet the needs of various applications, the design and fabrication of these superlattices become the one of the focus of the research.