Ultraviolet Quasi-Phase-Matched Second Harmonic Generation in Surface Periodically Poled Lithium Niobate Optical Waveguides
A. C. Busacca, R. L. Oliveri, A. C. Cino, S. Riva-Sanseverino, A. Parisi and G. Assanto
Laser Phys. 17, 884-888 (2007)
Abstract:The compatibility of low concentration (alfa-phase) proton exchange channel waveguides with electric field surface periodic poling of congruent lithium niobate (SPPLN) crystals has been experimentally demonstrated. With such waveguides, we obtained ultraviolet second harmonic generation (SHG) by first order quasi-phase-matching (QPM), a result made possible by the fabrication, on Z-cut LN crystals, of periodic structures with a pitch down to 750 nm. Nonlinear copropagating QPM–SHG measurements have been carried out on such structures. The pump source was a Ti:sapphire laser with a tunability range of 700–980 nm and a 40 GHz linewidth. We have measured UV continuous wave light at 390 nm by means of a lock-in amplifier and a photodiode with an enhanced response in the UV. The measured conversion efficiency was about 1% W–1cm–2.