Efficiency improvement by high-index cladding in LiNbO/sub 3/ waveguide quasiphase-matched wavelength converter for optical communication

Quasi-phase-matched difference frequency generation devices for the 1.5-(mu)m band using a LiNbO/sub 3/ waveguide with a high-index cladding layer of As/sub 2/S/sub 3/ were designed and fabricated. By the cladding, the guided mode profiles were modified, and their overlap was increased. A high normalized conversion efficiency of 790%/W was obtained for 30-mm interaction length.