Efficiency improvement by high-index cladding in LiNbO3 waveguide quasi-phase-matched wavelength converter for optical communication

Quasi-phase-matched difference frequency generation devices for the 1.5-μm band using a LiNbO
₃
waveguide with a high-index cladding layer of As
₂
S
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.