Enhanced Cerenkov SHG in planar proton-exchanged LiNbO3 waveguides reproducing a 1-D PBG

Second harmonic generation (SHG) in the Cerenkov configuration is investigated in planar proton-exchanged lithium-niobate waveguides where the use of a linear grating fabricated on top of the waveguide reproduces a 1-D photonic band-gap stucture. In such conditions the conversion efficiency is strongly enhanced, due to the high density of the fundamental guided mode in correspondence of the linear grating. Optimum parameters of the linear grating are determined for different waveguides in view of the fabrication of a very compact device for highly efficient frequency doubling.