  Highly confining waveguides without degraded nonlinear coefficient and low
propagation losses have been fabricated in lithium niobate by a new process
that we called High Vacuum Vapor-phase Proton Exchange (HiVac-VPE). Index
contrast, index profile, nonlinearity and crystallographic phases are carefully
investigated. Original analysis of index profiles indicates that the waveguides
contains sub-layers whose depths are depending on the exchange durations.
Propagation behavior, propagation losses and Second Harmonic Generation (SHG)
response of HiVac-VPE channel waveguides are investigated at telecom
wavelength. The results recommend HiVac-VPE as very promising technique for
fabricating efficient nonlinear photonic integrated circuits in LN crystals.
