After forming domain inverted layers 3 in an LiTaO3 substrate
1, an optical waveguide is formed. By performing low-temperature annealing
for the optical wavelength conversion element thus formed, a stable proton exchange
layer 8 is formed, where an increase in refractive index generated during
high-temperature annealing is lowered, thereby providing a stable optical wavelength
conversion element. Thus, the phase-matched wavelength becomes constant, and variation
in harmonic wave output is eliminated. Consequently, with respect to an optical
wavelength conversion element utilizing a non-linear optical effect, a highly reliable
element is provided.
