OPTICAL WAVEGUIDE AND ITS PRODUCTION, OPTICAL WAVELENGTH CONVERSION ELEMENT USING THIS OPTICAL WAVEGUIDE, SHORT WAVELENGTH LIGHT EMITTING DEVICE AND OPTICAL PICKUP

摘要

PROBLEM TO BE SOLVED: To enable the output of a second harmonic wave having an excellent light condensing characteristic and to increase the overlap of a basic wave on the second harmonic wave by providing an ion exchange layer with a refractive index larger than the refractive index of a waveguide and specific thickness. SOLUTION: The ion exchange layer (high-refractive index layer) 63 formed on the surface of the waveguide 62 on the surface of a crystalline substrate 61 has the refractive index larger than the refractive index of the waveguide 62 and the thickness at which the basic wave 64 propagating in the waveguide 62 cannot propagate the inside of the ion exchange layer 63 but the harmonic wave of the basic wave 64 can propagate the ion exchange layer 63. Namely, the thickness and refractive index of the high-refractive index layer 63 satisfy a cut-off condition for the basic wave 64. The thickness and refractive index of the high-refractive index layer 63 are merely so selected as to satisfy the cut-off condition for the basic wave 64 and a waveguide condition for the SHG wave in order to embody the wavelength conversion element of the high refractive index in the waveguide 62 having such high-refractive index layer 63.