Waveguides of 5 mol% MgO-doped lithium niobate thin film are grown on a LiTaO3 substrate by liquid-phase epitaxy. The photorefractive sensitivity of the thin-film LiNbO3 waveguides using the Li2O-V2O5 flux and that of waveguides using Li2O-B2O3 flux are quantitatively measured and compared. The MgO-doped LiNbO3 thin-film waveguides grown using the Li2O-B2O3 flux are proven to be much more resistant to optical damage than those grown using the Li2O-V2O5 flux.

could not be measured by it. However, we found that they can be qualitatively measured by investigating In 2 O 3 grains formed by H 2 annealing with higher reactivity with InN and O 2 , using X-ray diffraction and PL spectroscopy. In this paper, we discuss the formation mechanism of InON alloy grains in InN films.

Using the liquid phase epitaxial growth (LPE) method, an LiNbO3 thin‐film optical waveguide was formed on LiNbaO3 substrate with MgO added at 5 mol percent. This is channelized by Ar plasma etching so that a ridged waveguide is created. the TM mode optical propagation loss of this waveguide is 1.2 dB/cm at wavelengths of 1.55 μm and 0.83 μm. By means of this waveguide, a Mach‐Zender‐type optical intensity modulator was designed. the operating voltage was compared with that in a modulator designed with a Ti‐diffused LiNbO3 waveguide. It was found that the electrooptic effect was approximately equal. Further, in the optical intensity modulator formed with traveling wave electrodes, the operating voltage was 4.6 V and the optical 3‐dB bandwidth was more than 6.5 GHz in the frequency measurement at a wavelength of 1.55 μm.