Domain inversion in LiTaO3 using proton exchange followed by heat treatment

We report on fabrication of a first‐order periodically domain‐inverted structure in −Z‐cut LiTaO3 using proton exchange followed by heat treatment. The expansion of the domain inversion width can be suppressed within the first‐order intervals by shortening the heat‐treatment time. To perform this suppression, we propose quick heat treatment, which features rapid rising rate and short soak time. This technique was used to study the formation process and the expansion characteristics of domain inversion during heat treatment. This produced a periodically domain‐inverted structure with interval of 4 μm and depth of 1.8 μm over a 10 mm length in the LiTaO3. The potential for this structure was evaluated by examining the characteristics of a first‐order quasi‐phase‐matched second‐harmonic generation device with a proton‐exchanged waveguide. We also discuss the nucleation and expansion of domain inversion, based on experimental studies.