Dielectric thin film-applied substrate and optical modulation element using the same

Abstract

A dielectric thin film-applied substrate capable of suppressing occurrence of cracks even when the film thickness of the lithium niobate film is made, e.g., equal to or larger than 1 μm. The dielectric thin film-applied substrate includes a single crystal substrate and a dielectric thin film which is made of c-axis oriented lithium niobate and epitaxially formed on a main surface of the single crystal substrate. The dielectric thin film has a twin crystal structure including a first and crystals existing at a position obtained by rotating the first crystal 180° centered on the c-axis. In pole figure measurement by an X-ray diffraction method, the ratio between a first diffraction intensity corresponding to the first crystal and a second diffraction intensity corresponding to the second crystal is equal to or higher than 0.5 and equal to or lower than 2.0. Distortions accumulated inside the lithium niobate film are alleviated and occurrences of cracks accompanying increases in the film thickness are suppressed.

Dependencies are inferred from the claim text.