| 摘要 |
PROBLEM TO BE SOLVED: To fully secure the optical damage resisting strength of a single crystal, restraining increase in the coercive electric field, and holding down variations in the characteristics, when forming a cyclic polarization reverse structure. SOLUTION: A lithium tantalate single-crystal substrate of congruent composition, which contains magnesium oxide as an additive, the addition amount being set in a range of 0 mol% to 0.15 mol%, is used, and the lithium tantalate single crystal substrate of congruent composition is treated with raw material, at least containing lithium according to a vapor-phase balance method to approach a stoichiometric composition. The substrate 1 is used to form the optically functional element. COPYRIGHT: (C)2009,JPO&INPIT
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