| 摘要 |
PROBLEM TO BE SOLVED: To improve a yield and to make temperature tuning width narrow. SOLUTION: This birefringent filter (10) includes an optical element (14) with transmission different in accordance with a polarization direction and SLT birefringent crystal (15) using lithium tantalate (LiTaO3) having a stoichiometric composition, and the birefringent filter (10) is inserted into an optical resonator (17). As a result, since wavelength tuning width determined by the lithium tantalate (SLT) having the stoichiometric composition is larger than wavelength tuning width determined by the conventional yttrium vanadate (YVO4), the SLT birefringent crystal (15) can be made thick. Therefore, the allowable error of a thickness becomes large, precision required for working is made lower, and a yield can be improved. Since temperature-wavelength change rate is high in the SLT birefringent crystal (15), temperature tuning width can be made narrow. COPYRIGHT: (C)2009,JPO&INPIT
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