| 摘要 |
The present invention provides an optical switch, an optical modulator, and a wavelength variable filter each of which has a simple configuration, which requires only a low driving voltage, which is independent of polarization, and which can operate at high speed. An optical switch according to the present invention includes a 3-dB coupler ( 16 ) placed on an output, a 3-dB coupler ( 17 ) placed on an output, and two optical waveguides connecting the input-side 3-dB coupler and the output-side 3-dB coupler together. The optical switch also includes a phase modulating section ( 18 ) that applies electric fields to one or both of the two optical waveguides. At least two optical waveguides are a crystal material including KTa<SUB>x</SUB>Nb<SUB>1-x</SUB>O<SUB>3 </SUB>(0<X<1) AND K<SUB>x</SUB>Li<SUB>1-x</SUB>Ta<SUB>y</SUB>Nb<SUB>1-y</SUB>O<SUB>3 </SUB>(0<x<1, 0<Y<1), OR KTA<SUB>x</SUB>Nb<SUB>1-x</SUB>O<SUB>3 </SUB>or K<SUB>x</SUB>Li<SUB>1-x</SUB>Ta<SUB>y</SUB>Nb<SUB>1-y</SUB>O<SUB>3</SUB>.
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