| 摘要 |
A low voltage modulation signal can be realized while reducing reflection and radiation of a high frequency modulation signal in an optical modulator. The optical modulator includes an electrooptic effect element (2) having a signal electrode (20) and a ground electrode (21,22) thereupon each provided with a pad (200,210,220), and varying optical phase by the electrooptic effect and; a relay substrate (40) constituted of a dielectric wafer on which a coplanar waveguide connected to the signal electrode pad and the ground electrode pad on the electrooptic effect element is formed; and a connector (3) having a center conductor (30) and an external conductor (31) respectively connected to the coplanar waveguide of the relay substrate, and supplying a modulation signal of microwave band to the signal electrode of the electrooptic effect element, wherein, when the modulation signal includes a component of 30 GHz and a pad space between the signal electrode pad and the ground electrode pad of the electrooptic effect element is defined as S Ä mu mÜ and a pad height is defined as H Ä mu mÜ, the pad height is no greater than 300 and the relation is set as <DF>-0.002H<2> + 1.3H - 160 < S < 0.0025H<2> - 1.6H + 550 </DF> <IMAGE>
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