Optical modulator having element for varying optical phase by electrooptic effect

An optical modulator comprising:

• an electrooptic effect element having a signal electrode and a ground electrode thereupon each provided with a pad, and varying optical phase by the electrooptic effect and;
• a relay substrate 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 having a center conductor and an external conductor 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 40 GHz and a pad space between the signal electrode pad and the ground electrode pad of the electrooptic effect element is defined as S [μm] and a pad height is defined as H [μm], the pad height is no greater than 300 and the relation is set as
• −0.002H2+1.3H−160<S<0.001H2−0.8H+370

An optical modulator comprising:

• an electrooptic effect element having a signal electrode and a ground electrode thereupon each provided with a pad, and varying optical phase by the electrooptic effect and;
• a relay substrate 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 having a center conductor and an external conductor 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 characteristic impedance by the signal electrode pad and the ground electrode pad of the electrooptic effect element is defined as Z0 [Ω] and a pad height is defined as H [μm], the pad height is no greater than 300 and the relation is set as
• −0.0005H2+0.32H−19<Z0<0.00061H2−0.34H+98

An optical modulator comprising:

• an electrooptic effect element having a signal electrode and a ground electrode thereupon each provided with a pad, and varying optical phase by the electrooptic effect and;
• a relay substrate 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 having a center conductor and an external conductor 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 40 GHz and a characteristic impedance by the signal electrode pad and the ground electrode pad of the electrooptic effect element is defined as Z0 [Ω] and a pad height is defined as H [μm], the pad height is no greater than 300 and the relation is set as
• −0.0005H2+0.32H−19<Z0<0.000093H2−0.061H+57