Patent ID: 7916981
Filing Date: 2011-03-29
Classification: G02F

Abstract:
1. An optical modulator, comprising: a substrate having an electro-optic effect; an optical waveguide embedded in said substrate to have a light wave guided therein; and a traveling wave electrode mounted on said substrate to have a high frequency electric signal applied thereon so that said light wave is modulated by said high frequency electric signal with said electro-optic effect, said traveling wave electrode being constituted by a center electrode and ground electrodes; in which: said optical waveguide has first and second interaction optical waveguides to collectively form a Mach-Zehnder optical waveguide operative to modulate said light wave in a phase modulation manner under the condition that said high frequency electric signal is applied to said traveling wave electrode, and an optical input portion to have said light wave inputted therethrough, said first and second interaction optical waveguides collectively form a region where respective widths of said first and second interaction optical waveguides are different from each other, said first and second interaction optical waveguides are formed such that one of said first and second interaction optical waveguides has a spot-size larger than a spot-size of said light wave guided in the other of said first and second interaction optical waveguides, said first and second interaction optical waveguides are positioned such that a distance between said center electrode and a center of one of said first and second interaction optical waveguides having a larger spot-size is closer than a distance between said center electrode and a center of the other of said first and second interaction optical waveguides, to ensure that interaction efficiencies between said high frequency electric signal and said light wave guided in said respective first and second interaction optical waveguides are substantially equal to each other, and said first and second interaction optical waveguides are formed to respectively have widths different from said optical input portion such that one of said first and second interaction optical waveguides has a width narrower than said optical input portion while the other of said first and second interaction optical waveguides has a width wider than said optical input portion, and said first and second interaction optical waveguides are also formed to have taper portions to be connected with said optical input portion, respectively.