Patent ID: 9703169
Date: 2017-07-11
CPC Classifications: G02B,G02F,H04B,H04J

Claim:
1. An optical modulator, comprising: a waveguide substrate; and a multiplexing optical system, wherein the waveguide substrate includes: a first modulation portion having a first optical waveguide and a first modulation electrode for modulating light propagating through the first optical waveguide; a second modulation portion having a second optical waveguide different from the first optical waveguide and a second modulation electrode for modulating light propagating through the second optical waveguide; a first optical path being an optical waveguide connected to the first modulation portion, guiding light modulated by the first modulation portion along the first optical path and outputting from an output end; and a second optical path being an optical waveguide connected to the second modulation portion, guiding light modulated by the second modulation portion along the second optical path and outputting from the output end, the multiplexing optical system includes a first surface and a second surface opposite to the first surface, inputting first output light output from the first optical path and second output light output from the second optical path from different positions of the first surface and outputting after combining the first output light and the second output light at a combining point of the second surface, an optical path length between the first surface and the combining point in the first output light is larger than an optical path length between the first surface and the combining point in the second output light, an optical path length between the first modulation portion and the first surface and an optical path length between the second modulation portion and the first surface are different, positions where the first and second modulation portions are provided are different along a light guiding direction A that extends from output ends of the first and second modulation portions toward the first surface, an optical path length from a first modulation point at the output end of the first modulation portion to the combining point in the first output light is the same as an optical path length from a second modulation point at the output end of the second modulation portion to the combining point in the second output light, and a first condensing lens which condenses the first output light output from the optical modulating element and a second condensing lens which condenses the first output light output from the optical modulating element are provided between the optical modulating element and the multiplexing optical system, the first condensing lens and the second condensing lens being provided independently, wherein the first output light and the second output light are output in parallel toward a predetermined output direction, and within a waveguide surface on which the first and second optical waveguides are provided, 0°<θ<90° is satisfied assuming that an angle between the output end of the waveguide substrate and the predetermined output direction is θ.