US 4,709,978 AGranted

Mach-Zehnder integrated optical modulator

AssigneeBell Communications Research, Inc.

InventorJanet L. Jackel

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Abstract

A Mach-Zehnder interferometric modulator includes on a Z-cut crystal substrate of LiNbO.sub.3 an input waveguide section (302), an input branching section (303) for dividing an optical signal on the input waveguide into two substantially equal portions, first and second branch waveguides (304, 305) each having an electrode associated therewith (309, 308), an output branching section (306) for recombining the light from each branch waveguide into a single optical signal on an output waveguide section (307). The two branch waveguides are spaced close enough to maximize the field overlap between the applied electrical field and the optical field in the waveguides but are optically decoupled to prevent cross-coupling of light between the branches. This decoupling is achieved by using structures which change the propagation constant of one of the branches with respect to the other along the modulation length.

Claims9

Dependent claims

An optical interferometric modulator comprising

an input waveguide section
an input branching section for dividing an optical signal on said input section into two substantially equal portions,
first and second branch waveguides for transmitting the two portions of the divided optical signal,
first and second electrodes each associated with said first and second branch waveguides, respectively, and each in a proximate physical relationship with its associated branch waveguide along a modulation length,
an output branching section for combining the optical signals on said first and second branch waveguides, characterized in that
said first and second branch waveguides are disposed in such a proximate physical relationship with each other along the modulation length to maximize the field overlap between the electric fields from said first and second electrodes and the optical field in the branch waveguides, and
said modulator further comprises means for optically decoupling said first and second branch waveguides.

4 more elements

Dependencies are inferred from the claim text.