Abstract: The present invention provides an optical modulator, a method of manufacture therefore, and an optical communications system including the optical modulator. The optical modulator may include a substrate, a waveguide located within the substrate and electrodes located over the substrate. Additionally, the waveguide includes a first doped region and a second doped region that overlaps the first doped region and is located adjacent an outer surface of the substrate and the electrodes.

Abstract: An optical modulator has a dielectric buffer layer extending over an optical waveguide and extending under an electrode which applies an electric field through the dielectric buffer layer to the optical waveguide for causing the optical waveguide to vary in refractive index profile in linear-proportion to an intensity of the electric field thereby causing a phase shift of a light which is on propagation in the optical waveguide, wherein the dielectric buffer layer varies in thickness whereby an overlap integral of a profile of the electric field and an optical mode field profile at a thinner portion of the dielectric buffer layer is larger than that at a thicker portion of the dielectric buffer layer, and whereby a difference of an effective microwave refractive index from an optical refractive index at the thicker portion is smaller than that at the thinner portion.

Abstract: In an optical waveguide type device, an optical waveguide is formed in a crystal substrate having an electro-optical effect. A buffer layer is formed on the crystal substrate. Further, an signal electrode is formed on the buffer layer so that microwave signals are given to the signal electrode. In addition, a dielectric substrate is formed under the crystal substrate. With this structure, a groove is formed in the dielectric substrate and below at least the signal electrode. In this case, the groove functions as the air gap for reducing an attenuation of the microwave signals. According to this invention, the microwave attenuation is reduced and further the handling of the chip becomes easy. Alternatively, such a reduction can be accomplished by selecting a first width of an active portion of a signal electrode, a second width of a feeder portion of the signal electrode, and a third width of a connector. Specifically, the second width is wider than the first width and is narrower than the third width.

Abstract: A connector is provided for connecting to a pad of a signal electrode selectively formed over a dielectric buffer layer which extends over a crystal substrate of an optical device wherein a recess is selectively formed in an upper region of the crystal substrate so that the recess is positioned in the vicinity of the pad. The dielectric buffer layer and the signal electrode are not formed over the recess so that the connector is received securely in the recess whereby a side face of the connector is made into directly contact with a side face of the pad, and a top of the connector has substantially the same level as a top of the pad to allow a majority of microwave to travel between top surface regions of the pad and the connector without substantial loss.

Abstract: In an optical waveguide device which is typically for use as a waveguide modulator or switch and comprises a substrate exhibiting an electrooptic effect, an input and an output waveguide, first and second phase shift waveguides, a dielectric buffer layer on the substrate and the input, the output, and the phase shift waveguides, and a signal electrode and a ground electrode on the buffer layer to overlie on the phase shift electrodes and which may further comprise an additional ground electrode to form a CPW structure rather than an ASL or an ACPS structure, the buffer layer has a thickness which decreases continuously or stepwise from an outer edge to an inner edge of each of the first and the second waveguides. Preferably, a ratio of a thin thickness at the inner edges to a predetermined thickness at the outer edges and outwardly thereof is between 0.25 to 0.9.

Abstract: At least one waveguide 2,3,4 are formed on a crystal substrate 1 having an electro-optical effect. A buffer layer 5 (with a dielectric constant of 1.1 to 40) is formed on the waveguide. Lower CPW electrode structures 6,7 are formed on the buffer layer. Intermediate electrode structures 8,9 are formed thereon and additional electrode structure 10 is formed on the intermediate signal electrode 8.