Abstract: A travelling wave-type optical modulator has a substrate made of an electro-optic material, optical waveguides fabricated on the top surface of the substrate, and electrodes for modulating an optical wave through the optical waveguide. The substrate is partially thinned from the bottom surface of the substrate to form a first thinned portion and a second thinned portion so that the thickness of the first thinned portion is set to be larger than the thickness of the second thinned portion, and the optical waveguide is positioned in the first thinned portion.

Abstract: An optical waveguide device 1A has an optical waveguide substrate 15A and a supporting body 8 for supporting the substrate 15A. The substrate 15A has a main body 2 made of an electrooptic material and having a main face 2a and an opposing face 2b, optical waveguides 4A, 4B, and electrodes 3A, 3B, 3C for applying an electrical signal on the optical waveguides. At least a part of the opposing face 8a of the supporting body 8 opposing the substrate 15A is covered with a conductive layer 7A. It is thus possible to reduce the resonance due to substrate radiation of microwave into the whole of the optical waveguide substrate and supporting body.

Abstract: An optical device comprises a core layer; a first clad layer, with the core layer being deposited on a part of surface of the first clad layer; a second clad layer, with the core layer being provided between the first clad layer and the second clad layer; a third clad layer deposited on the second clad, an electrode for heating, and a substrate having a heat-sink function. At least one of the core layer and the clad layers comprises a material having a positive refractive index variation coefficient. The third clad layer has a refractive index smaller than that of the second clad layer.

Abstract: The spot size of light propagating through a cross waveguide 22 is larger than the spot size of light propagating through optical input waveguides 21a and 21b, optical output waveguides 23a and 23b, or connection waveguides 24a, 24b, 25a and 25b.

Abstract: An optical waveguide device 1A has an optical waveguide substrate 10A and a supporting substrate 6 supporting the substrate 10A. The substrate 10A has a main body 4 made of an electrooptic material and having first main face 4a and a second main face 4b, an optical waveguide 3 formed in or on the main body 4 and an electrode 2A, 2B or 2C formed on the side of the first main face 4a of the main body 4. The supporting substrate 6 is joined with the second main face 4b of the main body 4. A low dielectric portion 11 with a dielectric constant lower than that of the electrooptic material is formed in the supporting substrate 6.

Abstract: A travelling wave-type optical modulator has a substrate made of an electro-optic material, optical waveguides fabricated on the top surface of the substrate, and electrodes for modulating an optical wave through the optical waveguide. The substrate is partially thinned from the bottom surface of the substrate to form a first thinned portion and a second thinned portion so that the thickness of the first thinned portion is set to be larger than the thickness of the second thinned portion, and the optical waveguide is positioned in the first thinned portion.

Abstract: A travelling wave-type optical modulator has a supporting substrate and a ferroelectric single crystalline layer on the supporting substrate. The ferroelectric single crystalline layer has thicker parts and thinner parts within the modulating region of the travelling wave-type optical modulator as viewed in the cross section of the modulating region. Then, an optical waveguide is formed in the thicker part of the ferroelectric single crystalline layer, and electrodes for modulation are provided on the thinner part of the ferroelectric single crystalline layer in between the adjacent thicker parts.

Abstract: An optical waveguide element is disclosed, which includes a three-dimensional optical waveguide of a bulky non-linear optical crystal, a substrate, and a joining layer made of an amorphous material through which the substrate is joined to the optical waveguide.

Abstract: An optical control device include a substrate having an electrooptic effect, the substrate having ridges with optical waveguides. A buffer layer is formed on the substrate surface, and electrodes are provided. The electrodes includes at least one ground electrode, and a central electrode that is formed on the buffer layer over a ridge. The width of the central electrode on the side where the central electrode contacts the buffer layer is larger than the width of the optical waveguide. Because of this construction, the optical control device can achieve constant characteristics and a broad bandwidth.

Abstract: An optical functional device includes a semiconductor substrate, an optical functional layer provided on said semiconductor substrate and selected from the group consisting of a light emitting layer, a light absorbing layer, and an optical waveguide layer. The optical functional layer has a multi-quantum well layer. Preferably, the semiconductor substrate is a nonplanar semiconductor substrate having a ridge and two grooves adjacent said ridge, said ridge having a ridge width of from 1 to 10 .mu.m, a ridge height of from 1 .mu.m to 5 .mu.m, and a gap distance of from 1 .mu.m to 10 .mu.m. Such an optical functional device can be fabricated by growing, on a nonplanar semiconductor substrate having a specified dimension of the ridge, a strained multi-quantum well layer by metalorganic vapor phase epitaxy. Integrated optical device or circuit preferably includes an optical functional device on the nonplanar semiconductor substrate of a specified range of ridge shape factors.

Abstract: An optical functional device includes a semiconductor substrate, an optical functional layer provided on said semiconductor substrate and selected from the group consisting of a light emitting layer, a light absorbing layer, and an optical waveguide layer. The optical functional layer has a multi-quantum well layer. Preferably, the semiconductor substrate is a nonplanar semiconductor substrate having a ridge and two grooves adjacent said ridge, said ridge having a ridge width of from 1 to 10 .mu.m, a ridge height of from 1 .mu.m to 5 .mu.m, and a gap distance of from 1 .mu.m to 10 .mu.m. Such an optical functional device can be fabricated by growing, on a nonplanar semiconductor substrate having a specified dimension of the ridge, a strained multi-quantum well layer by metalorganic vapor phase epitaxy. Integrated optical device or circuit preferably includes an optical functional device on the nonplanar semiconductor substrate of a specified range of ridge shape factors.

Abstract: An electrically controlled optical device effective index includes a traveling wave electrode, a shield conductor and a thick buffer layer of a low dielectric constant. The thickness of an overlaid layer disposed between the traveling wave electrode and the shield conductor as well as the thickness of the buffer layer is so determined that an effective index of a microwave transmitted through the traveling wave electrode approaches an effective index of light transmitted through an optical waveguide, and that a microwave conductor loss is reduced, and that a characteristic impedance of said traveling wave electrode approaches a characteristic impedance of an associated external microwave circuit.

Abstract: An electrically controlled optical device includes a traveling wave electrode structure, a shield conductor and a thick buffer layer having a low dielectric constant. The thickness of an overlaid layer disposed between the traveling wave electrode structure and the shield conductor, as well as the thickness of the buffer layer, is determined so that the effective index of a microwave transmitted through the traveling wave electrode structure approaches the effective index of light transmitted through an optical waveguide, so that the microwave conductor loss is reduced, and so that the characteristic impedance of the traveling wave electrode structure approaches the characteristic impedance of an associated external microwave circuit.