Abstract: A comb electrode 3 is provided on a first main face 2a and a uniform electrode 4 is provided on a second main face 2b of a substrate made of a ferroelectric single crystal of a single domain, and a voltage is applied on the comb electrode 3 and the uniform electrode 4 to produce domain inversion part. It is laminated, on the substrate, an underlying substrate comprising a main body 5, a first conductive film 6 provided on a first main face 5a and a second conductive film 7 provided on a second main face 5b of the main body 5. The uniform electrode 4 is electrically conducted with the first conductive film 6 and a voltage is applied on the comb electrode 3 and the second conductive film 7 to form a domain inversion part in the substrate 2.

Abstract: The present invention provides an optical waveguide device having a configuration such that the optical waveguide is folded back on an end area of the optical waveguide substrate to widen the modulation band. The optical waveguide device includes a substrate body made of an electro-optical material, optical waveguide, and modulation electrodes for applying a voltage on the optical waveguide. The optical waveguide includes first primary areas, a first curved area, first folding-back areas provided between the first curved area and a folding-back point, second primary areas, a second curved area, and second folding-back areas provided between the second curved area and the folding-back point. At least a part of the signal electrode is provided in a folding-back region extending from the first curved area and the second curved area to the folding-back point.

Abstract: An optical functional device comprises a dielectric substrate 5, a ferroelectric thin layer 10 provided on the dielectric substrate 5 and comprising a material having electro-optical effect and an electrode 3A, 3B provided on the ferroelectric thin layer 10. A part of the ferroelectric thin layer 10 functions as a core 9 of the optical wave guide and the dielectric substrate functions as a clad for the optical waveguide. The optical waveguide 9 constitutes a multi-mode waveguide in the direction “D” of depth of the ferroelectric thin layer.

Abstract: It is provided an optical waveguide device in which the radius of curvature of a curved part of an optical waveguide can be lowered and the radiation loss of light in the curved part can be reduced. An optical waveguide device 2 has a ferroelectric optical waveguide substrate and an optical waveguide 5 formed in or on the substrate and modulating electrodes 4A, 4B and 4C. The thickness of the optical waveguide substrate is 30 ?m or smaller at least in a region where the optical waveguide is formed. The optical waveguide has curved part having a radius of curvature of 30 mm or smaller.

Abstract: A first main face 1a of a substrate 1 of a dielectric single crystal is etched to form recesses 4 in the substrate 1. A second main face 1b of the substrate 1 is mechanically processed to form a slab 10, so that the recesses 4 pass through the substrate 1 to form through holes 11.

Abstract: An optical functional device 1 has a slab type two-dimensional photonic crystal layer 29. The layer 29 has a dielectric layer 4 and a plurality of lattice columns 5 each comprising dielectric pillars. A waveguide portion 6 is provided in the photonic crystal layer 29. A ground electrode 8 and a signal electrode 9 are formed on the dielectric layer 4 for applying a modulating voltage on light propagating in the waveguide portion 6. A layer 2 of a high dielectric constant is laminated on the dielectric layer 4. A low dielectric portion is formed direct under the waveguide portion 6 and the lattice columns 7a, 7B and 7C of at least first, second and third orders in distance with respect to said waveguide portion.

Abstract: An optical modulator is provided for modulating light propagating in a three-dimensional optical waveguide 5 by applying a voltage thereto. The optical modulator has the three-dimensional optical waveguide 5 including at least one pair of branch optical waveguides 5c and 5d, a multiplexing part 5e of the branch optical waveguides and an emission part 5f provided in the downstream of the multiplexing part, modulation electrodes 3A, 3B and 4 for applying a signal voltage for modulating light propagating in the three-dimensional optical waveguide 5, and guiding waveguides 6A and 6B for guiding primary mode light from the multiplexing part. Thickness of the substrate is 20 ?m or less at least under the modulation electrodes, and an operation point of the optical modulator is controlled by changing, based on light output from the guiding waveguides, DC bias applied onto the modulation electrodes.

Abstract: An optical waveguide structure has a slab type photonic crystal and an optical waveguide provided in the photonic crystal. The photonic crystal has a slab of a dielectric film and a plurality of lattice columns each having dielectric pillars. The dielectric pillars included in the lattice columns at least in n'th order (n represents 1, 2, 3, 4 and 5) in distance with respect to said optical waveguide, respectively, has a planar shape of an equilateral polygon or exact circle. At least one of the dielectric pillars included in the lattice columns at least in n'th order (n represents 2, 3, 4 and 5) with respect to the optical waveguide has a size rn different from a fundamental size ro.

Abstract: When a domain inversion part is produced by means of electric field polling process, damage in the vicinity of the forward end of a comb electrode and deviation of width of each domain inversion part are to be reduced. A polarization domain inversion structure has polarization domain inversion parts is produced by electric field poling process using a comb electrode formed on one surface of a substrate of a ferroelectric single crystal and of a single domain, and the comb electrode has a plurality of electrode portions and feeding portion. Each of the electrode portions corresponds with each domain inversion part of the domain inversion structure. The electrode portion has a plurality of low resistance pieces arranged in a direction “F” intersecting the longitudinal direction “E” of the electrode portion and spaced apart with each other.

Abstract: In a piezoelectric thin film device of the present invention, the degree of flexibility is enhanced in selection of a piezoelectric material constituting a piezoelectric thin film and the crystal orientation in the piezoelectric thin film. A piezoelectric thin film filter, including four film bulk acoustic resonators, has a configuration where a filter section for providing a filter function of the piezoelectric thin film filter is bonded with a flat base substrate mechanically supporting the filter section via an adhesive layer. In manufacturing of the piezoelectric thin film filter, a piezoelectric thin film is obtained by performing removal processing on a piezoelectric substrate, but the piezoelectric thin film obtained by removal processing cannot independently stand up under its own weight. For this reason, a prescribed member including the piezoelectric substrate is previously bonded to the base substrate as a support prior to the removal processing.

Abstract: The present invention is directed to preventing characteristic variations and damage caused by a difference in thermal expansion coefficient. A piezoelectric thin film filter, including four film bulk acoustic resonators, has a configuration where a filter section for providing a filter function of the piezoelectric thin film filter is bonded with a flat base substrate mechanically supporting the filter section via an adhesive layer. In manufacturing of the piezoelectric thin film filter, a piezoelectric thin film is obtained by performing removal processing on a piezoelectric substrate that can individually stand up under its own weight, but substrates made of one kind of single crystal material are adopted as the base substrate and the piezoelectric substrate, to make the respective thermal expansion coefficients of the piezoelectric thin film and the base substrate coincident with each other.

Abstract: The present invention is directed to improving characteristics of a piezoelectric thin film device. A piezoelectric thin film filter including four film bulk acoustic resonators has a configuration where a filter section and a base substrate are bonded to each other via an adhesive layer, the filter section including a piezoelectric thin film which cannot stand up individually under its own weight, the flat base substrate mechanically supporting the filter section. As a piezoelectric material constructing the piezoelectric thin film, it is desirable to use a single-crystal material including no grain boundary, selected from crystal, lithium niobate, lithium tantalite, lithium tetraborate, zinc oxide, potassium niobate, and langasite.

Abstract: An optical functional device comprises a dielectric substrate 5, a ferroelectric thin layer 10 provided on the dielectric substrate 5 and comprising a material having electro-optical effect and an electrode 3A, 3B provided on the ferroelectric thin layer 10. A part of the ferroelectric thin layer 10 functions as a core 9 of the optical wave guide and the dielectric substrate functions as a clad for the optical waveguide. The optical waveguide 9 constitutes a multi-mode waveguide in the direction “D” of depth of the ferroelectric thin layer.

Abstract: It is provided an optical waveguide device in which the radius of curvature of a curved part of an optical waveguide can be lowered and the radiation loss of light in the curved part can be reduced. An optical waveguide device 2 has a ferroelectric optical waveguide substrate and an optical waveguide 5 formed in or on the substrate and modulating electrodes 4A, 4B and 4C. The thickness of the optical waveguide substrate is 30 ?m or smaller at least in a region where the optical waveguide is formed. The optical waveguide has curved part having a radius of curvature of 30 mm or smaller.

Abstract: It is provided a novel method of producing polarization inversion parts by electric field polling process wherein the polarization inversion part extends to a deeper point from the surface of a substrate. The polarization inversion part is produced by electric field polling process using a comb electrode having a plurality of electrode portions 5 and a feeding portion 1. Each electrode portion 5 has a base portion 6 extending from the feeding portion 1 and a plurality of conductive portions 5a, 5b and 5c separated from the base portions 6, and the conductive portions have an average length “d” of 4 ?m or longer and 9 ?m or shorter. Alternatively, each electrode portion 5 has a base portion 6 extending from the feeding portion 1 and a plurality of conductive portions 5a, 5b and 5c separated from the base portion 6, and the conductive portion 5b at the tip end of the electrode portion has a length “db” smaller than the length “da” of the conductive portion 5b nearest to the base portion.

Abstract: A comb electrode 3 is provided on a first main face 2a and a uniform electrode 4 is provided on a second main face 2b of a substrate made of a ferroelectric single crystal of a single domain, and a voltage is applied on the comb electrode 3 and the uniform electrode 4 to produce domain inversion part. It is laminated, on the substrate, an underlying substrate comprising a main body 5, a first conductive film 6 provided on a first main face 5a and a second conductive film 7 provided on a second main face 5b of the main body 5. The uniform electrode 4 is electrically conducted with the first conductive film 6 and a voltage is applied on the comb electrode 3 and the second conductive film 7 to form a domain inversion part in the substrate 2.