Abstract: An optical modulator modulates light propagating in a three-dimensional optical waveguide 5 by applying a voltage on the waveguide. The modulator has a three dimensional optical waveguide 5 having at least a pair of branched portions 5b, 5c and a recombining portion 5f of the branched portions 5c, 5d and radiating light of off-mode, and a slab optical waveguide 4 guiding the light of off-mode. The modulator also has modulating electrodes 7A, 7B, 7C for applying a signal voltage and a direct current bias on the waveguide 5 to modulate light propagating in the waveguide 5. The modulator further has a photo detector 13 for detecting light radiated from the slab optical waveguide 4, and a controlling unit 15 for varying the direct current bias based on an output from the photo detector 13 so as to control the operational point of the modulator. According to the modulator, the operational point may be controlled with improved efficiency and stability.

Abstract: An object of the present invention is to improve the modulation efficiency of an optical modulator in a high frequency band while satisfying the velocity matching condition. An optical modulator is provided having an optical waveguide for propagating light, an electrode for applying a voltage on the waveguide for modulating the light, a signal source electrically connected to the electrode and a terminating resistance electrically connected to the electrode. The signal source has a characteristic impedance Zi and the terminating resistance has an impedance Zl satisfying the formula (Zi<Zl). Alternatively, the signal source has a characteristic impedance Zi and the electrode has a characteristic impedance Zc satisfying the formula (Zi<Zc).

Abstract: Major surface of a substrate having an optical waveguide and a modulation electrode is pasted to a base substrate through a thermosetting resin, and then the rear surface of the substrate is machined thus making thin the entirety. Subsequently, the rear surface of the substrate thus rendered thin is subjected to machining or laser machining to form a thin part, which is further subjected to machining or laser machining to form a first thin part at a part, including the optical waveguide, of the thin part and a second thin part thinner than the first thin part contiguously thereto. Thereafter, the rear surface of the substrate is pasted to the major surface of a supporting substrate through a thermosetting resin and the base substrate is stripped thus obtaining an optical modulator.

Abstract: An optical waveguide device 1 has an optical waveguide substrate 19, a supporting body 2 for supporting the substrate 19 and a joining layer 3 for joining the substrate 19 and the supporting body 2. The substrate 19 has a flat plate-shaped main body 4 made of an electro-optic material with a thickness of 30 &mgr;m or smaller and having first and second main faces 4a and 4b opposing each other, an optical waveguide provided on the side of the first main face 4a of the main body 4, and electrodes 7A to 7C provided on the side of the first main face 4a of the main body 4. The joining layer 3 joins the supporting body 2 at a joining face 4d and the second main face 4d of the main body 4. The joining face 2a of the supporting body 2 is substantially flat. Alternatively, the joining layer 3 has a thickness of 200 &mgr;m or lower.

Abstract: An optical waveguide device has an optical waveguide substrate and a supporting substrate. The optical waveguide substrate has a main body made of an electro-optic material and having a first main face and a second main face, an optical waveguide formed in or on the main body and an electrode formed on the side of the first main face of the main body. The supporting substrate is joined with the second main face of the main body. A low dielectric portion with a dielectric constant lower than that of the electro-optic material is formed in the supporting substrate.

Abstract: A Mach-Zehnder optical waveguide is disposed in a substrate made of a material having an electro-optic effect. Coplanar-waveguide modulating electrodes are disposed on a principal surface of the substrate. A dielectric layer is disposed on a reverse surface of the substrate. A supporting substrate having a recess is disposed in contact with the dielectric layer such that the recess is located at a position corresponding to a modulating region. The relationship: &egr;r>&egr;s is satisfied where &egr;r represents the dielectric constant of the supporting substrate and &egr;s represents the dielectric constant of the dielectric constant of solid, liquid, or gaseous substance in the recess.

Abstract: An object of the invention is to provide an electrode system for optical modulation of an optical modulator to reduce a thickness “E” of an electrode required for velocity matching and for reducing a propagation loss in the electrode. A substrate 2 is made of an electrooptic material and has one and the other main faces 2a, 2b opposing each other. An electrode system 20A is provided on the substrate 2 for applying a voltage for modulating light propagating in optical waveguides 6A and 6B. The electrode system 20A includes ground electrodes 3A, 3B and a signal electrode 4. A ratio “W/G” of a width “W” of the signal electrode 4 to a gap “G” between the ground and signal electrodes is 0.8 or higher. Preferably, the substrate 2 has a thickness “T” of 20 &mgr;m or larger, in a region where the optical waveguides 6A and 6B are provided.

Abstract: An optical waveguide device 1A has a substrate 22 and a supporting body 10 for supporting the substrate. The substrate 22 has a main body 2 made of an electrooptic material and one and the other main faces, optical waveguides 3a, 3b and electrodes 4B, 4C provided on the side of the one main face 2a of the main body 2 The supporting body 10 is joined with the substrate 2 on the side of the other main face, and the electrode has a feedthrough portion. The device 1A further has a low dielectric portion 7 provided under the feed through portion and between the other main face 2b of the main body 2 and the supporting body 10.

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 when viewed in the cross section of the modulating region. 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 between the adjacent thicker parts.

Abstract: An optical member-bonding structure includes a first optical component, a second optical component, and an integral substrate having a mounting face on which the first and second optical components are mounted, at least the first optical member being bonded to the integral substrate, wherein a bonding face of the first optical member is bonded to the mounting face of the integral substrate with a cured and shrunk optical adhesive in such a state that an optical axis of the first optical member is aligned with that of the second optical member at a precision of not more than 1 &mgr;m, a groove is formed in a such bonding region of that mounting face of the integral substrate as being bonded with the first optical member, and at least part of the optical adhesive is filled into the groove.

Abstract: An optical modulator modulates light propagating in a three-dimensional optical waveguide 5 by applying a voltage on the waveguide. The modulator has a three dimensional optical waveguide 5 having at least a pair of branched portions 5b, 5c and a recombining portion 5f of the branched portions 5c, 5d and radiating light of off-mode, and a slab optical waveguide 4 guiding the light of off-mode. The modulator also has modulating electrodes 7A, 7B, 7C for applying a signal voltage and a direct current bias on the waveguide 5 to modulate light propagating in the waveguide 5. The modulator further has a photo detector 13 for detecting light radiated from the slab optical waveguide 4, and a controlling unit 15 for varying the direct current bias based on an output from the photo detector 13 so as to control the operational point of the modulator. According to the modulator, the operational point may be controlled with improved efficiency and stability.

Abstract: An optical waveguide element includes a substrate made of a lithium tantalate single crystal or a lithium niobate-lithium tantalate solid solution single crystal and a bulky optical waveguide made of a lithium niobate single crystal is directly joined to the substrate. The c-axis of the single crystal substrate is tilted at an angle with respect to the surface of the substrate to which the bulky optical waveguide is joined. The tilted angle is preferably within a range of 17-37 degrees.

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 traveling wave optical modulator includes an optical waveguide substrate made of an electro-optic and ferrodielectric single crystal in the form of an X- or Y-orientation plate_and comprising a thicker portion having a larger thickness and a thinner portion having a smaller thickness; first and second branched optical waveguide portions formed at least on the thinner portion of the optical waveguide substrate; a set of electrodes provided on at least the thinner portion of the substrate and adapted for applying voltage to the first and second optical waveguide portions to modulate a light propagating the optical waveguide portions; and a buffer layer provided to cover a part of the optical waveguide portions at the thinner portion of the substrate, the electrodes crossing on the buffer layer.

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: A bonding structure of optical members has a first optical member, a second optical member, a first support member supporting the first optical member, and a second support member supporting the second optical member. The first support member is bonded to the second support member. The first support member and the second support member are bonded with each other via a hardened acrylic resin adhesive under a condition such that an optical axis of the first optical member and an optical axis of the second optical member are optically aligned with each other with an accuracy of within 1 &mgr;m. A viscosity of the acrylic resin adhesive before hardening is larger than 500 cP and lower than 5000 cP.

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: An optical member-bonding structure includes a first optical component, a second optical component, and an integral substrate having a mounting face on which the first and second optical components are mounted, at least the first optical member being bonded to the integral substrate, wherein a bonding face of the first optical member is bonded to the mounting face of the integral substrate with a cured and shrunk optical adhesive in such a state that an optical axis of the first optical member is aligned with that of the second optical member at a precision of not more than 1&mgr;m, a groove is formed in a such bonding region of that mounting face of the integral substrate as being bonded with the first optical member, and at least part of the optical adhesive is filled into the groove.