Sumitomo Osaka Cement Co., Ltd.

National Institute for Materials Science

National Institute of Information and Communications Technology, Incorporated

Futoshi Yamamoto

Junichiro Ichikawa

Satoshi Oikawa

Kenji Kitamura

Sunao Kurimura

Katsutoshi Kondou

Yuhki Kinpara

Takashi Shinriki

Masahiro Tsuchiya

Tetsuya Kawanishi

Ryo Shimizu

Yoshihiro Hashimoto

Masayuki Izutsu

Kaoru Higuma

Shunji Takekawa

Shingo Mori

Hirotoshi Nagata

Masaru Nakamura

Yasuyuki Miyama

A method for forming a ferroelectric spontaneous polarization reversal in a desired region of a ferroelectric substrate includes the steps of forming, for the desired region of the surface of the ferroelectric substrate, an electrode pattern or a mask pattern composed of aggregates of micropatterns, and then applying a given voltage into the desired region. The configuration of the micropatterns can be a stripe-shaped pattern, an ellipse-shaped pattern, a hexagon-shaped pattern, a network pattern, or a double cross shaped pattern. The method can further include the steps of generating many nucleuses by using the electrode pattern or the mask pattern composed of the aggregates of micropatterns, forming another electrode pattern or another mask pattern corresponding to the desired region, and then applying a given voltage into the desired region to generate a ferroelectric spontaneous polarization reversal around the nucleuses.

Method for forming polarization reversal

It is an object to provide an optical control device capable of realizing speed matching between a microwave and a light wave or impedance matching of microwaves and of reducing a driving voltage. An optical control device including a thin plate() which has an electro-optical effect and has a thickness of 10 &#x3bc;m or less, an optical waveguideformed in the thin plate, and control electrodes for controlling light passing through the optical waveguide is characterized in that the control electrodes are configured to include a first electrode and a second electrode disposed to interpose the thin plate therebetween, the first electrode has a coplanar type electrode including at least a signal electrodeand a ground electrode, and the second electrode has at least a ground electrode() and is configured to apply an electric field to the optical waveguide in cooperation with the signal electrode of the first electrode.

Optical control device

A method for forming a ferroelectric spontaneous polarization reversal, including the steps of forming a concave portion on a top face of a ferroelectric substrate or a bottom face of a ferroelectric substrate, and applying an electric field into the substrate, wherein a ferroelectric spontaneous polarization reversal is formed at least in one portion of a region of the substrate with the concave portion, and wherein the shape of the concave portion is configured such that the width of the concave portion gets narrower gradually toward the inside of the substrate. The method may further include the steps of, after the reversal, making into almost a flat-plane the top or bottom face having the concave portion, and then, forming a new concave portion in another region and applying an electric field to form another reversal in one portion of the region of the substrate having the new concave portion.

A method for forming a ferroelectric spontaneous polarization reversal includes the steps of forming a convexo-concave structure on a top face of a ferroelectric substrate firstly, and then forming a ferroelectric spontaneous polarization region on the substrate including one portion of a convex portion, with a concave portion being formed on the bottom face of the substrate within a region where a ferroelectric spontaneous polarization reversal is to be formed and the convex portion is formed, and then applying an electric field into the substrate. The depth of the concave portion on the bottom face of the substrate may be greater than the height of the convex portion on the top face of the substrate. The width of the concave portion on the bottom face of the substrate may be wider than width of said convex portion on the top face of the substrate.

A method for forming a ferroelectric spontaneous polarization reversal in a desired region of a ferroelectric substrate, wherein thickness of the ferroelectric substrate in the desired region A of the ferroelectric substrate is thinner than in a region B outside the desired region of the substrate, comprising the step of applying a given voltage into the ferroelectric substrate by a liquid electrode method to thereby form a ferroelectric spontaneous polarization reversal in the desired region of the ferroelectric substrate.

Method for forming ferroelectric spontaneous polarization reversal

An optical device and a method of manufacturing the optical device, with the method including the steps of forming a dopant layer on a stoichiometric lithium niobate single crystal substrate with Li to Nb mole composition ratio of 49.5% to 50.5%, and diffusing a dopant in the dopant layer into at least a portion of the stoichiometric lithium niobate single crystal substrate. The stoichiometric lithium niobate single crystal substrate includes 0.5 to 5 mol % of Mg. In the diffusing step, a heat treatment is performed at a diffusion temperature of 1000&#xb0; C. to 1200&#xb0; C. for a diffusion time of 3 hours to 24 hours in a dry atmosphere of at least one of O, N, Ar and He gas having a dew-point temperature of &#x2212;35&#xb0; C. or less.

Optical device and method of manufacturing the same

The purpose of present inventions is to provide an optical control device having a single-mode waveguide in the optical control device having the ridge waveguide, and to stably manufacture and provide the optical control device having the single-mode waveguide with high precision even when the substrate is a thin plate with the thickness of 10 &#x3bc;m or less. An optical control device having a substrateformed with an optical waveguide, in which the substrate is a thin plate with a thickness of 10 &#x3bc;m or less, at least a portion of the optical waveguide is configured as a ridge waveguide, a trenchhaving a width of 10 &#x3bc;m or less is formed on both sides of at least portions of the ridge waveguide, and a taper waveguide section (area B) continuously changes a light propagation mode of the waveguide between a single-mode and a multi-mode by continuously changing the width or depth of the trench. Additionally, it is desirable that the taper waveguide section is disposed at least in one of a light input section and a light output section, and light propagating through the waveguide is in the single-mode in a section in which the taper waveguide section is disposed.

Optical control device and manufacturing method thereof

A nested modulator is provided where the circuit arrangement of modifying electrodes including signal electrodes is simplified, and at the same time, the drive voltage can be lowered. A nested modulator, including: a substratemade of a material having electro-optic effects; an optical waveguide formed on the substrate; and a modulating electrode for modulating light waves which are guided through the optical waveguide, wherein the optical waveguide has a main Mach-Zehnder waveguideand sub-Mach-Zehnder waveguidesandprovided on two branching waveguides of the main Mach-Zehnder waveguide, and the modulating electrode is provided in a sub-branching waveguide of the sub-Mach-Zehnder waveguides, is characterized in that a polarization reversal regionoris formed in a portion of a sub-branching waveguide of each of the sub-Mach-Zehnder waveguides, the modulating electrode is formed of signal electrodes including introduced signal electrodesor, branching single electrodesorand lead signal electrodesoras well as ground electrodes for each of sub-Mach-Zehnder waveguides, and the branching signal electrodes which branch from the introduced signal electrode are placed so as to work on two sub-branching waveguides for each of the sub-Mach-Zehnder waveguides.

Nested modulator

The present invention provides a highly-integrated and compact optical element and further provides an optical element having various functions such as lower driving voltage, chirping suppression and polarization-independency. The optical element comprising a substrateconsisting of a material having an electrooptic effect, top optical waveguides-an-formed on the top face of said substrate, bottom optical waveguides formed on the bottom face of said substrate, a top modulating electrode for controlling the phase of a light wave being propagated through said top optical waveguide, and a bottom modulating electrode for controlling the phase of a light wave being propagated through said bottom optical waveguide, is characterized in that at least one side edge of said substrate comprises output and input of said optical waveguides formed on said top and bottom faces, and a turnback element is located adjacent to said one side edge to guide the light wave from said output to said input.

Optical device

The present invention intends to control DC drift phenomenon in a light control element having ridge structure, and to provide a light control element with high drive stability in a large area. The present invention has character that, in a light control element being equipped with a base plate that has an electrooptic effect, an optical guide and an electrode for modulation that are formed on said base plate, which has ridge structure, an anti-DC drift layer is installed on the surface of the above mentioned base plate where the optical guide is formed, and annealing treatment is performed after ridge processing.

Light control element

There is provided a high performance optical waveguide type optical modulator with excellent long term reliability, in which contamination of the buffer layer in a forming process of a signal field adjustment region on the buffer layer by a lift-off method or an etching method, is prevented and DC drift thus suppressed. The optical waveguide type optical modulatorcomprises a substratehaving an electro-optic effect, optical waveguidesformed on the surface of this substratea traveling-wave type signal electrodeand ground electrodeswhich are provided on the substrateand control a lightwave, and a buffer layerprovided between the electrodesand the optical waveguidesand furthermore, a dielectric layeris provided on the entire surface of the buffer layeron the side of the electrodesand a signal field adjustment regionwhich has a wider width than that of the traveling-wave type signal electrodeand is made of a material with a higher refractive index than that of the dielectric layeris formed between the dielectric layerand the traveling-wave type signal electrode

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Tokyo, Japan

Futoshi Yamamoto