Nippon Telegraph and Telephone Corporation

Masahiro Sasaura

Tadayuki Imai

Kazuo Fujiura

Seiji Toyoda

Takashi Kurihara

Koji Enbutsu

Shogo Yagi

Makoto Shimokozono

Akiyuki Tate

Makoto Abe

Eishi Kubota

Touru Matsuura

Hiroshi Fushimi

Tohru Matsuura

Jun Miyazu

Hiroki Kohda

Takashi Kobayashi

Kazuhito Higuchi

Mitsuru Shinagawa

Tadashi Minotani

Noboru Sonehara

Tsutomu Horikoshi

Takaaki Akimoto

Kouichirou Nakamura

Nobutarou Shibata

Haruhiko Kojima

Aiichirou Sasaki

Highly-qualified crystals are grown with good yield under an optimal temperature condition by controlling the axial temperature distribution in the vicinity of the seed crystal locally. In an apparatus for producing crystals to grow crystals wherein a seed crystalis placed in a cruciblewhich is retained in a furnace, raw materialsfilled in the crucibleare heated and liquefied, and a raw materialslowly cooled in the cruciblefrom below upward, the apparatus including a temperature controller for controlling temperature to cool or heat the vicinity of the seed crystallocally. The temperature controller controls the temperature by a hollow constructed capmounted outside the portion of crucibleand regulates refrigerant flow running through the hollow portion.

Apparatus for producing crystals

A variable focusing lens is provided that can change the focal length at a high speed. The variable focusing lens includes: a single crystal electrooptic material having inversion symmetry; a first anode formed on a first surface of the electrooptic material; a second cathode provided to have an interval to the first anode; and a first cathode and a second anode that are formed on a second surface opposed to the first surface and that are formed at positions opposed to the first anode and the second cathode. An optical axis is set so that, when light enters through a third face orthogonal to the first surface, light exists through a fourth surface opposed to the third face. A voltage applied between the first and the second pair of electrodes is changed to thereby change the focal point of light emitted from the fourth surface of the electrooptic material.

Variable focusing lens and microscope

To provide a variable-focal length lens capable of altering its focal length at high speed. The variable-focal length lens has an electrooptic material and electrodes formed on an incident surface of light and on an exit surface of the light of the electrooptic material. An optical axis is set so that the light is inputted into a gap where the electrodes of the incident surface are not formed and is outputted from a gap where the electrodes of the exit surface are not formed. A focus of the light that is transmitted through the electrooptic material becomes variable by varying an applied voltage between the electrodes of the incident surface and the electrodes of the exit surface.

Variable-focal length lens

The present invention relates to an electric field sensor including: a light source (); an electro optic crystal () which is applied with an electric field based on a signal under test, in which a birefringent index changes according to the electric field, and which changes a polarization state of light incident from the light source according to the birefringent index and emits the light; and a detector () that detects an electric signal according to the change of the polarization state of the light emitted from the electro optic crystal (). Further, the electric field sensor includes: a signal electrode () for applying the electric field based on the signal under test to the electro optic crystal (); a counter electrode () that forms a pair with the signal electrode (); and an auxiliary electrode () that is electrically connected to the counter electrode (), and that forms a capacitance with ground.

Electric field sensor

An optical medium having a high refractive index without anisotropy and a wide transmission wavelength is obtained. The cubic crystal material is &#x3b1;&#x3b2;O, where &#x3b1; is at least one of K, Ba, Sr, Ca, and &#x3b2; is at least one of Ta, Ti. Optimally, the cubic crystal material is KTaNbO, where composition x is 0&#x2266;x&#x2266;0.35. This composition enables to raise refractive index while its phase transition temperature is below a room temperature.

Optical medium, an optical lens and a prism

A method and an apparatus for producing crystals wherein crystal quality can be kept and a crystal composition is uniformed from a growth early stage to a growth last stage are provided. In an apparatus for producing crystals wherein the crystalsare grown from a liquefying raw materialin a crucible retained in a furnace and slowly cooling the raw materialin the cruciblefrom below upward, the apparatus comprises a raw material supply apparatuswhich supplies a resupply raw material, and a reflection plateplaced above the crucible, which liquefies the resupply raw materialsupplied from the raw material supply apparatusand drops it as a liquid into the crucible.

Method and apparatus for producing crystals

The present invention provides an optical switch, an optical modulator, and a wavelength variable filter each of which has a simple configuration, which requires only a low driving voltage, which is independent of polarization, and which can operate at high speed. An optical switch according to the present invention includes a 3-dB coupler () placed on an input, a 3-dB coupler () placed on an output, and two optical waveguides connecting the input-side 3-dB coupler and the output-side 3-dB coupler together. The optical switch also includes a phase modulating section () that applies electric fields to one or both of the two optical waveguides. At least two optical waveguides are a crystal material including KTaNbO(0&#x3c;x&#x3c;1) and KLiTaNbO(0&#x3c;x&#x3c;1, 0&#x3c;y&#x3c;1), or KTaNbOor KLiTaNbO.

Optical switch, optical modulator and wavelength variable filter

An optical switch, an optical modulator, and a wavelength variable filter each have a simple configuration, which requires only a low driving voltage, which is independent of polarization, and which can operate at high speed. An optical switch includes a 3-dB coupler placed on an output, a 3-dB coupler placed on an output, and two optical waveguides connecting the input-side 3-dB coupler and the output-side 3-dB coupler together. The optical switch also includes a phase modulating section that applies electric fields to one or both of the two optical waveguides. At least two optical waveguides are a crystal material including KTaNbO(0&#x3c;x&#x3c;1) and KLiTaNbO(0&#x3c;x&#x3c;1, 0&#x3c;y&#x3c;1), or KTaNbOor KLiTaNbO.

The invention provides an optical waveguide material whose refractive index can be tailored without changing the ratio of Ta and Nb. An optical waveguide of this invention comprising an under-clad layerand a corethat is formed on the under-clad layerand has a higher refractive index than that of the under-clad layeris shown. For example, KTN (KTaNbO) is used as the core, and a material that is obtained by substituting at least one element selected from the group consisting of Zr, Hf, and Sn for a portion of one element of the constituent elements of KTN and has the same perovskite type crystal structure as KTN is used as the clad. The refractive index of KTN can be reduced considerably, and this controllability widens the degree of freedom in the design of optical waveguide devices.

Optical waveguide material and optical waveguide

An optical waveguide capable of having various characteristics and a method of manufacture thereof as well as a method of manufacturing a crystal film are provided. An optical functional material KTaNbOis used as an optical waveguide. The input optical signal is transmitted to the KTaNbOfilm. The KTaNbOfilm undergoes changes in optical property when an external voltage signal is applied to the electrode. Therefore, as it passes through the KTaNbOfilm, the input optical signal is modulated by the characteristic change. The modulated optical signal is taken out as an output optical signal.

Optical waveguide and method of manufacture

A wavelength converter implements high speed, high efficiency, low noise wavelength conversion without performing high voltage poling of a crystal, and enables switching and modulation of converted light in response to an electric field. A KLTN crystal, includes a deposited-gold electrode within its incidence plane, and is connected to a DC power supply via a copper wire. The crystal material is composed of KTa Nb O and/or K Li Ta Nb O . A polarizer controls the polarization of the fundamental wave in the direction parallel to the electric field, and launches it into the electrode of the KLTN crystal. The KLTN crystal, rotating on an axis in the direction of the electric field, launches only part of the generated SHG light with the same polarization direction as that of the incident light into a photo multiplier tube through a polarizer.

Growing community of inventors

Atsugi, Japan

Masahiro Sasaura