Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Olympus Corporation

Toray Industries, Inc.

Ryoichi Kasahara

Takahiro Kashiwazaki

Osamu Tadanaga

Takushi Kazama

Takeshi Umeki

Koji Embutsu

Nobutatsu Koshobu

Ikuo Ogawa

Asuka Inoue

Satomi Katayose

Yusuke Nasu

Toshiki Nishizawa

Yuji Mitsuhashi

Katsuhiko Hirabayashi

Kenya Suzuki

Takashi Saida

Nobuaki Matsuura

Takayuki Ogasawara

Kei Kuwabara

Yuji Fujiwara

Takayuki Mizuno

Kei Watanabe

Fumihiro Ebisawa

Daichi Watanabe

Yu Kurata

Yasuhiro Sato

Masanobu Sato

Yuichi Suzuki

Atsushi Aratake

Takashi Goh

Michiko Seyama

Shunichi Soma

Ai Yanagihara

Junji Sakamoto

Takako Ishihara

Mikitaka Itoh

Koji Fujii

Kazunori Seno

Yasuhiro Hida

Yuko Kawajiri

Takuro Tajima

Emiko Ishikawa

Keiji Takeda

Kazuhiko Takagahara

Ryusuke Kawano

Noriko Nagai

Atsushi Horiuchi

Hisanobu Tanigawa

Takurou Tajima

Ryosuke Saito

Nobutatsu Koshoubu

A planar optical waveguide device which has improved resistance to optical loss and improved stability of the entire system of balanced homodyne detection is realized. An embodiment is an optical waveguide device for measurement of squeezed light using balanced homodyne detection, including an amplifier circuit that is connected to a signal light input port for inputting the squeezed light and performs phase-sensitive amplification, and a multiplexing/demultiplexing circuit that is connected to a local oscillator optical input port and an output of the amplifier circuit, has local oscillator light and the amplified squeezed light incident on the circuit, and outputs the light interfering with each other to two output ports.

Planar optical waveguide device for measuring amplitude phase of squeezed light

Even when excitation light having large power is used, damage at the end face of the optical fiber is suppressed, and reduction in wavelength conversion efficiency and reduction in phase sensitive amplification gain are prevented. An embodiment of the present invention relates to a wavelength conversion apparatus for performing a wavelength conversion operation by inputting a fundamental wave and a second-order harmonic into a second-order nonlinear optical medium, the wavelength conversion apparatus comprising: a second-order harmonic input optical fiber optically coupled to a waveguide of the second-order nonlinear optical medium, for inputting the second-order harmonic into the waveguide; and a second-order harmonic output optical fiber optically coupled to a waveguide, for outputting the second-order harmonic output from the waveguide, wherein the second-order harmonic input optical fiber and the second-order harmonic output optical fiber are polarization maintaining fibers.

Wavelength conversion apparatus

An optical amplifier of the present disclosure includes a Raman amplification unit and a parametric amplification unit that is configured of a second-order nonlinear element including a PPLN waveguide. In the optical amplifier, second harmonic lights are generated from a fundamental wave light having a wavelength that is slightly detuned to a shorter wavelength side with respect to a phase matching wavelength of the second-order nonlinear element, and is utilized as excitation light for the parametric amplification unit. By utilizing the excitation light based on the fundamental wave light of the wavelength detuned from the phase matching wavelength, a phase matching curve can be obtained in a wide band in a difference frequency generation (DFG) process of the second-order nonlinear element. The reduction in conversion efficiency of the wavelength near the excitation light in the parametric amplification unit is compensated by the Raman amplification unit.

Optical amplifier

To manufacture an optical waveguide including a substrate, a lower cladding layer formed on the substrate, a core layer formed on the lower cladding layer, a sinking prevention layer formed to cover the core layer and the lower cladding layer, and an upper cladding layer formed on the sinking prevention layer, in which the sinking prevention layer is composed of a material having a higher melting point than that of a material composing the lower cladding layer.

Optical waveguide and manufacturing method thereof

In a wavelength conversion apparatus, reflection suppressors are provided on surfaces of optical elements indicating lenses, dichroic mirrors, and sealing windows excluding a wavelength conversion element in the apparatus between optical fibers Fand Fon the input side and optical fibers Fand Fon the output side, and on end surfaces of the optical fibers Fand Fon the output side. With this, even when light having a wavelength of a sum frequency component of signal light and excitation light is generated at the operation time of wavelength conversion of the wavelength conversion element, because the reflection suppressors suppress the reflection of unwanted light of the wavelength band, the unwanted light is unlikely to return to the wavelength conversion element and it is also possible to suppress a situation in which the unwanted light is mixed into the optical fibers Fand F

A wavelength conversion element manufacturing method capable of realizing, in a wavelength conversion element having a structure in which a thin film substrate having a periodic polarization inversion structure and a support substrate are laminated, highly efficient wavelength conversion by confining light in a cross-sectional area smaller than in the known art. The manufacturing method includes steps of forming a periodic polarization inversion structure on a first substrate made of a second-order nonlinear optical crystal and forming a damage layer in the first substrate by implanting ions from one substrate surface to obtain a first substrate for bonding, directly bonding a second substrate having a bonding surface having a smaller refractive index than the first substrate to the one substrate surface of the first substrate at the bonding surface, and peeling the first substrate directly bonded to the second substrate being the support substrate with the damage layer as a boundary to remove a part of the first substrate.

Wavelength conversion element and method for producing same

An end portion structure of a transmission line of the present invention is a structure in which a protective film with a thickness of 0.5 μm to 3.0 μm is formed on the end surface of the transmission line in place of an end cap formed in an end portion of a transmission line in the related art, and no adhesive is used in a portion through which light passes. The protective film on the end surface works to suppress a bulge of the core. The thickness of the protective film is significantly thinner than the end cap, and thus waveguides facing each other can be brought close to each other. It is possible to reduce the connection loss between two fibers or waveguides facing each other to be 0.5 dB or less. Since no adhesive is used, there is no loss increase caused by adhesive deterioration.

End structure of a waveguide

Reduction of output power of light with a wavelength converted is suppressed, which is caused by a pyroelectric effect that occurs when a temperature of a wavelength conversion element including a ferroelectric substrate is changed. Provided is a wavelength conversion device that generates light different from a wavelength of a signal light when the signal light is inputted, and includes a wavelength conversion element that converts a wavelength of the signal light, and a temperature control element for controlling a temperature of the wavelength conversion element, wherein the wavelength conversion element and the temperature control element are sealed in an inside of a metal casing, the inside of the metal casing is filled with dry gas including one kind or more selected from nitrogen, oxygen, argon or helium, the wavelength conversion element includes an optical waveguide core and a substrate having a lower refractive index to the signal light than the optical waveguide core, and the substrate is a ferroelectric substance in which directions of spontaneous polarization are random.

Wavelength conversion device

A method for adjusting a transmission wavelength of signal light transmitted through an optical waveguide device provided with one or more optical waveguides through which the signal light having a wavelength of 1520 nm to 1560 nm and blue light having a wavelength of 375 nm to 455 nm pass, a groove through which the waveguide passes, and resin filled in the groove, including a step of passing the signal light and the blue light through the same or mutually different one or more optical waveguides and of passing the signal light and the blue light through the same or mutually different resin, the latter step changing a refractive index of the resin by irradiating the resin with the blue light so as to change the transmission wavelength of the signal light transmitted through the resin in accordance with a change in the refractive index of the resin.

Method for adjusting transmitted wavelength of signal light transmitted through optical waveguide device

With a wavelength conversion device based on a nonlinear optical effect, when arrayed waveguides including an intended nonlinear waveguide are fabricated, unwanted slab waveguides are inevitably formed. The slab waveguides can cause an erroneous measurement in the selection of a waveguide having desired characteristics from the arrayed waveguides. The erroneous measurement can lead to redoing steps for fabricating the wavelength conversion device and a decrease in the yield and inhibit the evaluation of the characteristics in selection of the waveguide and the subsequent fabrication of the wavelength conversion device from being efficiently performed. A wavelength conversion device according to the present invention includes a plurality of waveguides formed on a substrate, and a plurality of slab waveguides that are arranged substantially in parallel with and spaced apart from the plurality of waveguides, and each of the slab waveguides has a grating structure that reflects light of a particular wavelength.

Wavelength conversion element and method for manufacturing same

According to the present disclosure, it is possible to realize an optical communication system in which a relay-type PSA and homodyne detection are efficiently combined using a single phase synchronization mechanism. Intensity noise and phase noise can be suppressed to a very low level, and accurate transmission of signals with increased multiplicity is enabled. By utilizing the features of the PSA to extract the phase of a single carrier using the sum frequency light of the signal light and its phase-conjugated light, the number of pilot carriers can be reduced compared to the configuration of the conventional optical communication system, and it is possible to suppress unnecessary nonlinear noise.

Optical communication system

A highly-efficient ridge waveguide includes a base substrate of a single-crystal and a core substrate made of a nonlinear optical medium, the base substrate and the core substrate being directly bonded, and includes a thin film layer formed on a surface of the core substrate on the upper side of a periodically polarization-reversed structure, and becomes a wavelength conversion element. A direct bonding method through thermal diffusion is applied to bonding. The core substrate has a ridge structure formed in a light propagating direction and a reversed structure formed by processing this. A surface of the core substrate is ground and a thin film layer is formed on the ground surface. A core formed by digging a core layer of the core substrate in an unbonded state is provided on an upper surface of an undercladding layer of the base substrate in a bonded state. Two side surfaces of the core are in contact with an air layer.

Optical element and manufacturing method thereof

Provided is an optical waveguide circuit in which the space between waveguides, a waveguide groove, or the space between fibers is filled with a resin where a wavelength shifts to positive (shifts backward) instead of a conventional resin where a wavelength shifts to negative (shifts forward), to return a refractive index having decreased by an instantaneous change to the original refractive index. In the filling resin with which the space between the waveguides, the waveguide groove, the space between the fibers, or the space between the fiber and the waveguide is filled, upon input of light, a refractive index of a portion through which the light passes instantaneously decreases, and then the refractive index gradually increases to compensate the initial decrease in the refractive index.

Filling resin and optical waveguide circuit filled with filling resin

A wavelength conversion optical element using a nonlinear optical effect of a device structure in which wavelength conversion efficiency rises as targeted when the length of a waveguide is increased is provided. The element adopts a waveguide structure using lithium niobate of a second-order nonlinear optical material. Wavelength conversion regions are formed to correspond to two linear waveguides extending in parallel to each other on a plane of the planar structure and correspond to the lengths of the two linear waveguides. One end side of the linear waveguide is an incident side of excitation light and one end side of the linear waveguide is an emission side of wavelength converted light. The linear waveguides excluding the incident side and the emission side are joined by a bent waveguide. Second-order nonlinear optical media forming the linear waveguides have polarization inversion structures in which directions of spontaneous polarization are periodically inverted with respect to a propagation direction of light.

Wavelength conversion optical element

A wavelength conversion device includes a second-order nonlinear optical medium with a polarization inversion structure, wherein the wavelength conversion device performs wavelength conversion between three wavelengths according to a relationship of 1/&#x3bb;=1/&#x3bb;+1/&#x3bb;, a polarization inversion period &#x39b; of the polarization inversion structure is divided into 2a regions, and when the 2a regions divided from the polarization inversion period &#x39b; each has a width ratio of an inverted region and a non-inverted region of r to 1&#x2212;r (where 0&#x2264;r&#x2264;1), a ratio value r is set such that, when one period in phase of a sine function from 0 to 2&#x3c0; is divided into 2a regions, a value of the sine function in a center of each divided region is (1&#x2212;2r)&#xb1;0.1.

Growing community of inventors

Atsugi, Japan

Ryoichi Kasahara