Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Tohoku University

Mikitaka Itoh

Yasuyuki Inoue

Yasuhiro Hida

Masahiro Yanagisawa

Takashi Saida

Tsutomu Kitoh

Hiroshi Terui

Mitsuru Nagano

Tomoyo Shibazaki

Takanori Ishikawa

Takayuki Mizuno

Shin Kamei

Akio Sugita

Hiroyuki Ishii

Naoki Fujiwara

Hiroshi Takahashi

Kei Watanabe

Ryoichi Kasahara

Takuya Tanaka

Takashi Goh

Kiyofumi Kikuchi

Hirotaka Nakamura

Masataka Nakazawa

Shinya Tamaki

Shunji Kimura

Akimasa Kaneko

Tomohiro Shibata

Yoshinori Hibino

Toshimi Kominato

Masaki Kohtoku

Keisuke Kasai

A configuration of a DFB laser-based wavelength tunable laser is well known, but long resonators have difficulty in forming uniform resonators due to production variations, thereby inducing limitation in narrowing the spectral linewidth in the DFB laser-based wavelength tunable laser as well. In the semiconductor laser device of the present invention, a semiconductor laser that oscillates in a single mode and a low-loss lightwave circuit using SiOglass are arranged on the common substrate. The lightwave circuit is configured such that part of output light from the semiconductor laser propagates through a certain length of an optical path, and then is reflected by a reflector and is fed back to the semiconductor laser. Output light from the semiconductor laser and an input waveguide of the lightwave circuit can also be configured to be optically connected directly to each other. The present invention can provide a compact laser device with a narrowed spectral linewidth and stable wavelength controllability.

Semiconductor laser device

In a waveguide device, unnecessary optical power is appropriately terminated. According to an embodiment of the present invention, the waveguide device has a termination structure filled with a light blocking material to terminate light from a waveguide end. In the termination structure, a cladding and a core are removed to form a groove on an optical waveguide. The groove is filled with a material (light blocking material) that attenuates the intensity of light. Thus, light input to the termination structure is attenuated by the light blocking material, suppressing crosstalk which possibly effects on other optical devices. Thus, such a termination structure can restrain crosstalk occurred in optical devices integrated in the same substrate and can also suppress crosstalk which possibly effects on any other optical device connected directly to the substrate.

Optical waveguide device and module

A multi-stage interferometer circuit of the present invention includes: a multiplexing port; (N&#x2212;1) stages of lattice type two-beam interferometers, wherein each stage includes a two-beam delay circuit having a path length difference of an integral multiple of M&#xb7;&#x394; L/2, and wherein the two-beam delay circuit of the lattice type two-beam interferometer of the first stage is connected to the multiplexing port; an M-beam interferometer including: two sets of 1&#xd7;(M/2) optical couplers connected to the first optical coupler of the lattice type two-beam interferometer at the final stage; an M-array delay circuit, each delay circuit of which has a delay length different from each other by &#x394;L; and M&#xd7;M optical couplers; and M demultiplexing ports, wherein one or more transversal filters are arranged inside the multi-stage interferometer circuit so that the light guided between the demultiplexing port and the multiplexing ports passes therethrough at least once.

Multi-stage interferometer circuit with waveform shaping function

An arrayed waveguide grating provided with a first slab waveguide formed on a substrate; a second slab waveguide formed on the substrate; a first input/output waveguide connected to the first slab waveguide; a second input/output waveguide connected to the second slab waveguide; two or more channel waveguide groups connecting the first and second slab waveguides, each of the channel waveguide groups formed of an aggregate of a plurality of channel waveguides having path lengths sequentially becoming longer by a predetermined path length difference; and an optical filter arranged in at least one of the first and second slab waveguides.

Arrayed waveguide grating, optical module provided with said arrayed waveguide grating, and optical communications system

An optical wavelength multi/demultiplexing circuit is provided in which temperature dependence at a transmission center wavelength remained in an athermalized AWG is compensated. An AWG according to an embodiment of the present invention is compensated for the main temperature dependence at the transmission center wavelength. The AWG comprises an optical splitter, a first and second arm waveguides, an optical mode combining coupler and a multimode waveguide between an input/output waveguide and a slab waveguide. The optical mode combining coupler couples fundamental mode light from the first arm waveguide as fundamental mode and the fundamental mode light from the second arm waveguide as first mode. The multimode waveguide is capable of propagating the fundamental and first mode light. This AWG is configured such that the temperature dependence remained in the arrayed waveguide grating is compensated by changing the optical path length difference between the first and second arm waveguides with temperature.

Arrayed waveguide grating

An optical wavelength multiplexing/de-multiplexing circuit having a low loss and a flat transmission spectrum is provided. The optical wavelength multiplexing/de-multiplexing circuit compensates a temperature dependence of a center transmission wavelength which remains in an athermal AWG, and has an excellent accuracy of the center transmission wavelength in a whole operating temperature range or has a comparatively wide operable temperature range. The temperature dependence of the transmission wavelength in the athermal MZI is modulated and set so as to cancel the temperature dependence of the center wavelength which remains in the athermal AWG. The present invention focuses particularly on an optical coupler in the MZI and modulates the temperature dependence of the transmission wavelength in the MZI by providing the optical coupler itself with a mechanism which changes a phase difference between two outputs by temperature.

Optical wavelength multiplexing/ de-multiplexing circuit

A planar lightwave circuit is provided. The planar lightwave circuit includes a waveguide and a spotsize converter which is a part of the waveguide, wherein a core is embedded in a cladding in the waveguide, and the spotsize converter is located near an end face of a substrate on which the planar lightwave circuit is formed, the spotsize converter including: a core width fine-tuning part in an end face side of the substrate; and a core width converting part which follows the core width fine-tuning part; wherein core width of the spotsize converter is minimum at an end face of the substrate, a mean taper angle &#x3b8;of the core width fine-tuning part is larger than 0&#xb0; and smaller than a mean taper angle &#x3b8;of the core width converting part.

Planar lightwave circuit and optical circuit

A silica-based optical waveguide circuit serves to reduce the time required to production while allowing a spot size converting function to work sufficiently. In a silica-based optical waveguide circuit comprising an input/output waveguide core formed to be thicker than an waveguide core and a tapered portion for connecting the input/output waveguide core and the waveguide core, wherein the waveguide circuit further has a core layer at each side of the input/output waveguide core, a thickness T of the core layer at the side of the input/output waveguide core is smaller than the thickness H of the input/output waveguide core.

Silica-based optical waveguide circuit and fabrication method thereof

An optical waveguide and an optical waveguide circuit having polarization insensitivity or a required low-level polarization dependence without degradation of the optical characteristics and reliability are disclosed, and a fabricating method of an optical waveguide and an optical waveguide circuit having polarization insensitivity or a required low-level polarization dependence without increasing the fabricating burden and the cost are disclosed. The optical waveguide comprises a planar substrate; a lower cladding which is provided on the planar substrate, where the lower cladding has a ridge; a core, provided on the ridge of the lower cladding, for transmitting light; and an upper cladding provided in a manner such that the core is covered with the upper cladding. The ridge has a shape predetermined so as to decrease polarization dependence of the optical waveguide to a required low level.

Optical waveguide and fabricating method thereof, and optical waveguide circuit

An optical waveguide circuit is provided that can reduce or eliminate polarization dependence by reducing or eliminating birefringence. A substrate consists of a silicon substrate, and a cladding and a core are composed of silica-based glass. The core has a multilayer structure composed of a few types of layers with different refractive indices such as first core layers and second core layers stacked in the direction parallel to the substrate. As for the birefringence of the waveguide, the geometrical birefringence caused by the multilayer structure is canceled out by the other birefringence, thereby being able to reduce or eliminate the birefringence of the waveguide.

Optical waveguide circuit

This planar lightwave circuit includes a buried layer formed in a region between at least two cores branching from a branching point to decrease in thickness as the spacing between the cores increases with an increase in distance from the branching point. The planar lightwave circuit is designed to suppress scattering of light signals at the branching point.

Planar lightwave circuit

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Atsugi, Japan

Mikitaka Itoh