Nippon Telegraph and Telephone Corporation

Shinji Matsuo

Hiroyuki Suzuki

Takaaki Kakitsuka

Koji Takeda

Hidetaka Nishi

Tai Tsuchizawa

Tatsuro Hiraki

Ryo Nakao

Tatsurou Hiraki

Toshikazu Hashimoto

Yusuke Muranaka

Takashi Kurokawa

Nobuhiro Nunoya

Takuma Aihara

Nikolaos-Panteleimon Diamantopoulos

Erina Kanno

Takeshi Yamada

Hideaki Matsuzaki

Masahiro Nada

Akihiko Shinya

Masaya Notomi

Chikara Amano

Kenji Kurishima

Toru Segawa

Seiji Fukushima

Takashi Kozawaguchi

Hideki Hukano

Suguru Yamaoka

An embodiment plasmonic waveguide includes a first metal layer formed on a substrate, an electro-optic thin film formed on the first metal layer and including a material having an electro-optic effect, and a second metal layer formed on the electro-optic thin film. In an embodiment, a waveguide region in which the first metal layer and the second metal layer overlap each other in a direction normal to a planar surface of the substrate (layer stacking direction), the waveguide region extending in the planar surface direction of the substrate, is included. For example, the first metal layer and the second metal layer are formed only in the waveguide region, and each of respective widths of the first metal layer and the second metal layer is equal to a width of an overlap between the first metal layer and the second metal layer.

Plasmonic waveguide

A wavelength tunable laser includes a filter region having a wavelength selection function on light from a gain region, wherein the filter region is a Sagnac interferometer and includes two ring resonators. The ring resonator has two optical couplers, and first and second curved waveguides connecting the two optical couplers, each of the two optical couplers is configured to receive input of the light from the gain region through an input-output port, to couple light of a resonant peak to a bar port of the input-output port, and to couple light except light at a resonant peak wavelength to a cross port of the input-output port, and the first curved waveguide connects the bar ports of the input-output ports of the two optical couplers, and the second curved waveguide connects the cross ports of ports, of two optical couplers, that the first curved waveguide is connected to.

Tunable laser

A wavelength tunable laser includes a filter region having a wavelength selection function on light from a gain region, wherein the filter region is a Sagnac interferometer and includes two ring resonators. The ring resonator has two optical couplers, and first and second curved waveguides connecting the two optical couplers, each of the two optical couplers is configured to receive input of the light from the gain region through an input-output port, to couple light of a resonant peak to a bar port of the input-output port, and to couple light except light at a resonant peak wavelength to a cross port of the input-output port, and each of radiation waveguides connected to the cross ports of the input-output ports of the two optical couplers has a structure that radiates the light except the light at the resonant peak wavelength to a front surface or a back surface of a substrate.

A device includes a first cladding layer, a waveguide laser, an absorption layer, and a second cladding layer. The absorption layer is constituted by an oversaturation absorption body such as graphene. Also, the absorption layer is provided between the active layer and the distributed Bragg reflection portion. The absorption layer is formed below a core forming an optical waveguide between the active layer and a distributed Bragg reflection portion.

Optical device

A semiconductor laser includes an active region, a first distributed-Bragg-reflector region disposed contiguously with the active region, and a second distributed-Bragg-reflector region. The first distributed-Bragg-reflector region is formed contiguously with one side of the active region in a waveguide direction and includes a first diffraction grating. The second distributed-Bragg-reflector region is formed contiguously with to the other side of the active region in the waveguide direction and includes a second diffraction grating. The first diffraction grating includes recessed portions formed through a diffraction grating layer formed in the first distributed-Bragg-reflector region and convex portions adjacent to the recessed portions. The diffraction grating layer is made of a dielectric material.

Semiconductor laser

A wavelength tunable laser formed on a substrate made of single-crystal silicon is provided. The wavelength tunable laser includes a light emitting portion made of a III-V compound semiconductor, and external resonators provided with an optical filter. Cores included in the external resonators are made of one of SiN, SiON, and SiO(n is smaller than 2).

Semiconductor optical element

A semiconductor laser includes a distributed feedback active region and two distribution Bragg reflecting mirror regions which are arranged to be continuous with the distributed feedback active region. The distributed feedback active region has an active layer which is composed of a compound semiconductor and a first diffraction grating. The first diffraction grating is composed of a recessed portion which is formed to extend through a diffraction grating layer formed on the active layer and a projection portion which is adjacent to the recessed portion.

A core, constituted by an amorphous undoped semiconductor (i type), which is formed on a lower clad layer, and a p-type layer and an n-type layer which are disposed on the lower clad layer with the core interposed therebetween and are formed in contact with the core are provided. The core is formed to be thicker than the p-type layer and the n-type layer. The p-type layer and the n-type layer are constituted by single crystal silicon.

Optical modulator

An optical device includes a core formed on a substrate, a first source electrode and a second source electrode formed in contact with both side surfaces of the core interposed between the first source electrode and the second source electrode, and a drain electrode formed in contact with an upper surface of the core. The core, the first source electrode, and the second source electrode together form a plasmonic waveguide. The first source electrode and the second source electrode are Schottky coupled to the core.

A core and a slab layer that are formed on a lower clad layer are provided. The lower clad layer is formed on a substrate. The core is comprised of a semiconductor and has a rectangular shape in a cross-sectional view. The slab layer is comprised of a semiconductor. The core and the slab layer have a thickness that allows only up to a secondary mode of light to be present. Further, the core and the slab layer are laminated on the lower clad layer. Further, the core and the slab layer are disposed to be optically coupled to each other.

Optical waveguide

A semiconductor optical module includes a semiconductor laser element region having an active layer, a first cladding layer which is formed such that the active layer is embedded therein, a second cladding layer which is formed underneath the active layer and the first cladding layer, and a heater unit which produces a temperature change in a waveguide; an optical waveguide element region including a spot-size converter which converts a spot size of incident laser light, and an optical waveguide core layer which is formed such that the spot-size converter is embedded therein, the first cladding layer contains InP, the second cladding layer is made of a material lower in refractive index and higher in thermal conductivity than the first cladding layer, and a third cladding layer which is made of a material lower in refractive index and lower in thermal conductivity than the second cladding layer is formed underneath the spot-size converter and the heater unit.

Semiconductor optical module

The optical modulator includes a lower cladding layer formed on a substrate, a core formed on the lower cladding layer, and an upper cladding layer formed on the core. The core is made of an InP-based semiconductor having a bandgap corresponding to a desired wavelength. Refractive indexes of the lower cladding layer and upper cladding layer are equal to or less than a refractive index of InP.

An embodiment semiconductor optical device includes an optical waveguide including a core, and an active layer extending in the waveguide direction of the optical waveguide for a predetermined distance and arranged in a state in which the active layer can be optically coupled to the core. The core and the active layer are arranged in contact with each other. The core is formed of a material with a refractive index of about 1.5 to 2.2, such as SiN, for example. In addition, the core is formed to a thickness at which a higher-order mode appears. The higher-order mode is an Emode, for example.

A semiconductor laser is provided with: an active layer that excites a transverse electric (TE) mode and a transverse magnetic (TM) mode of light and constitutes at least a part of a resonator guiding the TE mode and the TM mode of light; and a diffraction grating as a frequency difference setting structure that sets the difference in oscillation frequency between the TE mode and the TM mode of light higher than a relaxation-oscillation frequency.

A semiconductor layer formed on a clad layer and a light absorbing layer formed on the semiconductor layer are provided. The semiconductor layer includes a p-type region and an n-type region. The p-type region, which is of p-type, is provided on a side of one side portion of the light absorbing layer in a direction perpendicular to a direction in which light is guided, and the n-type region, which is of n-type, is provided on a side of another side portion of the light absorbing layer in the direction perpendicular to the direction in which light is guided. A p-type contact layer, which is of p-type, is formed on the p-type region, and an n-type contact layer is formed on the n-type region.

Growing community of inventors

Tokyo, Japan

Shinji Matsuo