Mitsubishi Denki Kabushiki Kaisha

Kyoto University

Mitsubishi Electric Corporation

Hitoshi Tada

Nobuaki Kaneno

Kazuhisa Takagi

Susumu Noda

Tadashi Kimura

Norio Hayafuji

Yasuaki Yoshida

Hirotaka Kizuki

Atsushi Sugitatsu

Harumi Nishiguchi

Tsutomu Yamaguchi

Takehiro Nishida

Tetsuo Shiba

Tomoko Kadowaki

Tatuya Kimura

Kenzo Mori

Yoshitatu Kawama

Yuji Okura

Kenichi Ono

Yasuo Nakajima

Yutaka Nagai

Tohru Takiguchi

Yasuhiro Kunitsugu

A back-surface-incidence semiconductor light element includes: a semiconductor substrate of a first conductivity type; a first semiconductor layer of a first conductivity type on the semiconductor substrate; a light absorbing layer on the first semiconductor layer; a second semiconductor layer on the light absorbing layer; and an impurity diffusion region of a second conductivity type in a portion of the second semiconductor layer. A region including a p-n junction between the first semiconductor layer and the impurity diffusion region, and extending through the light absorbing layer, is a light detecting portion that detects light incident on a back surface of the semiconductor substrate. A groove in the back surface of the semiconductor substrate surrounds the light detecting portion, as viewed in plan.

Semiconductor light detecting element with grooved substrate

A semiconductor laser is provided which emits laser light in which the intensity center of the far-field pattern in the horizontal direction does not vary with variation of the optical output and in which the shape of the far-field pattern in the horizontal direction is stable. The width of trenches is determined so that the magnitude (E) of the electric field at the center of a ridge and the magnitude (E) of the electric field at the edges of the trenches provide a ratio E/Ethat is larger than 0.0001 and smaller than 0.01. In a semiconductor laser with a double-channel ridge structure, layers having a larger equivalent refractive index than the trenches exist outside the trenches. Accordingly, the semiconductor absorbs the light distributed outside the trenches and it is possible to obtain laser light in which the intensity center of the far-field pattern in the horizontal direction does not vary with variation of the optical output and in which the shape of the far-field pattern in the horizontal direction is stable.

Semiconductor laser

A semiconductor laser is provided which emits laser light in which the intensity center of the far-field pattern in the horizontal direction does not vary with variation of the optical output and in which the shape of the far-field pattern in the horizontal direction is stable. The width of trenches is determined so that the magnitude (E) of the electric field at the center of a ridge and the magnitude (E) of the electric field at the edges of the trenches provide. a ratio E/Ethat is larger than 0.0001 and smaller than 0.01. In a semiconductor laser with a double-channel ridge structure, layers having a larger equivalent refractive index than the trenches exist outside the trenches. Accordingly, the semiconductor absorbs the light distributed outside the trenches and it is possible to obtain laser light in which the intensity center of the far-field pattern in the horizontal direction does not vary with variation of the optical output and in which the shape of the far-field pattern in the horizontal direction is stable.

A semiconductor device has a two-dimensional slab photonic crystal structure in which a substrate supports a sheet-like slab layer including, sequentially stacked, a lower cladding layer, an active layer, and an upper cladding layer. A periodic refractive index profile structure, in surfaces of the stacked layers, introduces a linear defect region that serves as a waveguide. A p-type region and an n-type region in the slab layer define a pn junction surface at a predetermined angle with respect to the surfaces of the stacked layers in the slab layer.

Method of manufacturing a semiconductor device including a slab layer with a periodic air hole structure and a linear defect region

Semiconductor device

A band discontinuity reduction layer having a band gap energy larger than that of that of an MQW (multiple quantum well) absorption layer and smaller than that of a p-InP clad layer is provided between the MQW absorption layer and the p-InP clad layer. In addition, a band discontinuity reduction layer having a band gap energy larger than that of the MQW absorption layer and smaller than that of an n-InP clad layer is provided between the MQW absorption layer and the n-InP clad layer. Consequently, as a pile-up of carriers is suppressed, a semiconductor light modulator with an enhanced response speed can be obtained.

Semiconductor light modulator

An optical waveguide ridge has a side with a flat portion extending uniformly from a top of the ridge to a surface of a semiconductor substrate, the flat portion being in contact with an exposed surface of the substrate. A p-type electrode extends from the top of the optical waveguide ridge downward in contact with a dielectric film on the flat portion of the optical waveguide ridge. The p-type electrode further extends over the dielectric film onto the exposed surface of the semiconductor substrate where an end of the electrode is a bonding pad.

Optical modulator and photonic semiconductor device

An integrated semiconductor laser-modulator device less affected by a fluctuating electric field due to modulating signals applied to the modulator has improved frequency characteristics. The integrated semiconductor laser-modulator includes an active layer, a beam waveguide layer having a bulk structure with a bandgap energy larger than that of the active layer but smaller than that of a laser beam absorption layer having a bulk structure, wherein waveguides of the laser and modulator are connected and aligned, and a cladding layer including a diffraction grating is disposed on top of or beneath the waveguides.

Method of manufacturing an integrated semiconductor laser-modulator device

A light modulator includes a semiconductor substrate having a main surface, a rear surface, and a grounding conductor on the rear surface. A wave guide section having a width is located on the semiconductor substrate. A bonding pad section on the semiconductor substrate is located adjacent to the wave guide section and an insulating layer covers the main surface of the semiconductor substrate. A portion of the insulating layer immediately opposite the bonding pad section includes a multiple layer structure of insulating films. An electrode opposite the bonding pad section is electrically connected to the wave guide section.

Light modulator

A light modulator having a reduced parasitic static capacitance includes a semiconductor substrate having a mesa section and a bonding pad section. A primary insulating film on the substrate continuously covers the mesa section and the bonding pad section. After a mask has been formed on a portion of the primary insulating film opposite the bonding pad section, the remaining portion of the primary insulating film is etched, followed by removal of the mask. After the removal of the mask, a second insulating film is formed continuously covering the primary insulating film opposite the bonding pad section and the mesa section so that a relatively thick insulating layer is present only opposite the bonding pad section.

Light modulator and method of manufacturing the light modulator

A semiconductor optical device includes a semiconductor laser region for producing laser light and having a first optical waveguide mesa structure including a first active layer and a diffraction grating, and first current blocking layers adjacent to opposite sides; a light modulator region for modulating the laser light and having a second optical waveguide mesa structure continuous with the first optical waveguide mesa structure and including a second active layer, and second current blocking layers adjacent to opposite sides; and a window region for propagating the laser light modulated by the light modulator region and having a mesa-shaped window structure continuous with the second optical waveguide mesa structure, the mesa width of the window structure being larger than the mesa width of the second optical waveguide mesa structure. The light is prevented from leaking from the window and reaching the interface of the window structure and a burying layer adjacent to the window structure. The laser light is not reflected at the interface of the window structure and the buried layer. The shape of the beam of laser light emitted from the window structure is not distorted, resulting in a satisfactory connection to an optical system.

Semiconductor optical device

A method of fabricating a semiconductor laser includes successively epitaxially growing on a first conductivity type semiconductor substrate, a first conductivity type lower cladding layer, an active layer, a second conductivity type first upper cladding layer having a relatively high etching rate in an etchant, a second conductivity type etch stopping layer having a relatively low etching rate in the etchant, a second conductivity type second upper cladding layer, and a second conductivity type first contact layer; forming a stripe-shaped mask on the first contact layer; removing portions of the first contact layer and the second upper cladding layer in a first wet etching step to expose the etch stopping layer; removing portions of the second upper cladding layer in a second wet etching step to form a stripe-shaped ridge structure having a reverse mesa cross section without an intermediate construction; growing a first conductivity type current blocking layer contacting both sides of the ridge structure; and after removal of the mask, growing a second conductivity type second contact layer on the current blocking layer and on the first contact layer. The angle between the side wall of the ridge and the etch stopping layer is an acute angle so the stripe-shaped ridge structure has a perfect reverse mesa cross section and is narrowest proximate the active layer.

Method of fabricating semiconductor laser

A semiconductor laser device includes a structure in which a first conductivity AlGaInP first cladding layer, an active layer, a second conductivity type AlGaInP second cladding layer, a second conductivity type AlGaInP intermediate layer, and a second conductivity type AlGaInP third cladding layer are successively epitaxially grown on a first conductivity type GaAs semiconductor substrate. The intermediate layer is within a profile of light produced in the active layer and includes AlGaInP layers having a band gap energy smaller than the band gap energy of the second cladding layer and the third cladding layer and larger than the band gap energy of the active layer. The intermediate layer has a multi-layer structure in which (Al.sub.x Ga.sub.1-x)InP layers (0.ltoreq.x.ltoreq.0.2) and (Al.sub.x Ga.sub.1-x)InP layers (0.5.ltoreq.x.ltoreq.1) are alternatingly laminated. By adding a small amount of Al to the intermediate layer, the band gap energy of the intermediate layer is broadened to control absorption of light emitted from the active layer and an increase in the threshold current of laser oscillation is suppressed. Since the intermediate layer has a multi-layer structure, a semiconductor laser device with sufficient etch stopping effect during etching of an off (100) substrate is realized.

Semiconductor laser device

In a semiconductor laser module wherein a semiconductor laser chip having a light emitting facet and an optical fiber having a fiber facet are mounted on a module substrate so that the light emitting facet faces the fiber facet, the semiconductor laser chip includes semiconductor layers disposed on a semiconductor substrate and including a light emitting region, and the semiconductor substrate has a portion protruding beyond the light emitting facet. The optical fiber includes a core extending in the optical waveguide direction and a cladding part surrounding the core. In this module, positioning of the optical fiber in the optical axis direction is performed by abutting a portion of the cladding part at the fiber facet against the protruding portion of the substrate of the semiconductor laser chip. Therefore, alignment of the optical fiber with the laser chip in the optical axis direction is performed easily and accurately with a desired spacing between them, without contacting the light emitting facet of the laser chip to the fiber facet, whereby coupling efficiency between the laser chip and the optical fiber is significantly improved.

Semiconductor laser module

A method of fabricating an integrated semiconductor laser device includes preparing a polygonal heat sink having side surfaces, and die-bonding semiconductor laser chips to the side surfaces of the heat sink. Therefore, the semiconductor laser chips are accurately arranged at such positions that laser beams emitted from these laser chips are parallel to each other and partially overlap each other. In addition, the semiconductor laser chips are integrated without unwanted contact of a conductive material used for the die-bonding to an active layer exposed at a facet of each laser chip. Further, since the complicated process of die-bonding a laser chip on another laser chip is dispensed with, the fabricating method is easily automated.

Growing community of inventors

Tokyo, Japan

Hitoshi Tada