Fujitsu Corporation

The University of Tokyo

Manabu Matsuda

Tsuyoshi Yamamoto

Yuji Kotaki

Hajime Shoji

Mitsuru Ekawa

Ayahito Uetake

Kan Takada

Shouichi Ogita

Hiroshi Ishikawa

Kazumasa Takabayashi

Yasuhiko Arakawa

Nobuaki Hatori

Takuya Fujii

Koji Otsubo

Shigekazu Okumura

Takeshi Matsumoto

Tatsuroh Ikeda

An optical element includes a distributed Bragg reflector, wherein the distributed Bragg reflector includes a first-order diffraction grating of a first-order period disposed in a central region, and second-order diffraction gratings of a second-order period having a coupling coefficient smaller than a coupling coefficient of the first-order diffraction grating and disposed in both end regions between which the central region is located.

Optical element, optical module, and optical transmission system

A semiconductor laser in a ridge waveguide structure includes: a semiconductor substrate; a lower cladding layer which is formed on the semiconductor substrate; an active layer and a semiconductor layer which are in parallel on the lower cladding layer and are connected with each other; a first upper cladding layer locally aligned above the active layer; a second upper cladding layer locally aligned above the semiconductor layer; and a third upper cladding layer locally aligned above the active layer to confine light which is guided in the active layer, wherein the semiconductor layer has a band gap which is larger than that of the active layer. According to this constitution, an optical semiconductor device with high reliability in which the ridge waveguide structure whose manufacturing is relatively easy is applied, and current diffusion and electrical crosstalk between lasers in the ridge waveguide structure are suppressed is enabled.

Optical semiconductor device and manufacturing method thereof

An optical semiconductor device includes: an active region which includes an active layer which produces light when current is injected therein, a first diffraction grating layer having a first diffraction grating with a prescribed grating period, and a phase shift portion formed within the first diffraction grating layer, wherein the phase shift portion provides a phase shift not smaller than 1.5&#x3c0; but not larger than 1.83&#x3c0;; and a distributed reflection mirror region which is optically coupled to a first end of the active region as viewed along a direction of an optical axis, and which includes a second diffraction grating which reflects the light produced by the active region back into the active region.

Optical semiconductor device, optical semiconductor device array, and optical transmitter module

A tunable laser includes: a wavelength filter that includes a first ring resonator and a second ring resonator each of which is formed by a waveguide including a silicon waveguide core, and each of which is capable of shifting each of resonance wavelengths that exit periodically and whose intervals are different from each other; and an integrated device that is optically coupled to the wavelength filter, and in which a first semiconductor optical amplifier and a reflector are provided in sequence from a side of the wavelength filter, wherein the resonance wavelengths of the first ring resonator and the second ring resonator are overlapped with each other at one wavelength, and the resonance wavelengths are overlapped with each other also at a plurality of wavelengths other than the one wavelength.

Tunable laser and tunable laser module

An optical device includes an active layer disposed over a semiconductor substrate, a diffraction grating disposed over the active layer, a clad layer partly disposed over the diffraction grating, at least one first burying material layer disposed beside side surfaces of end portions of the clad layer over the diffraction grating, and at least one second burying material layer disposed beside side surfaces of a center portion of the clad layer over the diffraction grating. A refractive index of the at least one first burying material layer is different from a refractive index of the at least are second burying material layer.

Optical device and optical module

A method for manufacturing a semiconductor light emitting device includes forming a lower cladding layer over a GaAs substrate; forming a quantum dot active layer over the lower cladding layer; forming a first semiconductor layer over the quantum dot active layer; forming a diffraction grating by etching the first semiconductor layer; forming a second semiconductor layer burying the diffraction grating; and forming an upper cladding layer having a conductive type different from that of the lower cladding layer over the second semiconductor layer, wherein the processes after forming the quantum dot active layer are performed at a temperature not thermally deteriorating or degrading quantum dots included in the quantum dot active layer.

Semiconductor light emitting device and method for manufacturing the same

A semiconductor laser includes an active region including an active layer, and a diffraction grating and a phase shift which determine an oscillation wavelength, and a distributed reflector region including a light guide layer and a refection diffraction grating. The distributed reflector region has an effective diffraction grating period which varies along a direction of a cavity.

Semiconductor laser

An optical device includes: an optical waveguide; and a plurality of diffraction grating layers, provided along the optical waveguide, each including a diffraction grating defined by a discontinuous first semiconductor layer and a second semiconductor layer having a refractive index different from a refractive index of the first semiconductor layer and burying the first semiconductor layer, one diffraction grating layer of the plurality of diffraction grating layers including a third semiconductor layer being continuous with the diffraction grating and made from a material different from materials of the first and the second semiconductor layers.

Optical element and method for manufacturing the same

An optical semiconductor device is disclosed including an active region including an active layer and a diffraction grating having a &#x3bb;/4 phase shift; passive waveguide regions each including a passive waveguide and a diffraction grating, disposed on the side of an emission facet and on the side of a rear facet sandwiching the active region between the passive waveguide regions, respectively; and an anti-reflection coating applied on the emission facet, wherein the passive waveguide region on the side of the emission facet has a length shorter than a length of the passive waveguide region on the side of the rear facet side.

Optical semiconductor device and method for manufacturing the same

A semiconductor laser includes an active layer, a first GaAs layer formed on the active layer, the first GaAs layer including a plurality of recessed portions periodically arranged, each of the recessed portions including a bottom surface of a (100) crystal surface and a slope including a (111) A crystal surface at least in parts, the recessed portion being disposed in contact with each other or with a minimal gap between each of adjacent ones of the recessed portions, the width of the bottom surface being greater than the minimal gaps, an InGaP layer formed on the recessed portion, and a second GaAs layer formed on the InGaAs layer over the recessed portion.

An optical semiconductor device includes an active layer, a first semiconductor layer formed above the active layer and made from a semiconductor material containing Al, a second semiconductor layer formed above the first semiconductor layer and made from a semiconductor material which does not contain any one of Al and P and whose band gap is greater than that of the active layer, and a third semiconductor layer formed above the second semiconductor layer and made from a semiconductor material which does not contain Al but contains P. The second semiconductor layer is formed such that the first semiconductor layer and the third semiconductor layer do not contact with each other.

Optical semiconductor device

An optical device including: an optical waveguide; and a plurality of diffraction grating layers provided along the optical waveguide, wherein each of the diffraction grating layers comprises a diffraction grating, each diffraction grating comprising a discontinuous first semiconductor layer and a second semiconductor layer burying the first semiconductor layer, the first and second semiconductor layers having different refractive indices, the plurality of diffraction grating layers comprise at least two diffraction grating layers being different from each other in terms of the length of a region where the diffraction grating is provided, and the diffraction gratings in an overlap region of the plurality of diffraction grating layers have the same phase and period is provided.

Optical device and method for manufacturing the same

In a semiconductor laser, in order to realize a desired oscillation wavelength efficiently by adjusting the oscillation wavelength of the laser with sufficient accuracy even when the oscillation wavelength of a manufactured laser deviates from a design value, for example, due to the manufacturing errors and the like in the manufacturing of the laser, there is provided a semiconductor laser comprising a semiconductor substrate, a semiconductor stacking body including a waveguide formed on the semiconductor substrate, and a diffraction grating, wherein the diffraction grating is formed along the waveguide so as to appear in the surface of the semiconductor stacking body.

Semiconductor laser and manufacturing method thereof

An optical waveguide structure formed over a substrate defines an optical waveguide for guiding light along a direction parallel to the substrate surfaces, and biasing a light intensity distribution of transverse modes of guided wave toward a first side of the optical waveguide path. A main diffraction grating is disposed at least on a second side opposite to the first side, and coupled with the guided wave propagating along the optical waveguide. A subsidiary diffraction grating is disposed on the first side, and diffracts the guided wave coupled with the main diffraction grating and propagating along the optical waveguide, to a direction different from an extending direction of the optical waveguide.

Optical device having diffraction gratings coupling guided wave, and its manufacture method

An optical waveguide propagates a laser beam. Main diffraction grating and sub-diffraction grating couple light propagating in the optical waveguide. The main diffraction grating and the sub-diffraction grating couple the light in such a manner that propagation in a second order transverse mode of the light propagating in the optical waveguide when both the main diffraction grating and the sub-diffraction grating are disposed, is suppressed more than propagation in the second order transverse mode of the light propagating in the optical waveguide when only the main diffraction grating is disposed.

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Kawasaki, Japan

Manabu Matsuda