Mitsui Chemicals, Inc.

Mitsui Petrochemical Industries, Ltd.

The Furukawa Electric Co., Ltd.

Tsuyoshi Fujimoto

Kiyofumi Muro

Yumi Naito

Satoru Okada

Yoshikazu Yamada

Takeshi Koiso

Atsushi Okubo

Yasuo Oeda

Shoji Ishizaka

Michio Ohkubo

Yutaka Ohki

Kouichi Igarashi

Yuji Yoshida

Atsushi Ohkubo

A semiconductor laser device emitting a laser beam having stable emitting wavelength and a multimode spectrum is provided. The semiconductor laser device is a Fabry-Perot type semiconductor laser device having a layer structure including an active layer of a quantum well structure, and emitting a laser beam having wavelength stabilized by an action of return light and having a multimode spectrum, wherein each well layer satisfies relation:&#x393;/&#x2266;1.3&#xd7;10nmwhere &#x393; and d(nm) are an optical confinement factor and a thickness of a well layer, respectively.

Semiconductor laser device and laser module using same

Semiconductor laser device

A real index guided semiconductor laser device includes an optical waveguide layer at least on one side of an active layer that has a band gap energy not less than that of the active layer; a cladding layer on an outer side of the optical waveguide layer that has a band gap energy not less than that of the optical waveguide layer; a refractive index control layer having a striped window, buried in the optical waveguide layer by selective growth; and a semiconductor layer formed in the optical waveguide layer by selective growth prior to the selective growth of the refractive index control layer. In a laminated portion including the semiconductor layer and the refractive index control layer, a change in effective refractive index due to a change in thickness of the semiconductor layer is smaller than that of the refractive index control layer.

On a substrate of n-type GaAs are sequentially formed an n-type cladding layer (AlGaAs, Al content x&equals;0.07, thickness t&equals;2.86 &mgr;m), an n-type optical waveguide layer (GaAs, t&equals;0.49 &mgr;m), an n-type carrier blocking layer (AlGaAs, x&equals;0.40, t&equals;0.03 &mgr;m), an active layer (composed of an In Ga As quantum well layer and a GaAs barrier layer), a p-type carrier blocking layer (AlGaAs, x&equals;0.40, t&equals;0.03 &mgr;m), a p-type optical waveguide layer (GaAs, t&equals;0.49 &mgr;m), a p-type cladding layer (AlGaAs, x&equals;0.20, t&equals;1.08 &mgr;m), and a p-type cap layer (GaAs) in which a pair of n-type current blocking layers (GaAs) are buried. With this construction, the occurrence of a wavelength spit due to a higher-order mode can be inhibited thereby stabilizing a higher power operation.

Semiconductor laser apparatus

A semiconductor laser device includes: an active layer; upper waveguide layers and a lower waveguide layer sandwiching the active layer therebetween; upper and lower cladding layers sandwiching the active layer and the upper and lower waveguide layers therebetween; and a current-narrowing layer defining a current-injection region for injecting current to the active layer, wherein a diffraction grating having a periodical structure in a resonance cavity direction is buried in any one of the waveguide layers, the diffraction grating being present in at least a part of the current-injection region; and the waveguide layer in which the diffraction grating is buried and the cladding layer adjoining to that waveguide layer forms an interface which is substantially flat in the resonance cavity direction. With the constitution, a waveguide structure which has a diffraction grating offering a higher flexibility in design and manufacture in terms of the coupling efficiency is realized, thereby easily providing a dynamic single-mode semiconductor laser device with higher reproducibility, yield and reliability.

Semiconductor laser device, semiconductor laser module, rare-earth-element-doped optical fiber amplifier and fiber laser

On an n-GaAs substrate are sequentially formed an n-GaAs buffer layer, an n-AlGaAs cladding layer, a non-doped InGaAs active layer, a p-Al,Ga,As cladding layer, a p-GaAs contact layer, and further an n-AlGaAs current blocking layer having a stripe-like window is embedded in the cladding layer. At the active layer side interface of the current blocking layer, a diffraction grating of cyclic bumps and dips shape is formed, but the diffraction grating is not formed in a region of the stripe-like window where the current blocking layer is not present, i.e., a current injection region. In this way, a semiconductor laser device of low oscillation threshold, high oscillation efficiency, high reliability, long life time, and stabilized oscillation wavelength can be realized.

Optical guide layers are formed on both faces of the active layer, respectively, which optical guide layers have a band gap wider than that of the active layer, an n-type cladding layer and a p-type cladding layer respectively formed so as to sandwich the active layer and the optical guide layers therebetween, which cladding layers have a band gap wider than those of the optical guide layers, and carrier blocking layers are respectively formed between the active layer and the optical guide layers, which carrier blocking layers have a band gap wider than those of the active layer and the optical guide layers. The refractive index of the p-type cladding layer is lower than that of the n-type cladding layer. With such constitution inner losses are limited to a low level, as free carrier absorption is reduced, and the electric and thermal resistances of a semiconductor laser device are reduced, with the result that the laser device is enhanced in efficiency and output power.

Method of fabricating semiconductor laser using selective growth

To overcome the dilemma on device design in control of waveguide mode experienced in the conventional weak wave-guide-laser and SCH structure laser, realize higher output and lower dispersion of radiation beam, and improve the waveguide mode, on both sides of an active layer, carrier blocking layers for reducing the waveguide function of the active layer are provided, and waveguide layers are provided on both outer sides of the carrier blocking layers, and cladding layers are provided on both outer sides of the waveguide layers, the active layer is lamination of side barrier layers and a quantum well layer sandwiched therebetween, or side barrier layers, and a quantum well layer and a barrier layer sandwiched therebetween, the composition of the quantum well layer is Ga.sub.y In.sub.1-y As (0.6&lt;y&lt;1.0), and the carrier blocking layers are made of a material having a wider band gap and a lower refractive index than the material of the waveguide layers.

A semiconductor laser of this invention, having a structure of an element composed of: carrier block layers, formed bilaterally externally of an active layer in section which is formed in the vertical direction from the surface of the element, for reducing a light guiding function of the active layer; wave guide layers provided bilaterally externally of said carrier block layers and clad layers provided so that the wave guide layers are sandwiched in between the clad layers. This invention overcomes a dilemma inherent in the conventional weakly guiding laser and LOC structured laser in terms of designing the device for controlling a guided mode. The present invention also solves the problems in terms of attaining higher outputting and a low dispersion of the radiation beams and improving a beam profile.

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Sodegaura, Japan

Tsuyoshi Fujimoto