Hitachi, Ltd.

Atsutoshi Doi

Shinji Tsuji

Takao Mori

Michiharu Nakamura

Motohisa Hirao

Satoshi Nakamura

Naoki Chinone

Kunio Aiki

Ryoichi Ito

Yutaka Takeda

A buried-heterostructure semiconductor laser including a mesa-shaped optical confinement region having an active layer and a clad layer and disposed on a semiconductor substrate; a burying layer burying both side surfaces of the region; and at least one p-n junction so formed inside the burying layer in parallel to the active layer as to be brought under the reversely biased state during the operation of the laser; wherein surface protection semiconductor layers are formed on the mesa-shaped optical confinement region and on the burying layer, respectively, for protecting the semiconductor assembly in the arrangement such that these surface protection semiconductor layers do not come into direct contact with each other. Even if the forbidden band gas of these surface protection semiconductor layers are relatively small, it is possible to realize a semiconductor laser having an extremely small leakage current and reduced variance of threshold current values, while protecting the surface of the multi-layer semiconductor layers.

Semiconductor laser device

Disclosed herein is a semiconductor laser device including at least an active region consisting of a semiconductor material and a semiconductor region consisting of a material having a different composition from that of the active region and confining the active region, wherein at least one p-n junction is formed inside the confining region in parallel to the active region and a current flowing through the active region at a field strength below an electric field causing degradation of the semiconductor laser device is allowed to flow through regions other than the active region via the p-n junction by controlling the impurity concentration of the region having the p-n junction. The semiconductor laser device does not undergo catastrophic degradation even when applied with a current higher than a rated value.

Semiconductor laser device including an arrangement for preventing laser

A semiconductor laser device is formed of a semiconductor material assembly including a first semiconductor layer having an active region formed directly by crystal growth on a substrate for the crystal growth having on the surface thereof a second semiconductor layer. A third semiconductor layer is also formed on the first layer. The refractive index of each of the second semiconductor material region and the third semiconductor layer is smaller than that of the first semiconductor layer while the band gap of each of the second semiconductor material region and the third semiconductor layer is broader than that of the first semiconductor layer. In order to provide mode stabilization even at long wavelength, the thickness of the active region formed at the interface between said first semiconductor layer and said substrate for crystal growth is made larger than the thickness of the other portions in the first semiconductor layer so that the effective refractive index to laser beams is changed stepwise in a direction perpendicular to the direction of the laser beams.

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Ohme, Japan

Atsutoshi Doi