Hitachi, Ltd.

Hitachi Maxell, Limited

Jun-ichi Umeda

Takashi Kajimura

Michiharu Nakamura

Takao Kuroda

Kunio Aiki

Shigeo Yamashita

Hisao Nakashima

Hiroshi Matsuda

Kazuo Shigematsu

Naoki Chinone

Toshikazu Shimada

Masayoshi Kobayashi

Yoshifumi Katayama

Motohisa Hirao

Noriyuki Shige

Yasutoshi Kashiwada

Katsutoshi Saito

Kazutoshi Saito

An optical recording disc comprising a resin layer of resin material formed on a relatively rough surface of each transparent disc substrates, the resin material having approximately the same refractive index of light as the refractive index of the transparent disc substrate, and a recording layer formed on each of said resin layers. Accordingly, the optical recording disc enables a decrease in production costs and to write and read an information signal into and from the recording layer at an improved signal to noise ratio as compared to a conventional optical recording disc.

Unit and disc having a relatively rough surface and method of producing

A semiconductor laser device is provided with a semiconductor substrate and at least a semiconductor assembly for optical confinement formed on the substrate which includes an active layer and cladding layers. A first electrode is disposed on the semiconductor assembly and a second electrode is disposed on the semiconductor substrate. To provide a phase-locked semiconductor laser device of high quality, a plurality of regions are provided in the semiconductor assembly which, in effect, cause a variation of a complex refractive index for a laser beam in a direction intersecting with a traveling direction of the laser beam. These regions can be discretely disposed over or under the active layer and give rise to a nonlinear interaction between adjacent laser emission regions formed by the plurality of regions.

Phase-locked semiconductor laser device

A phase-locked semiconductor laser device comprising a laminated structure in which a plurality of first semiconductor layers having the substantially same composition are stacked in a manner to be sandwiched between second semiconductor layers having a band gap wider, and a refractive index lower, than those of said first semiconductor layers; a third semiconductor layer which is disposed in contact with at least one of side faces of said laminated structure parallel to a traveling direction of a laser beam, which is not narrower in the band gap and not higher in the refractive index than said first semiconductor layers and which does not have the same conductivity type as, at least, that of said first semiconductor layers; means to inject current into an interface between said first semiconductor layers and said third semiconductor layer disposed on the side face of said laminated structure; and means to act as an optical resonator for the laser beam.

In a semiconductor laser device having at least a first semiconductor layer, second and third semiconductor layers which are formed in a manner to sandwich the first semiconductor layer and which have a wider band gap and a lower refractive index than those of the first semiconductor layer, an optical resonator and carrier injection means; a semiconductor laser device characterized in that at least said first semiconductor layer has an angle of inclination (.theta.) relative to an axis which is perpendicular to optically flat faces constituting said optical resonator. The inclination angle .theta. (rad) should most preferably lie in a range of: ##EQU1## where .theta..sub.z denotes a reflection angle, .theta..sub.c a critical angle, W 1/2 of a thickness of a waveguide, and l a cavity length. The laser device is effective for preventing laser facets from breaking down, and can produce high power.

Semiconductor laser device

In a semiconductor laser device wherein a stripe-shaped impurity-diffused region is disposed in at least parts of semiconductor layers of from a surface semiconductor layer of a semiconductor layer assembly constituting the semiconductor laser device to a second semiconductor layer lying in contact with a first semiconductor layer having an active region, the impurity-diffused region having the same conductivity type as that of the second semiconductor layer and extending at least from the surface semiconductor layer to a depth vicinal to the first semiconductor layer, the impurity region serving as a current path; a semiconductor laser device characterized in that a third semiconductor layer in which the diffusion rate of an impurity for use in the formation of the impurity-diffused region is lower than in the second semiconductor layer is disposed between the surface semiconductor layer and the second semiconductor layer.

A semiconductor laser device of this invention has a built-in passive guiding mechanism along the junction plane by growing planar double hetero (DH) layers on a grooved or projected substrate. It operates stably in the lowest transverse mode and provides light-output versus current characteristics free of either kinks or any anomalies.

Disclosed is a semiconductor laser element having on a predetermined semiconductor substrate a stacked region for optical confinement including an active layer and clad layers, a first electrode disposed on the semiconductor substrate side and a second electrode disposed over the stacked region, and means for constructing an optical resonator, the semiconductor laser element comprising the fact that the means to inject current into the active layer is formed of a plurality of stripe conductive regions which are juxtaposed in traveling direction of a laser beam, and that laser radiations emitted in correspondence with the respective stripe conductive regions form a simply connected net and give rise to nonlinear interactions among them. As a typical example of the current injection means, the conductive regions have a strip-shaped pattern which includes a broader portion and a narrower portion. A coupled-multiple-stripe laser element in which the phases and wavelengths of the laser radiations of the respective strips are uniform is realized.

A semiconductor laser element is disclosed which includes a film of an amorphous material deposited on at least an optical output facet of the laser element and contains silicon and hydrogen as the indispensable components. The thickness of the amorphous film is preferably selected in the vicinity of (.lambda./4).multidot.m where .lambda. represents wavelength of laser light in the amorphous film and m represents an odd integer. A film of a transparent insulation material can be deposited over the amorphous film thereby to constitute a composite film. With the disclosed structure of the semiconductor laser element, increasement in a threshold current of the laser element can be suppressed to a minimum, while a maximum optical output power can be increased.

Semiconductor laser device with facet passivation film

A semiconductor laser device of this invention has a built-in passive guiding mechanism along the junction plane by growing planar double hetero (DH) layers on a grooved or projected substrate. It operates stably in the lowest transverse mode and provides light-output versus current characteristics fee of either kinks or any anomalies.

In certain applications, it is desirable to have a semiconductor laser device having shorter wave lengths of oscillation than are possible with conventional semiconductor lasers. To accomplish this, a semiconductor laser device is formed having a double-hetero structure, which comprises a semiconductor substrate composed of a GaAsP crystal, a first cladding layer formed on the substrate and composed of a GaAlAsP crystal of one conducting type, an active layer formed on the first cladding layer and composed of GaInAsP crystal, and a second cladding layer formed on the active layer and composed of a GaAlAsP crystal of the conducting type reverse to that of the first cladding layer. The cladding layers disposed on both sides of the active layer have a lower refractivity and a larger band gap than the active layer.

A semiconductor laser device has stabilized longitudinal and transverse modes without excess optical noise for a modulated signal generated by mode interaction. The fundamental construction of the semiconductor laser device comprises a structure wherein a first semiconductor layer is sandwiched between second and third semiconductor layers which have a greater band gap and lower index of refraction than the first semiconductor layer. That region of at least one of the second and third semiconductor layers which is remote from the first semiconductor layer corresponds substantially to a radiation region and serves as a light non-absorptive region in the shape of a stripe. A semiconductor layer has portions lying on both sides of the semiconductor layer remote from the first semiconductor layer and has an effective complex refractive-index for laser light discontinuous at both ends of the semiconductor layer remote from the first semiconductor layer. Periodic corrugations which intersect orthogonally to the lengthwise direction of the stripe-shaped light non-absorptive region are formed in at least one interface of the semiconductor layers in a manner to include at least a region corresponding to the light non-absorptive region.

A semiconductor laser device capable of emitting highly collimated beams, especially of a narrow beam divergence, is disclosed. A striped hetero-junction is formed on a predetermined semiconductor substrate by a first semiconductor layer (refractive index: n.sub.1, band gap: Eg.sub.1, thickness: d), a second semiconductor layer (n.sub.2) and a third semiconductor layer (n.sub.3), and the hetero-junction is sandwiched between portions of a fourth semiconductor layer (n.sub.4, Eg.sub.4) into a buried structure. At this time, the various materials are selected to follow the relations of d.ltoreq..lambda. (where .lambda. denotes the oscillation wavelength of the semiconductor laser), n.sub.2, n.sub.3 &lt;n.sub.4 &lt;n.sub.1, and Eg.sub.1 &lt;Eg.sub.4, and the effective refractive index of the first semiconductor layer (n.sub.1eq) is made smaller than n.sub.4.

Growing community of inventors

Hachioji, Japan

Jun-ichi Umeda