Nec Corporation

Nippon Electric Co., Ltd.

Mitsunori Sugimoto

Ichiro Ogura

Kenichi Kasahara

Yoshiharu Tashiro

Keiichi Kubota

Shigeru Kawai

Kaori Kurihara

Hidenori Nomura

An optical device has a multi-layer reflecting structure provided in association with an active layer for allowing light to oscillate, and the multi-layer reflecting structure is implemented by a plurality of units each having a high refractive film, a low refractive film and a layer for improving conductivity of the multi-layer reflecting structure, wherein the layer is implemented by a heavily doped impurity region with an impurity profile tracing plots of a delta function or by a quasi-graded super-lattice film microscopically graded in composition between the high and low refractive films.

Optical device with low-resistive multi-level reflecting structure

A semiconductor optical memory includes a gate layer composed of a p- first semiconductor layer, a p- or n- second semiconductor layer, and an n- third semiconductor layer provided between a cathode layer and an anode layer. Where the second layer is of n- type, an impurity concentration of the n- second semiconductor layer is lower than an impurity concentration of the n- third semiconductor layer, and a bandgap eneray of the n- third semiconductor layer is lower than bandgap energies of the cathode and anode layers. Where the second layer is of p- type, an impurity concentration of the p- second semiconductor layer is lower than an impurity concentration of the p- first semiconductor layer, and a bandgap energy of the p- first semiconductor layer is lower than bandgap energies of the cathode and anode layers. As a result, a response speed becomes as fast as several 100 Mb/s.

Semiconductor optical memory having a low switching voltage

A space modulation matrix is composed of semiconductor transmittivity modulation elements arranged in a matrix pattern. A transmittivity of the transmittivity modulation elements is changed by supplying a light or applying a voltage greater than a switching voltage of the transmittivity modulation elements to a selected number of the transmittivity modulation elements, so that a space modulation is provided on the space modulation matrix, and is renewed by any number of times.

Semiconductor device for a space modulation matrix and method for

An improved phototransistor device comprises a collector region and a base region respectively provided on the opposite sides of a multiple quantum well, and an emitter region provided on one side of the base region. A reverse-biased voltage is applied across the multiple quantum well while incident light is input to be absorbed in the multiple quantum well thereby producing photocurrent therein. In the improved phototransistor device, a higher photocurrent level is obtained in accordance with the amplification thereof even if the incident light is very small in its power.

Phototransistor device

An improved semiconductor laser comprises an active region of quantum well, at least two cladding layers positioned at both sides of said active region, and two electrodes provided separately at one side of at least one cladding layer of said at least two cladding layers so that a laser oscillation is produced in a wide wavelength range and high response rate for the reason why the wavelength of a laser oscillation can be changed in wavelengths in the vicinity of transition energy E.sub.ke-HH between n=k electron quantum and n=k heavy hole quantum level (k=1, 2, 3 - - - ) in accordance with the control of current to be injected from one electrode of said two electrodes or voltage to be applied to said one electrode.

Semiconductor laser with a variable oscillation wavelength

According to the present invention, an active semiconductor layer is provided on a mesa top of a semiconductor substrate having a strip-shaped mesa structure. A first clad layer is provided on the surface of the active layer and on the sides of the mesa to burry the top active region. Thereafter a pair of current blocking layers are provided on the first clad layer except for the top surface portion of the mesa stripe and a second clad layer is provided on the current blocking layers and the exposed first clad layer.

Growing community of inventors

Tokyo, Japan

Mitsunori Sugimoto