著者

Kenichi IGA Yasushi TAKAHASHI

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS (1976-1990) (ISSN:00000000)

巻号頁・発行日

vol.E61-E, no.9, pp.685-689, 1978-09-25

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In this paper, an analysis was made on the variation of oscillating mode numbers of a semiconductor laser at high speed pulse modulation by solving multi-mode rate equations which relate a quasi-Fermi level to photon numbers. The laser gain was assumed to be homogeneous and has a dependency of (), where is ωEg (relative photon energy). Single mode oscillation conditions for short pulse modulation were obtained associated with following two cases. A) One is the criterion how wide the mode separation must be made as of a short cavity laser and of an integrated twin-guide (ITG) laser. B) The other is the condition how large we must give an excess loss to the unwanted modes such as of the ITG laser, of a distributed feedback (DFB) laser, and of a distributed Bragg reflector (DBR) laser.

著者

Fumio KOYAMA Susumu KINOSHITA Kenichi IGA

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS (1976-1990) (ISSN:00000000)

巻号頁・発行日

vol.E71-E, no.11, pp.1089-1090, 1988-11-25

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This is the first report on room temperature CW operation of GaAlAs/GaAs vertical Fabry-Perot cavity surface emitting lasers. A vertical microcavity was formed with a diameter of 7 µm and cavity length of 5.5 µm by a two-step MOCVD growth and fully monolithic technology. The threshold current was 32 mA under CW condition at 22.5. Stable single transverse and longitudinal mode operation was obtained.

著者

Noboru MURAYAMA

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS (1976-1990) (ISSN:00000000)

巻号頁・発行日

vol.E72-E, no.5, pp.661-669, 1989-05-25

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A polynomial for automatic contour vector coding of the binary picture pattern is proposed. The proposed polynomial is the expansion of the Bezier polynomial to have the more flexibility. It is easy to be implemented and the generated curve is easy to be estimated from the given control points. This advantage is confirmed by the automatic contour coding of both English and Japanese fonts.

著者

Ryoichi MORI Masaji KAWAHARA

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE TRANSACTIONS (1976-1990) (ISSN:00000000)

巻号頁・発行日

vol.E73-E, no.7, pp.1133-1146, 1990-07-25

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Superdistribution is an approach to distributing software in which software is made available freely and without restriction but is protected from modifications and modes of usage not authorized by its vendor. By eliminating the need of software vendors to protect their products against piracy through copy protection and similar measures, superdistribution promotes unrestricted distribution of software. The superdistribution architecture we have developed provides three principal functions: administrative arrangements for collecting accounting information on software usage and fees for software usage; an accounting process that records and accumulates usage charges, payments, and the allocation of usage charges among different software vendors; and a defense mechanism, utilizing digitally protected modules, that protects the system against interference with its proper operation. Superdistribution software is distributed over public channels in encrypted form. In order to participate in superdistribution, a computer must be equipped with an S-box--a digitally protected module containing microprocessors, RAM, ROM, and a real-time clock. The S-box preserves secret information such as a deciphering key and manages the proprietary aspects of the superdistribution system. A Software Usage Monitor insures the integrity of the system and keeps track of accounting information. The S-box can be realized as a digitally protected module in the form of a three-dimensional integrated circuit.