Abstract: A laser diode and an optical switching device are connected in parallel relative to a power supply. The optical switching device is turned on by receiving an input light, and stores the ON state, so that the laser device is turned off. As a result, an electric power consumption is decreased, the structure is simplified, and the adjustment becomes easy.

Abstract: 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.

Abstract: A circuit for driving a gated p-n-p-n device comprises a p and/or n-gate electrodes provided on a p and/or n-gate regions of a p-n-p-n device, and a rectifying device provided between the p or n-gate electrode provided on a gate region which is higher in its impurity density than the other gate region and an anode or cathode electrode of the p-n-p-n device and/or a resistance means provided between the p or n-gate electrode provided on a gate region which is lower in its impurity density than the other gate region. In the circuit for driving a gated p-n-p-n device, excess carriers are expelled from the p and/or n-gate electrodes through the rectifying device and/or resistance means to the external of the p and/or n-gate regions.

Abstract: An optical semiconductor device comprises cathode and anode regions, and a gate region having a forbidden band gap narrower than those of the cathode and anode regions. The gate region is sandwiched by the cathode and anode regions. The optical semiconductor device further comprises a plurality of windows for receiving and radiating lights so that the alignment of light axes can be easily performed for a plurality of input and output lights.

Abstract: A process for controlling an optical pnpn thyristor to be driven comprises a step of applying a train of pulses to maintain a low impedance state of an optical pnpn thyristor which is shifted beforehand to be in the low impedance state by a positive set pulse. Each of the train of pulses is less than in its level than the positive set pulse. When light emission is required for the reading of an information, a positive set pulse is applied to the optical pnpn thyristor. As a result, electric power consumption is reduced during a time storing the information.

Abstract: A pnpn thyristor comprises an anode and cathode region, and a base region which is positioned between the anode and cathode regions. The base region is composed of a p-base layer facing the cathode region, and a first to third n-base layers. Among the first to third n-base layers, the first n-base layer faces the p-base layer, and the third n-base layer faces the anode region. The anode and cathode regions are wider in their forbidden bandwidth than the first and third n-base layers, and the second n-base layer is narrower in its forbidden bandwidth than the first and third n-base layers so that an optical coupling property is improved, and a high output of light is obtained.