Gwangju Institute of Science and Technology

Samsung Electronics Co., Ltd.

Kwangju Institute of Science and Technology

Jong-In Song

Chang-soo Park

Yong-hwa Park

Yong-chul Cho

Jae-hyung Jang

Hyoung-Jun Kim

An optoelectronic shutter, a method of operating the same, and an optical apparatus including the optoelectronic shutter are provided. The optoelectronic shutter includes a phototransistor which generates an output signal from incident input light and a light emitting diode serially connected to the phototransistor. The light emitting diode outputs output light according to the output signal, and the output signal is gain-modulated according to a modulation of a current gain of the phototransistor.

Optoelectronic shutter, method of operating the same and optical apparatus including the optoelectronic shutter

An optical modulator, methods of manufacturing and operating the same, and an optical apparatus including the optical modulator are disclosed. The optical modulator includes an electro-optical converter and an optical-electric converter, stacked perpendicular to a substrate, and a gate transistor. The gate transistor gates a signal transmitted to the electro-optical converter from the optical-electric converter and allows charges generated in the optical-electric converter and charges remaining in the electro-optical converter to flow while bypassing the electro-optical converter when gating ON is performed.

Optical modulator, methods of manufacturing and operating the same and optical apparatus including the optical modulator

Disclosed is an all-optical frequency upconverter in a radio-over-fiber system that outputs upconverted optical radio frequency (RF) signals using an optical intermediate frequency signal and an optical local oscillation signal. The all-optical frequency upconverter includes a semiconductor optical amplifier that mixes the optical intermediate frequency signal with the optical local oscillation signal through four wave mixing, and an optical filter that filters a plurality of frequency component signals, which are generated through the four wave mixing, to extract optical RF signals. According to the invention the system configuration can be made simple, and wide LO and IF frequency bandwidths can be provided.

All-optical frequency upconverter and all-optical frequency upconversion method in radio-over-fiber system

The monolithically integrated Enhancement/Depletion mode HEMT (high-electron-mobility transistor) of the present invention comprises: a buffer layer, a channel layer, a spacer layer, a first barrier layer, a second barrier layer, a third barrier layer, and an ohmic layer consecutively formed on a semiconductor substrate from bottom to top; the first exposed region (a gate region for a Depletion-mode HEMT) formed by selective etching of the ohmic layer to expose the third barrier layer; a second exposed region (a gate region for an Enhancement-mode HEMT) formed by selective etchings of the ohmic layer and the third barrier layer to expose the second barrier layer; and gate electrodes formed on the first and second exposed gate regions. According to the present invention, a monolithically integrated Enhancement/Depletion mode HEMT having a uniform threshold voltage can easily be fabricated. The second barrier layer, which has a larger bandgap energy compared with those of other barrier layers and is used for the fabrication of an Enhancement-mode HEMT, plays a role of increasing the potential barrier height with respect to the gate electrode metal. The increased potential barrier height can make the total thickness of barrier layers required for the threshold voltage of the Enhancement-mode HEMT device thicker than that of a conventional Enhancement-mode HEMT. This improves the speed characteristic of the Enhancement-mode HEMT since the transistor has a decreased gate capacitance.

Growing community of inventors

Daejeon, South Korea

Jong-In Song