Abstract: A solar cell and method of fabricating the same are provided. The solar cell includes a metal electrode layer, an optical absorption layer, a buffer layer, and a transparent electrode layer. The metal electrode layer is disposed on a substrate. The optical absorption layer is disposed on the metal electrode layer. The buffer layer is disposed on the optical absorption layer and includes an indium gallium nitride (InxGa1-xN). The transparent electrode layer is disposed on the buffer layer.

Abstract: Provided are a method and device for separating and converting multiband signals. The device includes a photoelectric converter for converting an externally received optical signal into an electrical signal, a first switch for separating the converted electrical signal into signals according to frequency bands, a first mobile communication band-pass amplifier for amplifying a mobile communication network signal of the signals separated by the first switch, a broadband up-converter for up-converting a baseband signal of the signals separated by the first switch into a broadband signal, a first broadband amplifier for amplifying the broadband signal output from the broadband up-converter, and a transmitter for wirelessly transmitting the signals amplified by the first mobile communication band-pass amplifier and the first broadband amplifier.

Abstract: An electroabsorption (EA) duplexer in which an optical amplifier, a photodetector, and an optical modulator are monolithically integrated to obtain a high radio frequency (RF) gain in radio-over fiber (RoF) link optical transmission technology is provided. The EA duplexer includes a substrate, a separation area, an optical detection/modulation unit, and an optical amplification unit. The separation area includes a first epitaxial layer formed of at least one material layer on the substrate. The first epitaxial layer functions as a first optical waveguide. The optical detection/modulation unit includes a second epitaxial layer formed of at least one material layer on the first epitaxial layer to detect and modulate an optical signal. The second epitaxial layer functions as a second optical waveguide. The optical amplification unit includes the second optical waveguide and a third epitaxial layer formed of at least one material layer on the second epitaxial layer to amplify an optical signal.

Abstract: Provided is an optical module used in a communication system employing a radio over fiber (ROF) technology delivering a radio frequency (RF) signal through an optical fiber. The optical module includes: an optical device; a signal line for transporting a radio frequency (RF) signal input from an external circuit to the optical device; and a resistor separately disposed from the signal line and having one end connected with the optical device, wherein the input impedance seen from the signal line is matched by the resistor. A bias voltage supplied to operate the optical device is applied through an inductor connected to the signal line between the optical device and a filter. Here, the filter formed by a pattern of the signal line prevents the bias voltage from being supplied to the external circuit. In order to amplify the RF signal input from the external circuit, an amplifier may be connected between the external circuit and the filter.

Abstract: Provided is an optical hybrid module in which an optical device, a filter, an amplifier and an antenna are hybrid-integrated, which includes: a silicon optical bench disposed on a substrate and having an optical fiber and an optical device; an amplifier disposed on the substrate and connected to the optical device disposed on the silicon optical bench to amplify a signal transmitted from the optical device; and an antenna disposed on the substrate to be connected to the amplifier and transmitting a signal amplified by the amplifier. Thus, a foot-print module may be embodied by disposing an antenna and a filter on a single- or multi-layer substrate and providing a bias required for the optical device and the amplifier through a solder ball. Also, due to the antenna and filter disposed on the substrate, an expensive connector is not needed, and thus a production costs can be reduced.

Abstract: Provided is a reflection-type optical modulation module. According to the reflection-type optical modulation module, an anti-reflective thin film is formed on the optical input/output side surface of a waveguide to reduce optical coupling loss, and also a high-reflective thin film is formed on the opposite side surface to feed back a modulated optical signal. Thus, even when the length of an absorption layer is shortened, a sufficient optical path length is available, and it is possible to obtain a sufficient extinction ratio. Since the optical path length is sufficiently long despite a reduction in the length of the device, capacitance is reduced, and high-speed operation is enabled. In addition, only one lensed optical fiber for optical input and output is used, and thus it is possible to reduce production cost and the number of installation processes.

Abstract: Provided is a double waveguide electroabsorption modulator, in which two spot size converters are integrated between first and second optical waveguides, thereby reducing an insertion loss between an optical fiber and an optical modulator while favorably operating even in high input optical power. Therefore, the electroabsorption modulator can stably operate in higher input optical power while reducing an optical coupling loss and an optical confinement factor (OCF).

Abstract: Provided is an optical module including a microstrip line, a traveling wave type optical device positioned in the end of the microstrip line, and at least one balanced open stub connected to the microstrip line for the impedance matching at a specific frequency such as 40 GHz and 60 GHz. For the fine tuning, laser trimming can be applied to the stub. A transition region is formed between the optical device and the microstrip line. A termination resistor is formed to face the microstrip line with the optical device therebetween. A bandwidth can be controlled at a specific frequency by adjusting a number of the stubs or a value of the termination resistor.

Abstract: An electroabsorption (EA) duplexer in which an optical amplifier, a photodetector, and an optical modulator are monolithically integrated to obtain a high radio frequency (RF) gain in radio-over fiber (RoF) link optical transmission technology is provided. The EA duplexer includes a substrate, a separation area, an optical detection/modulation unit, and an optical amplification unit. The separation area includes a first epitaxial layer formed of at least one material layer on the substrate. The first epitaxial layer functions as a first optical waveguide. The optical detection/modulation unit includes a second epitaxial layer formed of at least one material layer on the first epitaxial layer to detect and modulate an optical signal. The second epitaxial layer functions as a second optical waveguide. The optical amplification unit includes the second optical waveguide and a third epitaxial layer formed of at least one material layer on the second epitaxial layer to amplify an optical signal.