Abstract: Filter-free wavelength converters for separating and rejecting an optical input signal. A first input port couples a continuous wave (CW) light. A second input port couples an optical input signal. A multimode interference semiconductor optical amplifier (MMI-SOA) determines the output port with the input port and intensity-modulation of the CW light with the optical input signal. A first output port guides the converted signal, and a second output port guides the optical input signal.

Abstract: The present invention relates to all-optical OR and XOR logic elements employing saturable absorbers as optical gates. Saturable absorbers are arranged in paths of the Mach-Zehnder interferometer, respectively. If the total power of an input optical signal and a continuous wave signal is higher than a transparent input power of the saturable absorbers, the input optical signal passes through the saturable absorbers, and then the optical signals through the two paths are combined, so that it is possible to obtain the operational characteristics of the OR and XOR logic elements. According to the present invention, unlike the optical logic element using a cross-phase modulation by a semiconductor optical amplifier, phase difference depending upon the input optical power is not generated between two paths, so that it is possible to alleviate a restriction of an allowable range of the input optical power.

Abstract: The present invention relates to an optical deflector driven by an electrical signal, and a wavelength tunable external resonator using the same. The optical deflector of a triangle shape, capable of controlling the refractive index of a beam depending on the electrical signal, is positioned between a reflection mirror and a diffraction grating in a Littman-Metcalf mode external resonator or between a lens and the diffraction grating in a Littrow mode external resonator. Thus, even with the reflection mirror and the diffracting grating fixed, the refractive index of the beam generated from a laser diode can be controlled by adjusting the electrical signal applied to the optical deflector, so that beam having a specific wavelength can be focused and the wavelength can be rapidly and consecutively tuned.

Abstract: Disclosed is a tunable wavelength semiconductor laser diode which comprises a FP(fabry-parrot) laser diode array for producing at least two light beams, a combiner for combining the light beams output by an end of the laser diode array, a lens for collimating the light beams output by another end thereof, a grating for diffracting the light beams collimated by the lens, and a reflector for reflecting the light beams diffracted by the grating to feed the reflected light beams back to the laser diode array.

Abstract: Disclosed is a high speed optical signal processor which includes a saturable absorber area including a substrate, an active layer, a clad layer and a first upper electrode which are sequentially formed on one face of the substrate, and a first lower electrode formed on the other face of the substrate; and a gain-clamped optical amplifier area including a substrate having a diffraction grating for generating a laser beam, an active layer, a clad layer and a second upper electrode which are sequentially formed on one face of the substrate, and a second lower electrode formed on the other face of the substrate, the second upper electrode being isolated from the first upper electrode of the saturable absorber area.

Abstract: The present invention relates to all-optical OR and XOR logic elements employing saturable absorbers as optical gates. Saturable absorbers are arranged in paths of the Mach-Zehnder interferometer, respectively. If the total power of an input optical signal and a continuous wave signal is higher than a transparent input power of the saturable absorbers, the input optical signal passes through the saturable absorbers, and then the optical signals through the two paths are combined, so that it is possible to obtain the operational characteristics of the OR and XOR logic elements.

Abstract: The present invention relates to an optical signal processing element capable of performing various functions of equalization of output power, wavelength converting, reshaping or reamplifying an input optical signal using an optical amplifier in which saturable absorbers are integrated, the saturable absorbers being used as an optical gate to improve the extinction ratio of the input optical signal. The saturable absorber and the optical amplifier are connected in series, and a transparent output optical power outputted from the saturable absorber is not less than a saturation input optical power of the optical amplifier.

Abstract: The present invention relates to a spot size converter and a method of fabricating the same, which provides efficient coupling between an optical fiber and integrated devices of optical waveguide. The spot size converter has an input and output optical waveguides formed in a vertical double-layer structure. Integrated to the output optical waveguide, an unidirectional side-tapered optical waveguide is formed. Due to the tapered structure of the optical waveguide, the effective refective index gradually changes along the length of the waveguide. Thus, the spot size of the optical signal gradually changes while the optical signal travels within the tapered optical waveguide. Therefore, the present invention effectively eliminates or minimizes the coupling loss and the reflection loss between the optical fiber and the devices connected to the spot size converter.

Abstract: Disclosed is a method for the fabrication of a spot-size converter with a lateral-tapered waveguide (or an active layer), which utilizes a mask during a lithographic process wherein the mask has a pad that can absorb strain to be occurred during forming a lateral-tapered waveguide pattern at its distal end and the lateral-tapered waveguide is fabricated by forming the distal end on the order of about 0.6 &mgr;m in width followed by forming the lateral-tapered waveguide on the order of 0.1 &mgr;m using an wet etching. Thus, it is possible to reduce a fabrication cost because it is free from a high-resolution electron beam lithography and a stepper, and hence enhance a reproducibility of the lateral-tapered waveguide because it is free from an excessive wet etching during the use of a contact exposure equipment.

Abstract: It is necessary to use the continuous wave (CW) light and the optical input signal in the same direction in order to improve the conversion speed. Furthermore, in order to simplify the configuration of the optical transmission system including wavelength converters, the function capable of separating or removing the optical input signal should be included. Filter-free wavelength converters for separating and rejecting the optical input signal are being developed using the multimode interference semiconductor optical amplifier (MMI-SOA). The gain or phase modulation of the CW light is caused in the MMI-SOA. Furthermore, the CW light and the optical input signal are separated in the MMI-SOA in which the output port depends on the input port. Therefore, no optical filter is required for rejecting the optical input signal, and it is possible to converse to the same wavelength.

Abstract: A semiconductor optical device with a differential grating formed by a holography method and a method for manufacturing the same are provided. The provided semiconductor optical device includes an n-type InP substrate, a stack structure on the InP substrate having a waveguide and active layers, a first grating formed under the stack structure and on the InP substrate, and a second grating formed on the stack structure. The provided method for manufacturing the semiconductor optical device forms a first grating on the n-type InP substrate and under the active layer, and forms a second grating on the active layer. The first and second gratings are formed by the holography method.

Abstract: The present invention relates to an optical filter whose a sidelobe disturbing a characteristic of an optical filter by weighting an optical coupling efficiency between waveguides is controlled upon applying a selective area growth method in a wavelength selective variable semiconductor optical filter and method of fabricating the same. The present invention can control the thickness of growth layer selectively by controlling the width of the dielectric thin film mask whose the growth is not achieved in the selective area growth method, can control the distance between two waveguides of the wavelength selective variable semiconductor optical filter by applying the result on the distance control between two waveguides. Accordingly, there can be changed an optical coupling efficiency between two waveguides spatially.

Abstract: The present invention relates to a method of manufacturing a semiconductor optical device. The present invention discloses a method of manufacturing an optical device of a planar buried heterostructure (PBH) type by which an active layer region of a taper shape at both ends is patterned, an undoped InP layer is selectively grown in order to reduce the propagation loss and two waveguides are simultaneously formed by means of a self-aligned method, thus simplifying the process to increase repeatability and yield.

Abstract: The present invention relates to an optical deflector driven by an electrical signal, and a wavelength tunable external resonator using the same. The optical deflector of a triangle shape, capable of controlling the refractive index of a beam depending on the electrical signal, is positioned between a reflection mirror and a diffraction grating in a Littman-Metcalf mode external resonator or between a lens and the diffraction grating in a Littrow mode external resonator. Thus, even with the reflection mirror and the diffracting grating fixed, the refractive index of the beam generated from a laser diode can be controlled by adjusting the electrical signal applied to the optical deflector, so that beam having a specific wavelength can be focused and the wavelength can be rapidly and consecutively tuned.

Abstract: Disclosed is a method for the fabrication of a spot-size converter with a lateral-tapered waveguide (or an active layer), which utilizes a mask during a lithographic process wherein the mask has a pad that can absorb strain to be occurred during forming a lateral-tapered waveguide pattern at its distal end and the lateral-tapered waveguide is fabricated by forming the distal end on the order of about 0.6 &mgr;m in width followed by forming the lateral-tapered waveguide on the order of 0.1 &mgr;m using an wet etching. Thus, it is possible to reduce a fabrication cost because it is free from a high-resolution electron beam lithography and a stepper, and hence enhance a reproducibility of the lateral-tapered waveguide because it is free from an excessive wet etching during the use of a contact exposure equipment.

Abstract: The present invention relates to a spot size converter and a method of fabricating the same, which provides efficient coupling between an optical fiber and integrated devices of optical waveguide. The spot size converter has an input and output optical waveguides formed in a vertical double-layer structure. Integrated to the output optical waveguide, an unidirectional side-tapered optical waveguide is formed. Due to the tapered structure of the optical waveguide, the effective refective index gradually changes along the length of the waveguide. Thus, the spot size of the optical signal gradually changes while the optical signal travels within the tapered optical waveguide. Therefore, the present invention effectively eliminates or minimizes the coupling loss and the reflection loss between the optical fiber and the devices connected to the spot size converter.

Abstract: Disclosed is a method for fabricating an optical integrated circuit capable of obtaining a current confinement and a maximum opto-coupling efficiency by using a simple process, in a case where an active device such as an optical waveguide and an optical amplifier. The method comprises a step for growing layers constituting the optical device over an InP substrate, a step for etching the grown layers by use of a wet etching method or a dry etching method of RIE along a plane perpendicular to a (001) plane, and a step for growing a core layer and a clad layer of the waveguide to be optically connected by use of a molecular organic chemical vapor deposition.

Abstract: Disclosed is an optical switch device for totally reflecting an incident light therein in accordance with a change in refractive index occurring owing to current application, which is manufactured by the steps of: sequentially forming an optical waveguide layer, an n-InP clad layer and an n-InGaAs cap layer on a main surface of an n-InP substrate using an epitaxial growing; selectively etching the n-InGaAs cap layer to form an opening tapered downward; diffusing an impurity into the n-InP clad layer through the opening and into the n-InGaAs cap layer to a predetermined depth from a surface thereof so as to form a first impurity diffused region in the n-InP clad layer under the opening and to form a second impurity diffused region along the surface of the n-InGaAs cap layer; etching the layers on the optical waveguide layer using a mask to form a ridge-shaped waveguide; and forming electrodes on the n-InGaAs cap layer and an exposed surface of the n-InP clad layer and on a surface which is opposite to the main

Abstract: The present invention relates to an integrated photoelectric receiving device in which a PIN-type photodetector and a junction field effect transistor (FET) are integrated in a single chip. The photoelectric receiving device comprises a photodetector having a n-channel layer, an etching stopper layer and an absorption layer formed on a semi-dielectric substrate, the n-channel layer, the etching stopper layer and the absorption layer being formed in a reverse mesa shape and the substrate being etched by a predetermined depth; a transistor having a n-channel layer, an etching stopper layer and a p-type InP layer sequentially formed on the non-etched portion of the semi-insulator substrate, the p-type InP layer having an absorption layer formed thereon in a reversedmesa shape. Also, the invention contemplates a method of manufacturing the device.