Electronics and Telecommunications Research Institute

El-Hang Lee

Kyong-Hon Kim

O-Kyun Kwon

Hak-Kyu Lee

Sung-Bock Kim

Young-Wan Choi

Seo-Yeon Park

Jeong-Rae Ro

Kwang-Joon Kim

Kang-Ho Park

Jeong-Sook Ha

Min-Yong Jeon

Kyu-Seok Lee

Kyung-Sook Hyun

Joon-Tae Ahn

Seong-Ju Park

Jong-Dug Shin

Byueng-Su Yoo

Seok-Ho Song

Jong-Sool Jeong

Pyong-Woon Park

Wang-Yuhl Oh

Seon-Gyu Han

Wan-Soo Yun

Tae-Hyung Zyung

Jong-Tai Lee

Cheul-Shin Kang

Chong-Hoon Kwak

Seong-Bock Kim

For a multiple transmission communication system, how to individually isolate the transmitted lights and then to distribute to the terminals has been primary concerns to be solved. In the photodetector structure, an absorption layer may be configured as either multiple quantum well structures corresponding to operational wavelengths, or filter-based structure, allowing to select wavelengths in a 1:2:4:8 ratio as an absorptance for each wavelength. In case of using such four-fold lights, the determination as to which wavelength among four-fold wavelengths can be made based upon the total amounts of the current flow in such a photodetector. The photodetector employing such schemes is provided from the present invention.

Photodetector for simultaneous recognition of multiple wavelengths, and

A linear motion apparatus for moving an object in a vacuum chamber comprising an antenna or a telescoping shaft such as a fishing rod to effectively utilize space, and to avoid the need of a rear projection thereby achieving stability. The linear motion apparatus includes: a body having a space portion penetrated horizontally; a rotary handle which penetrates at a right angle to the space portion of the body thereby controlling a linear motion; locking portion which is mounted in the space portion of the body, is inserted into a shaft of the rotary handle, and used to lock the motion; a guide rod which is formed as a multistage rod, whose one end is inserted and fixed into a predetermined position of the space portion of the body; linear motion force providing portion whose one end is fixed to the rotary plate and the other end is fixed to a nose portion of the guide rod, thereby providing a linear motion force to the guide rod; and a bellows seal which surrounds a circumference of the guide rod, is shrunken or expanded according to a linear motion of the guide rod. As a result, this apparatus performs a linear motion control by a contraction and expansion under ultra high vacuum.

Linear motion apparatus under ultra high vacuum

An epitaxial growth method for a compound semiconductor thin film, capable of forming a p-n junction with an atomic-scale ultra-micro structure is disclosed. The method involves loading the compound semiconductor substrate in a reaction chamber, injecting Group V and III metal organic source gases not processed by a thermal pre-decomposition process into the reaction chamber, and growing a p- or n-type compound semiconductor on the compound semiconductor substrate while adjusting the growth temperature of the p- or n-type compound semiconductor.

Formation of InGaSa p-n Junction by control of growth temperature

Disclosed is a fabricating method of a GaAs substrate having a V-shaped groove in a higher density, that is a double density, the method comprising the steps of forming a Si.sub.3 N.sub.4 layer on a main surface of the GaAs substrate; patterning the Si.sub.3 N.sub.4 layer using a photo-lithography to form a patterned Si.sub.3 N.sub.4 layer having a minimum width; wet-etching the GaAs substrate using the patterned Si.sub.3 N.sub.4 layer as a mask, so as to form (111) and (100) surfaces of the GaAs substrate beneath the patterned Si.sub.3 N.sub.4 ; selectively growing a GaAs film on the GaAs substrate etched thus using the patterned Si.sub.3 N.sub.4 layer as a mask so as to form the GaAs film with two (111) facets only on a (100) surface of the GaAs substrate; and removing the Si.sub.3 N.sub.4 layer. The V-shaped grooves can be formed on a GaAs substrate utilizing a difference of growth rate caused by surface orientation of the substrate, and therefore the grooves can be formed in double density.

Fabricating method of GaAs substrate having V-shaped grooves

A dual cavity laser having a positively mode-locked structure capable of double increasing the repetition rate of output light. The dual cavity laser includes an amplitude modulator to simultaneously generate two modulating signals with opposite phases. The dual cavity laser has a simply modified structure from that of the conventional single cavity laser to have two resonators, so that it can have a repetition rate corresponding to two times that of the single cavity laser. One of the resonators may have an adjusted optical property so as to obtain two kinds of output optical pulses with different optical properties.

Dual cavity laser

A pulsed semiconductor laser has a lower threshold current and a more stable pulse train. The structure includes a saturable absorber section has a quantum well structure for laser oscillation, a gain section, a phase control section, and a super structure grating-distributed Bragg reflector section. It uses an improved construction for overcoming problems of conventional pulsed semiconductor lasers. The improved structure includes five quantum well layers having thicknesses with respective spontaneous emission peak wavelengths of '.lambda.-2.delta.', '.lambda.+.delta.', '.lambda.+2.delta.', '.lambda.', '.lambda.-.delta.' at room temperature from their upper section. .lambda. denotes the mean wavelength of the oscillating pulse laser, and .delta. denotes a fixed value less than 12 nm. The super structure grating-distributed Bragg reflector section has five sampling sections, with each section having five kinds of different pitches arranged in order of thicknesses of 25 cycles, 5 cycles, 25 cycles, 5 cycles, and 25 cycles.

Semiconductor laser device for pulse laser oscillation

A measurement of nonlinear refractive index coefficient of an optical fiber with a Sagnac interferometer, comprises the steps of employing the optical fiber in a Sagnac interferometer, splitting a signal beam into two signals, launching the two split signals into the interferometer in opposite directions, combining and detecting the signals counter-propagated in the interferometer, and detecting the refractive index coefficient of the optical fiber in accordance with the difference between the two signal powers determined by a control beam. The quasi-static phase shift of the signal beam counter-propagating the same paths of the interferometer is induced by rotating the optical fiber loop of the interferometer. The present invention gives rise to little error because it does not require precise information about the pulse width of a used beam or a high-power light.

Measurement of nonlinear refractive index coefficient of optical fiber

A crystal growth method for a compound semiconductor is capable of forming a plurality of quantum wells (formed of a barrier layer having a large energy band gap and an active layer having a small energy band gap) on the compound semiconductor substrate. After etching a V-shaped groove having a (111) surface with a predetermined angle .theta.1 with respect to the (100) surface on the GaAs semiconductor substrate, the substrate is further etched by a hydrochloric solution and a solution of H.sub.2 SO.sub.4 :H.sub.2 O.sub.2 :H.sub.2 O=20:1 to cause the V-shaped groove walls to become a non-(111) surface having a lower predetermined slope angle .theta.2. The quantum wells then grown in the bottom of the V-shaped groove will be effectively disconnected from simultaneous growths on the side walls of the groove thus giving rise to closely controlled multi-dimensional quantum well structures.

Crystal growth method for compound semiconductor

A vertical modulator with a dual mode distributed Bragg reflection (DBR), includes a pair of integrated elements using different wavelengths to provide functions of logical operation, data switching and wavelength conversion. The optical device includes a first optical structure operating at a first wavelength (.lambda..sub.1) and a second optical structure operating at a second wavelength (.lambda..sub.2). The first and second optical structures are formed over a semiconductor substrate. The first optical structure, which operates at the first wavelength (.lambda..sub.1), transmits its data to the second optical structure so that data corresponding to the second wavelength (.lambda..sub.2) can be output. Since the wavelength of input light is different from the wavelength of output light, the optical device serves as a modulator which performs a logic operation and switching function while carrying out wavelength conversion.

Vertical modulator with dual mode DBR

An optical fiber laser is disclosed capable of generating an ultrashort pulse which has intensive energy and is stable against polarization by using a sagnac loop mirror and a Faraday rotator mirror, which includes a light pumping laser diode; an erbium doped fiber-added optical fiber; a wavelength division multiplier fiber coupler; a dispersion shifted fiber; and an optical fiber directional coupler; a nonlinear amplifier loop mirror; a second polarization controller; a linear mirror having a Faraday rotator mirror for rotating the polarization plane of a proceeding light wave; and a directional coupler being connected between the nonlinear amplifier loop mirror and the linear mirror.

Optical fiber laser

A wavelength division demultiplexing device, and a system using the device are disclosed, in which there is utilized a Pabry-Perot etalon using as a spacer layer a Kerr medium in which the refractive index is varied in accordance with the intensity of beams. The wavelength division demultiplexing device according to the present invention includes: a substrate; a first mirror layer formed on the substrate, and consisting of an alternately repeating medium used as a bottom mirror layer; a second mirror layer consisting of an alternating repeating stack of a high refractive index medium and a low refractive index medium used as a top mirror layer; and a spacer layer composed of a Kerr medium and disposed between the first mirror layer and the second mirror layer; wherein the reflectivity of the first mirror layer is higher than that of the second mirror layer; and the thickness of the spacer layer is set such that the value of the initial tuning phase of the spacer layer for the range of wavelengths of an incident beam is m.pi.+t.pi., where m represents an integer, and t represents 0.2-0.4.

Wavelength division demultiplexing device, and system using it

A method for the manufacture of a single electron transistor (SET) in a vacuum state, wherein the SET operates in room temperature, comprises the steps of: approaching an Au tip of a scanning tunneling microscopy (STM) on top of a silicon-substrate having a silicon oxide layer on top thereof to maintain a distance from top of the oxide layer to end of the Au tip of the STM; forming an Au cluster on top of the oxide layer by using a low field evaporation method employing the STM, thereby forming a two dimensional island structure on top of the oxide layer, wherein the low field evaporation method employing the STM generates an electronic pulse between top of the oxide layer and end of the Au tip of the STM by applying a voltage to the Au tip of the STM; forming a source and a drain to both sides of the Au cluster in the two dimensional island structure, respectively, in such a way that the Au cluster in the two dimensional island structure maintains a gap with the source and the drain, thereby forming an electron tunneling barrier on right and left of the Au cluster in the two dimensional island structure; and joining a gate on bottom of the silicon-substrate.

Method for manufacturing a single electron transistor by using a

Disclosed is a nonbiased bistable optical device and a method for fabricating the device, which has a semi-insulating GaAs substrate; a lower mirror having a plurality of reflecting layers which are repeatedly formed on said substrate at least more than twelve times, each of said reflecting layers having a first reflecting film having a first refractive index on said substrate and a second reflecting film a second refractive index different from the first refractive index; a first contact layer formed on the lower mirror; a first buffer layer formed on the first contact layer; a multiple quantum well(MQW) having a plurality of shallow layers which are repeatedly formed, each of said shallow layers having a barrier and a shallow quantum well; a second buffer layer grown on said MQW; and a second contact layer formed on said second buffer layer. The device has an excellent bistablity even without an external applied voltage.

Nonbiased bistable optical device having a lower mirror having a

An all-optical signal processing apparatus of a non-linear fiber loop mirror type comprises a very high-speed all-optical switch that can be used as a reverse multiplexed switch in a high-speed time division optical communication. The apparatus includes a non-linear loop mirror for switching signal light by adjusting light using the non-linear effect of an optical fiber and the characteristics of a sagnac interferometer as the fundamental configuration. The all-optical switch is constructed so that another adjustment light having an appropriate time delay with respect to an existing adjusting light is additionally introduced in order to compensate for the limitation on the switching bandwidth imposed by the walk-off between adjusting and signal lights in a conventional non-linear optical fiber loop mirror. This compensates for the cross-talk of the noise signals due to DC components generated in the conventional apparatus. A switching window of a desirable size is obtained by properly adjusting the time delay between two adjusting lights and resolving the bandwidth limitation of the switch due to the walk-off of the adjusting and signal lights according to the timing jitter of signal light.

All-optical signal processing apparatus of non-linear fiber loop mirror

A bidirectional multi-channel all-optical ring network is provided, this network comprising a number of nodes linked by optical cables, each of the node comprising two of WDM/WDDM, packet switching devices, and a node controller, in which network a first optical signal group of wavelength channel signals (for example, .lambda.1, .lambda.3, .lambda.5, . . . ) are transferred in a counter-clockwise direction, and a second optical signal group of wavelength channel signals (for example, .lambda.2, .lambda.4, .lambda.6, . . .) are transferred in a clockwise direction, thereby allowing an optical data signal to be transmitted through the channel of shorter distance.

Growing community of inventors

Daejeon, South Korea

El-Hang Lee