• Current Optics and Photonics
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• v.3 no.6
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• pp.577-582
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• 2019

We report on a continuous-wave (cw) optical parametric oscillator (OPO) optimized for mid-infrared emission above 5.0 ㎛. The OPO is based on a magnesium-oxide-doped periodically poled LiNbO₃(MgO:PPLN) crystal with a fan-out grating design. A linear two-mirror cavity resonating both at the pump and signal wavelengths is stabilized to the pump laser by using the modified Pound-Drever-Hall (PDH) method. The idler wavelength is continuously tunable from 4.7 ㎛ up to 5.3 ㎛ by varying the poling period of the fan-out grating crystal. Pumped by a diode-pumped solid state (DPSS) laser with a power of 1.1 W at 1064 nm, the maximum idler output power is measured to be 5.3 mW at 4.8 ㎛. The output power above 5.0 ㎛ is reduced to the hundreds of ㎼ level due to increased absorption in the crystal, but is stable and strong enough to be measured with a conventional detector.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.6
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• pp.658-663
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• 2015

In the previous work, we have proposed an integrate-and-fire neuron circuit and synaptic device based on the floating body MOSFET [1-3]. Integrate-and-Fire(I&F) neuron circuit emulates the biological neuron characteristics such as integration, threshold triggering, output generation, refractory period using floating body MOSFET. The synaptic device has short-term and long-term memory in a single silicon device. In this paper, we connect the neuron circuit and the synaptic device using current mirror circuit for summation of post synaptic pulses. We emulate spike-timing-dependent-plasticity (STDP) characteristics of the synapse using feedback voltage without controller or clock. Using memory device in the logic circuit, we can emulate biological synapse and neuron with a small number of devices.

• Journal of the Korean Society of Costume
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• v.32
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• pp.69-82
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• 1997

The purpose of this study was to investgate the social meaning and consumption values expressed on apparel advertisements In Teena-ger's magazines from 1976 to 1996. The results of this study were as follows. 1. As the number of the model in apparel advertisements was more than two people it was closely related to conformity and peer ac-ceptance of adolecent's developmental task. Also There were increasing number of foreign models and attractive and famous signers and talents. 2. The trend of appeals showed changing time and society. Since 1990 post-modern ap-proach has increased whereas rational and emotional approach were dominated in 1970s and 1980s. 3, The major consumption values in apparel advertisements were social value emotional value. From 1990 there were variety in consumption values related to adolescent's ap-parel advertisements. This results represented the possibility that apparel advertisements in adolescent's maga-zines not only mirror but mold change of con-sumption values and life style in adolescent. Especially to understand and predict the new generation in Korea educators and practi-tioners in Junior Fashion Market must try to study the current adolescent's life style and consumption values systematically.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1641-1644
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• 2005

현재의 인터넷과 같은 전자 통신망과 멀티미디어 시스템의 발달은 고속의 대용량 데이터 전송을 필요로 한다. 초고속 통신 시스템에서의 고속 데이터 전송은 주로 광섬유를 사용하는 광통신으로 이루어지고 있다. FTTH(Fiber To The Home)와 같은 광통신 시스템은 멀티미디어 커뮤니케이션을 위해 필요한 큰 데이터 전송률을 제공할 수 있기 때문에 더욱 더 중요성이 높아지고 있으며 이러한 광통신 시스템에서는 통신환경의 영향을 적게 받고 외부 조절이나 부품이 필요하지 않는 수신기 IC 의 개발이 요구되고 있다. 일반적으로 광통신 수신기에는 고속 동작에 적합한 특성을 가진 GaAs-MESFET 가 사용되고 있으나, 본 논문에서는 0.35um CMOS 2-poly 4-metal 공정을 이용하여 5Gbps 광수신기를 설계하였다. 설계된 수신기는 Preamplifier, Main amplifier, ABC 회로로 구성되어 있다. Transimpedance amplifier 형태의 Preamplifier 는 광검출기에 의해 생성된 전류 신호를 전압 신호로 변환한다. ABC 회로는 Peak_Hold 회로와 Bottom_Hold 회로로 구성되어 있다. 기존의 Peak_Hold 회로에서는 다이오드와 hold capacitor 를 이용하여 peak 값을 검출하도록 되어 있는데, 다이오드를 이용하는 경우 작은 입력 신호전압의 Peak 값을 검출하는 데 한계가 있다. 이러한 단점을 보완하고자 전류 거울형태의 Peak_Hold 회로를 설계하였다. 전류거울(current mirror)형태의 출력 신호의 duty error 를 줄이고 비트 에러율(Bit Error Rate)을 개선하는데 효과적이었다. 설계된 광수신기는 30dB 의 입력 dynamic range 와 입력 capacitance 3pF 에서 80MHz 의 대역폭을 가진다. 전력 소비량은 3.3V 전원 전압이 인가된 경우 약 150mW 정도이다.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.12
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• pp.64-72
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• 2003

This paper presents a small loading and positioning device using VCM (voice coil motor). The developed device consists of a VCM-based linear actuating system, a capacitance displacement sensor and a cantilever deflection sensing system. The trust force of the VCM proportional to applied current moves the column supported on two pairs of parallel leaf springs. The infinitesimal displacement of moved column is detected by capacitance displacement sensor with a resolution of 0.1nm and a repeatability of 1nm. Also, a micro cantilever with known stiffness (200N/m), which is mounted on the end of the column, is used as a force sensor to detect the load applied to a specimen. After the cantilever contacts with the specimen, the deflection of cantilever and the load applied to the specimen are measured by using an optical lever system which consists of a diode laser, a mirror and a PSD (position sensitive detector). In this paper, an experimental system was constructed and its actuator and sensing parts were tested and calibrated. Also, the constructed system was applied to the indentation experiment and the load-displacement curve of aluminum was obtained. Experimental results showed that the developed device can be applied for performing nano indentation.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.195-201
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• 2005

A laterally driven electromagnetic microactuator (LaDEM) is presented, and a micro-optical switch is designed and fabricated as a possible application. LaDEM provides parallel actuation of the microactuator to the silicon substrate surface (in-plane mode) by the Lorentz force. Poly-silicon-on-insulator (Poly-SOI) wafers and a reactive ion etching (RIE) process were used to fabricate high-aspect-ratio vertical microstructures, which allowed the equipment of a vertical micro mirror. A fabricated arch-shaped leaf spring has a thickness of $1.8{\mu}m$, width of $16{\mu}m$, and length of $800{\mu}m$. The resistance of the fabricated structure fer the optical switch was approximately 5$\Omega$. The deflection of the leaf springs increases linearly up to about 400 mA and then it demonstrates a buckling behavior around the current value. Owing to this nonlinear phenomenon, a large displacement of $60{\mu}m$ could be measured at 566 mA. The displacement-load relation and some dynamic characteristics are analyzed using the finite element simulations.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.257-262
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• 2001

A Littman type tunable external-cavity diode laser system was developed. The laser output which is the Oth-order diffracted beam from a diffraction grating in an external cavity is a single longitudinal mode. Its FWHM was measured as less than 9 MHz. With the diode driving current of 140 mA and operating temperature of $25^{\circ}C$, the coarse tuning range of 3.475 urn was measured. A fine tuning experiment in which an external mirror was rotated by a PZT driven by a sawtooth wave was performed, and its tuning range of 0.042 urn was measured. sured.

• Current Optics and Photonics
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• v.2 no.4
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• pp.348-355
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• 2018

How to measure the creepage distance of an insulator quickly and accurately is a problem for the power industry at present, and the noticeable concern is that the high voltage insulation equipment cannot be measured online in the charged state. In view of this situation, we develop an on-line measurement system of creepage distance for high voltage insulators based on binocular stereo vision. We have proposed a method of generating linear structured light using a conical off-axis mirror. The feasibility and effect of two ways to solve the interference problem of strong sunlight have been discussed, one way is to use bandpass filters to enhance the contrast ratio of linear structured light in the images, and the other way is to process the images with adaptive threshold segmentation and feature point extraction. After the system is calibrated, we tested the measurement error of the on-line measurement system with a composite insulator sample. Experimental results show that the maximum relative error is 1.45% and the average relative error is 0.69%, which satisfies the task requirement of not more than 5% of the maximum relative error.

• Current Optics and Photonics
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• v.2 no.4
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• pp.356-360
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• 2018

We demonstrate continuous-wave operation of an all-fiber thulium-holmium codoped laser operating at a wavelength of 1706.3 nm. To realize laser operation in the short-wavelength region of the emission-band edge of thulium in silica fiber, we employ fiber Bragg gratings having resonant reflection at a wavelength around 1700 nm as a wavelength-selective mirror in an all-fiber cavity scheme. We first examine the performance of the laser by adjusting the central wavelength of the in-band pump source. Although a pump source possessing a longer wavelength is observed to provide reduced laser threshold power and increased slope efficiency, because of the characteristics of spectral response in the gain fiber, we find that the optimal pump wavelength is 1565 nm to obtain maximum laser output power for a given system. We further explore the properties of the laser by varying the fiber gain length from 1 m to 1.4 m, for the purpose of power scaling. It is revealed that the laser shows optimal performance in terms of output power and slope efficiency at a gain length of 1.3 m, where we obtain a maximum output power of 249 mW for an applied pump power of 2.1 W. A maximum slope efficiency is also estimated to be 23% under these conditions.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.3
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• pp.201-210
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• 2002

This paper describes a 3.3 (V) low power 4 digit CMOS quaternary to analog converter (QAC) designed with a neuron MOS($\upsilon$MOS) down literal circuit block and cascode current mirror source block. The neuron MOS down literal architecture allows the designed QAC to accept not only 4 level voltage inputs, but also a high speed sampling rate quaternary voltage source LSB. Fast settling time and low power consumption of the QAC are achieved by utilizing the proposed architecture. The simulation results of the designed 4 digit QAC show a sampling rate of 6(MHz) and a power dissipation of 24.5 (mW) with a single power supply of 3.3 (V) for a CMOS 0.35${\mu}{\textrm}{m}$ n-well technology.