• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.152-156
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• 1999

We have developed the pulse-width variable Quenched Dye Laser (QDL). QDL consisted of the dye cell of 5 mm length containing a $2.5{\times}10^{-3}$[mol/l] solution of Rhodamine 6G and the cylindrical lens focal length of 150 mm and quenching mirror. QDL system was pumped by s XeCl excimer laser with 150 mJ pulse energy in a 20 ns pulse at 1 Hz repetition rate. Pulse-width of QDL was measured by a noncollinear intensity autocorrelator. The focused thckness was measured by changing the position of the focusing cylindrical lens. Pulse-width of QDL as a function of the focused thickness (273.0${\mu}{\textrm}{m}$~845.0${\mu}{\textrm}{m}$) varied continuously from 86 ps to 201 ps.

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.512-517
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• 1999

Quenched dye laser (QDL), which operates with relaxation oscillation mode, is one of the most powerful source for ultra-short pulse light. In this paper, the output characteristics of QDL is theoretically analyzed by a computer simulation. The QDL is assumed that the laser dye is Rhodamine 6G which has the oscillation wavelength of 590 nrn and that the active length is 5 mm and that the pumping source is XeCllaser which has oscillation wavelength of 308 nm. It is revealed ilim the pulse width of short cavity dye laser reduced less than 1/100 than pumping pulse duration and has the linear relationship with spatial width of pumping beam approximately. In addition, it is revealed that the short cavity dye laser is a powerful candidate of pulse width variable light source, which is adjusted by spatial size of pumping beam_ beam_

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.430-438
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• 1999

We have utilized soft-aperturing by gain media to develop a high-power tunable Ti:Sapphire laser with sub-40-fs and broad tuning range. The tunable spectral range was only limited by the bandwidth of mirrors. We made use of knife-edge slits near an intra-cavity prism controlled by micro-stepping-motors to tune the center wavelength continuously. The tunability of the center wavelength was ranged from 770 nm to 870 nm, and the measured pulsewidth was sub-40 fs throughout the above spectral range. The shortest pulsewidth was about 17 fs at the center wavelength of 820 nm and the spectral bandwidth was 72 nm. At 5 W pumping power of the Ar-ion laser we obtained average output power of 440 mW~580 mW. For the cw and Kerr-lens mode-lodking conditions, we have evaluated the value of an amplitude modulation to be ${\gamma}=2.5{\times}10^{-8}/W$ from the calculated waists of a Gaussian beam on the Ti:sapphire crystal surface. Using this result we demonstrate that the generation of sub-40-fs Kerr-lens mode-locked pulse can be described by the Ginzberg-Landau model which is a weak pulse shaping model.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.117-117
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• 2013

레이저 레이더용 시력안전파장대 고출력 광펄스 생성을 위한 광원으로 MOPA 구도로 광섬유 레이저를 제작 하였다. MOPA 기반 펄스 광섬유 레이저는시력 안정 파장대인 1,550 nm 대역 파장을 갖고 펄스폭이 2 ns 이하이며 반복률이 30~240 kHz 가변 가능하다. 광섬유 증폭단에서 1단 증폭기는 저잡음용 코어 펌핑 방식의 증폭기로 구현하였으며, 2단 증폭기는 중출력 증폭기로 코어 펌핑구조에 후방향 펌핑 구도로 설계하였다. 3단 증폭기는 최종목표인 2ns 이하의 펄스 폭 및 25 kWp 이상의 첨두출력을 달성하기 위하여 클래딩 펌핑 방식의 고출력 광증폭기로 구현하였다.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.68-72
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• 1999

We demonstrate a new pulse characterization scheme relying on self-heterodyning that uses intracavity frequency shifter in a fiber soliton laser with frequency shifted feedback. By heterodyning the frequency-shifted pulse stream with the unshifted one, and by measuring the beat strength with varying the delay length between two pulse streams, we obtain the amplitude autocorrelation function from which we estimate the pulsewidth. The result is in good agreement with that obtained by the autocorrelation relying on the second harmonic generation.

• 전기의세계
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• v.25 no.4
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• pp.38-41
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• 1976

최근 전력용 반도체소자를 이용하여 전력의 변환과 제어를 하는 Power electronics가 많은 발전을 하고 있는데 이것을 가장 많이 이용하는 분야는 전동기의 가변속 구동이다. 이중에서 교류전동기의 구동을 위한 가변 주파수 제어장치의 구성을 보면 전압형 Inverter, 전류형 Inverter 및 Cycloconverter등에 의한 것으로 대별된다. 교류전동기의 가변주파수 제어는 농형유도전동기의 경우가 가장 많고 동기전동기는 약간 있는 정도이다. 여기서는 이러한 제어에 쓴이는 전압형 Inverter의 대표적인 회로와 최근에 개발된 펄스폭 제어 Inverter의 동작 원리 및 특징등에 대하여 소개하고저 한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.942-948
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• 2011

Solid propulsion systems have simple structures compared to other propulsion systems and are suitable for long-term storage. However the systems generally have limits on control of thrust levels. In this paper we introduce controllers for combustion chamber pressure using on-off control techniques which have been known for relatively easy implementation and energy efficiency. For this, we use a simple pressure change model by considering only mass conservation within the combustion chamber and we design a classical controllers and on-off controllers with are Pulse Width Modulation(PWM) and Pulse Width Pulse Frequency Modulation (PWPFM). Then we compare the performance results of the controllers through numerical simulations.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.266-267
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• 2004

LED를 이용한 차량용 signal lamp를 구현 하였다. 가변적인 전원전압 및 온도조건에서도 일정한 광량을 유지할 수 있도록 하였으며, 한편 단위 LED 사이의 특성 차이로 인한 밝기의 불균일성을 줄일 수 있도록 하기 위하여 펄스폭 변조를 응용한 회로를 적용하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.81-87
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• 2021

In this study the skin care system was designed and tested by introducing V-IPL(Variable-Intense Pulse Light) methods that allow various skin treatments. The discharge method, a new method of switching on the flash lamp sequentially according to the lesions, was used. Pulse shape control is implemented in the system using the conventional LC variable method and the switching method control method of the switching element. As a result, the pulse width could be varied up to 1[㎛] by using a microprocessor, and by turning on the flash lamp sequentially along the lesions the depth and width, the pulse shape and pulse shape could be more diverse. We could also make long pulses of up to 1~100[ms] in various pulse width. And the special differences between the existing system and the proposed system in this study are as follow. Existing system is one pulse(pulse width : 1~40ms) and proposed system is three pulse(pulse width : 1~100ms).

• Journal of IKEEE
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• v.5 no.2 s.9
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• pp.201-210
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• 2001

Wavelength and repetition-rate tunable optical pulse-trains for ultrafast optical time- and wavelength division multiplexing are generated from a semiconductor fiber ring laser by optical injection mode-locking. The pulse trains show the pulse with of ${\sim}10$ ps and the wavelength tuning of wider than 30 nm at various repetition-rates of 10 GHz, 20 GHz, 30 GHz and 40 GHz, respectively.