• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.37-42
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• 2000

We have numerically solved rate-equations of semiconductor optical amplifier (SOA) to understand the characteristics of SOA. The rate-equations we have used can describe injection carrier density, amplified spontaneous emission and signal photon density in spatial and time domain by dividing the cavity into multi-section. We have investigated injection carrier density, amplified spontaneous emission and signal photon density as a function of position and time in the case of single channel input in the form of square pulse. Also we have analyzed the non-linear phenomena of SOA in the case of injecting multi-channel wavelengths as in WDM. Intermodulation distortion (IMD) caused by beat among channels has significant effects on the signal distortion as the channel spacing becomes narrower, and channel crosstalk becomes larger as the power of signals increases. In the case of the injection of another CW laser whose wavelength is far enough from the signal wavelengths, the crosstalk and the output signal distortion can be significantly reduced. duced.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.273-277
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• 2006

In this paper, we constructed the Littman type and fixed Littrow type tunable external-cavity diode laser systems. The laser output, which is the 0th-order diffracted beam from the diffraction grating in an external cavity, was the single longitudinal mode. Its FWHM was measured as less than 9MHz. With the diode driving current of 140mA and operating temperature of $25^{\circ}C$, the coarse tuning range of 5.375nm was measured for the Littman type, and of 13.65nm was measured for the fixed Littrow type. 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 0.042nm was measured for both types. The fixed Littrow type tunable external-cavity diode laser system was an improvement on the conventional Littrow type tunable laser system in which the output direction varies due to the grating embedded in the mirror plate.

• Korean Journal of Optics and Photonics
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• v.33 no.1
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• pp.22-27
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• 2022

We fabricate a polarization-independent dielectric multilayer thin-film diffraction grating for a spectral-beam-combining (SBC) system with a simple grating structure and low aspect ratio. Due to the refractive index and thickness error of the manufactured thin films, the diffraction efficiency of the fabricated diffraction grating was lower than that of the design. The causes of the errors were analyzed, and it was confirmed through simulation that diffraction efficiency could be compensated through an additional coating on the manufactured diffraction grating. As a result of sputtering an additional Ta₂O₅ layer on a fabricated diffraction grating, the diffraction efficiency was corrected and a maximum 91.7% of polarization-independent diffraction efficiency was obtained.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.123-124
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• 2011

반도체 기술의 비약적 발전에 힘입어 현재의 개인용 컴퓨터는 고성능 CPU를 탑재하고 1990대의 텍스트 기반의 운영체제에서 벗어나 그래픽 기반의 운영체제에서 다양한 멀티미디어 기능을 제공 한다. 이를 위한 입력장치로 텍스트 기반 운영체제에서 주로 사용된 키보드뿐 아니라 마우스, 카메라, 터치스크린 등의 다양한 장치들이 사용되고 있다. 그러나 빔 프로젝터를 이용한 프레젠테이션의 경우 아직도 레이저포인터를 이용한 발표가 일반적이며 발표자와 빔 프로젝트용 PC와의 인터랙션이 없기 때문에 다양한 멀티미디어 기능 구현이 제한적이다. 본 논문에서는 USB 웹 카메라를 이용하여 프로젝터 화면을 촬영한 후 영상처리 라이브러리인 OpenCV를 기반으로 레이저 포인터의 위치와 동작을 검출하여 원거리에서도 사용자가 레이저 포인터를 이용하여 마우스 동작을 재현할 수 있는 시스템을 개발하고자 한다. 이를 활용하면 레이저 포인터를 사용하여 발표자가 별도의 입력장치 없이 PC와의 인터랙션이 가능해져서 다양한 멀티미디어 기반의 프레젠테이션이 가능해진다.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.370-374
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• 1996

A Superstructure Grating(SSG) Distributed-Bragg-Reflector(DBR) laser has a broad tuning range with a good mode suppression ratio. However, gaps of channel are observed in the wavelength-tuning characteristics of an SSGDBR laser which employs linearly-chirped DBR mirrors. We found by numerical simulation that the gaps may be attributed to the nonuniform reflection-peak heights of a linearly-chirped DBR mirrors. We propose a nonlinearly chirped grating DBR mirror structure that makes reflection-peak heights almost uniform. Therefore a nonlinearly chirped grating structure can be employed in an extended tuning range semiconductor laser to achieve gap-free tuning and low threshold current operation simultaneously.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.317-327
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• 2018

Terahertz (THz) time-domain spectroscopy(TDS), imaging techniques, and related systems have become mature technologies, widely used in many universities and research laboratories. However, the development of creative technologies still requires improved THz application systems. A few key points are discussed, including the innovative advances of mode-locking energy-emitting semiconductor lasers and better photoconductive semiconductor quantum structures. To realize a compact, low cost, and high performance THz system, it is essential that THz spectroscopy and imaging technologies are better characterized by semiconductor and nano-devices, both static and time-resolved. We introduce the THz spectroscopy and imaging systems, the OSCAT(Optical Sampling by laser CAvity Tuning) system and the ASOPS(ASynchronous Optical Sampling) system, are constructed by our research team. We report on the THz images obtained from their use.

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.482-486
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• 1999

Ultrafast carrier dynamics of LT-GaAs semiconductors was investigated by using time-resolved photoreflectance spectroscopy. We can see that decay dynamics of photoreflectance generated by carriers depends strongly on the excitation wavelength due to the structure distortion of LT-GaAs semiconductors. Ultrafast trapping of excited carriers into deep trap states gives rise to transient photoreflectance decays with a lifetime shorter than 1 ps. Also, the long-lived photoreflectance is attributed to the carriers trapped deeply at point defects. fects.

• Electrical & Electronic Materials
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• v.17 no.5
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• pp.30-36
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• 2004

현대 사회는 지식 정보화를 추구하며 변화하고 있다. 지식, 정보화 사회는 개인, 기업 및 사회 모든 주체의 업무효과의 극대화할 수 있는 인프라를 제공하게 될 것이며 이는 영상, 음성, 데이터 등의 다양한 정보의 교환으로 이어져 인간생활의 새로운 혁신을 예고하고 있다. 한편 지식 정보화에는 고도의 정보 저장 및 통신기술이 필수적으로 요구되며 기존의 실리콘기반 소자의 고성능화 이외에 새로운 기술혁신을 요구하고 있다. 1980년대 이후 광통신에 레이저가 응용되고 1990년대 후반에 이르러 수십 나노미터 크기의 양자우물 구조의 화합물 반도체기반의 녹색 및 청색 LD, LED 및 백색 광 다이오드가 구현되면서 화합물 반도체는 정보 통신에 적합한 소재로 인식되기 시작하였다. 기존 실리콘과 다른 물리적 화학적 성질로 인하여 적극적인 연구와 기술적인 시도가 이루어지고 있다. 1900년대 실리콘기반 전자 소자 기술이 비약적으로 발전하면서 새로운 혁신을 보여주었고 그 포화된 기술에 뒤를 이어 화합물 반도체에 의한 기술의 혁신이 예고 되고 있는 것이다.(중략)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.127-128
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.673-674
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• 2012