• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2009.04a
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• pp.41-48
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• 2009

Laser diode is used as a crucial part for minimization of terrestrial 3D Laser Scanner. But it has certain limitations such as oval beam shape and inevitable astigmatism. In order to realize a parallel light with beam divergence below 1 mrad, These problems of laser diode can be solved through beam shaping by Pinhole and Aperture. Finally, this study could materialize a collimated beam with 0.3 mrad beam divergence angle and 3mm diameter, that performance and checked by using real manufacture.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.244-249
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• 1996

Multipass Ti:sapphire amplifier for the light source of DIAL was developed with an angular-multi-plexing, and the characteristics of output energy and spectra were investigated. As the characteristics of two-stage multipass amplifier, the maximum output energy was 22 mJ and the amplification gain was 20 dB on the wavelength of 790 nm. At that condition, output efficiency of the pumping energy was 18 percent. We obtained $0.15cm^{-1}$ (9.4 pm) as a spectral linewidth in the tuning range of 705~845 nm.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.402.2-402.2
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• 2014

과학과 기술이 발전할수록 나노크기를 넘어서 나노 크기미만의 관찰 분해능과 가공능력이 필수로 요구되어 측정장비와 가공장비의 연구 및 개발이 매우 중요하다. 현재는 주사전자현미경과 투과전자현미경의 발달로 나노크기 이하의 이미징 분해능에는 도달하였지만, 전자 입자의 가벼운 무게 때문에 가공측면에서는 한계를 가지고 있다. 또한 지난 수십 년간 정밀가공에 사용된 갈륨이온 LMIS(Liquid Metal Ion Source)기반의 집속이온빔 시스템은 수십 nm의 가공정밀도를 가지지만 10 nm 미만의 가공정밀도까지 구현하기에는 현재 기술적인 한계로 힘들다. 나노크기 이하의 이미징 분해능과 수 nm의 가공정밀도를 갖는 이온현미경이 최근에 상용화되어 판매되고 있는데, 이 이온 현미경에 사용되는 것이 가스장 이온원(GFIS:Gas Field Ionization Source)이다. 가스장 이온원은 작은 발산각, 작은 가상 이온원 크기 그리고 좁은 에너지 퍼짐의 특징을 가지며 이에 따라 구면수차 및 색수차에도 둔감한 특징을 가지고 있다. 또한 LMIS 는 갈륨이온이 시편속에 파고들어 시편의 물질 특성이 변화되는 문제가 있지만, GFIS에서는 주로 He, Ne 와 같은 불활성 기체를 주로 사용하므로 시편과 반응을 최소화 할 수 있는 장점도 있다. 위와 같은 특징을 갖는 이온빔을 GFIS 로 생성하고 이온현미경에 사용하기 위해서는 이온빔이 팁의 단원자 내지 수 개 정도의 원자에서 생성되도록 해야 한다. 본 연구에서는 GFIS 의 원리를 소개하고 장(전계)이온현미경(Field Ion Microscope)실험을 통하여 GFIS기반으로 생성된 이온빔의 형상을 보여준다. 또한 높은 각전류밀도 구현을 위하여 질소가스 에칭으로 텅스텐 팁 끝 단원자에서만 이온빔을 생성하고, 각전류 밀도 계산과 안정도 실험결과로 본 연구에서 개발한 이온원이 이온총으로서의 이온현미경 적용 가능성에 대해 보여준다.

• Korean Journal of Optics and Photonics
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• v.16 no.2
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• pp.152-158
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• 2005

We investigated the operational characteristics of a Q-switched Nd:YAG laser, which has an unstable resonator with a GRM(Gaussian reflectivity mirror). With electrical input energy of 55 J, we obtained the fundamental energy of 470 mJ at 1064 nm and the frequency doubled energy of 280 mJ at 532 nm. The Top-Hat profile of the output beam was obtained at the near field, and beam divergence was 1.7 mard.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1268-1274
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• 2018

Aircraft-warning lights are lights that are used to inform pilots in flight about the presence of buildings or dangerous objects. Currently, the light sources of most aircraft-warning lights have been replaced by light-emitting diodes (LEDs). However, the aircraft-warning lights that are installed do not meet the optical performance standards and may cause airplane collisions. Therefore, the use of such light poses a risk to aviation safety. In order to solve this problem, we designed a Fresnel lens with the same luminous intensity distribution ovef $360^{\circ}$ direction; thus, we collimated the light beam from the LED light source with a narrow beam divergence angle in the form of an array of aspheric pieces. After that, we designed and simulated an aircraft-warning-light optical system with a center luminous intensity of 20,000 cd and a vertical divergence angle of $3^{\circ}$ or more by optimizing the lens' tilt and the distance between the LED and the Fresnel lens.

• Korean Journal of Optics and Photonics
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• v.15 no.2
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• pp.158-170
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• 2004

Wireless optical communication is expected for high-speed optical communication in the areas of saturated optical fiber communication and low population density. In this paper, we present an optical transmitter system for wireless optical communication with new design concepts different from the usual optical imaging system. The specifications are the following: the source is a laser diode(LD) of wavelength 830 nm in which the divergent angle from the tangential plane differs from that from the sagittal plane. Here, the requested transmission distances are very long range such as 500 m to 1500 m and beam diameter is 3 m at the receiver with symmetrical energy distribution. For the evaluation characteristics of this kind of non-imaging system, two optical quantities, the relative illumination distribution and energy transfer efficiency, are numerically calculated through lots of ray tracing.

• Korean Journal of Optics and Photonics
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• v.6 no.1
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• pp.16-20
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• 1995

We have studied the spectral narrowing characteristics of the tunable Ti:sapphire laser pumped by the second harmonic generation of Nd:YAG laser. Ti:sapphire laser has uniform excitation distribution by both-side end pumping. We have controlled the angle of grating linearly and achieved the continuous selection of wavelength in the broad range from 705 to 835 nm. The output energy of $380{\mu}J$ at 790 nm. the spectral linewidth of $0.13cm_{-1}$ and the beam divergence of 1.2 mrad have been obtained. The wavelength range with power more than 50% of maximum output was 730-825 nm.825 nm.

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.461-465
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• 1994

The spatial flatness of dye jet depending on the Reynold's number has analyzed by using a Michelson interferometer. When the Reynold's number of dye jet was 600, the flatness of the flow was the best. Under this condition, the dye laser with Littman-type configuration has been operated in a single longitudinal mode at the pumping energy of 0.5~1.0 mJ/pulse. The conversion efficiency and beam divergence were 4.7% and 3 mrad, respectively. ively.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.9-12
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• 1991

방전가열형 구리증기레이저의 비축형 불안정공진기를 사용하여 레이저의 빔발산각을 안정공진기의 경우에 비해 25배 (200 $\mu$rad) 까지 줄였다. 이때 불안정공진기의 배율 M 은 50 이었으며, 평균출력은 안정공진기를 사용할 경우에 비해 53 %를 얻었다. 또한, M이 8.5 일 때 (750 $\mu$rad) 평균출력은 안정공진기의 94% 까지 도달하였다.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.204-208
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• 2002

We investigate the dependence of indium tin oxide (ITO) thin films on the mixing ratio of Ar:O$_2$ produced by an ion-gun and $O_2$ injected inside the divergence angle of the ion-beam to optimize their sheet resistance and transmittance. The substrate is placed outside the divergence angle, and the films are grown by ion mixing with ITO evaporated at room temperature. From the XRD measurement ITO films are found to be amorphous. ITO thin films show the highest transmittance of 85% at 3$\times$10$^{-5}$ Torr of 0$_2$ and Ae:O$_2$ ratio of 40:60, and the smallest sheet resistance of 132 $\Omega$/$\square$at 1$\times$10$^{-5}$ Torr of $O_2$ and As:O$_2$ ratio of 40:60.