• Bulletin of the Korean Chemical Society
• /
• 제24권5호
• /
• pp.600-604
• /
• 2003

The light pressure force from an optical standing wave (SW) can focus an atomic beam to submicrometer dimensions. To make the best of this technique it is necessary to find a set of optimal experimental parameters. In this paper we consider theoretically the chromium atoms focusing and demonstrate that the focusing performance depends not only on the strength of but also on the time atoms take to traverse the force field. The general conclusions drawn can easily be applied to other atoms. To analyze the problem we numerically integrate a coupled time-dependent $Schr{\"{o}}dinger$ equation over a wide range of experimental parameters. It is found that an optimal atomic beam speed-laser intensity pair does exist, which could give substantially improved focusing over the one with the experimental parameters given in the literature. It is also shown that the widely used classical particle optics approach can lead to erroneous predictions.

• 한국자기학회지
• /
• 제13권3호
• /
• pp.115-120
• /
• 2003

스퍼터링 방법으로 FM/M/FM의 다층박막을 증착한 다음 초소형 박막 인덕터를 제작하기 위하여 반도체 공정을 대체할 수 있는 레이저 미세가공 기술을 개발하였다. TE $M_{00}$ 모드로 발진하는 CW Nd:YAG 레이저를 active Q-switching 하여 펄스폭이 200 ns인 극 초단 레이저 펄스를 얻었다. 레이저 미세가공 조건을 반복율 5 kHz, 펄스 당 에너지 5 mJ/pulse로 최적화 하여 분해능이 20 $\mu\textrm{m}$인 line patterning을 얻었다.

• 한국광학회지
• /
• 제6권4호
• /
• pp.310-316
• /
• 1995

유한영역에서의 조화함수전개법으로 인접한 두 도파로 코어 중심간의 거리 및 도파로 변수에 따른 결합길이를 계산하여 $1.3/1.55\mum$ WDM coupler을 설계하였다. 저압화학기상증착법에 의해 PSG 도파박막을 제작하고 laser lithography와 $CF_4/O_2$ RIE 공정 등을 이용하여 WDM coupler를 제작하였다. 또한 광섬유를 지지 및 고정하기 위하여 Si 기판 위에 V-groove를 만들었으며 제작된 WDM coupler와 V-groove로 지지된 광섬유를 UV curing epoxy를 사용하여 접속하였다. 제작된 WDM coupler의 $1.3.\mum$, $1.55\mum$에서의 분지별 도파모드를 관측하고 분할비를 측정한 결과 최대 분할비는 각각 9dB, 12dB였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제49권1호
• /
• pp.24-29
• /
• 2000

We propose a simple method to control the crystallization depth of amorphous silicon (a-Si) deposited by PECVD or LPCVD during the excimer laser annealing (ELA). Employing the new method, we have formed poly-Si/a-Si double film and fabricated a new poly-Si TFT with vertical a-Si offsets between the poly-Si channel and the source/drain of TFT without any additional photo-lithography process. The maximum leakage current of the new poly-Si TFT decreased about 80% due to the highly resistive vertical a-Si offsets which reduce the peak electric field in drain depletion region and suppress electron-hole pair generation. In ON state, current flows spreading down through broad a-Si cross-section in the vertical a-Si offsets and the current density in the drain depletion region where large electric field is applied is reduced. The stability of poly-Si TFT has been improved noticeably by suppressing trap state generation in drain region which is caused by high current density and large electric field. For example, ON current of the new TFT decreased only 7% at a stress condition where ON current of conventional TFT decreased 89%.

• 소성∙가공
• /
• 제14권5호
• /
• pp.473-476
• /
• 2005

The demand of on-chip total analyzing system with MEMS (micro electro mechanical system) bio/chemical sensor is rapidly increasing. In on-chip total analyzing system, to detect the bio/chemical products with submicron feature size, a filtration system with nano-filter is required. One of the conventional methods to fabricate nano-filter is to use direct patterning or RIE (reactive ion etching). However, those procedures are very costly and are not suitable fur mass production. In this study, we suggested new fabrication method for a nano-filter based on replication process, which is simple and low cost process. After the Si master was fabricated by laser interference lithography and reactive ion etching process, the polymeric mold was replicated by UV-imprint process. Metallic nano-filter was fabricated after removing the polymeric part of metal deposited polymeric mold. Finally, our fabrication method was applied to metallic nano-filter with $1{\mu}m$ pitch size and $0.4{\mu}m$ hole size for bacteria sensor application.

• 한국전기전자재료학회논문지
• /
• 제23권3호
• /
• pp.245-249
• /
• 2010

Two dimensional(2D) pair-photonic crystals (pair-PCs) have been fabricated by a multiple-exposure nanosphere lithography (MENSL) method using the self-assembled nanospheres as lens-mask patterns and the collimated laser beam as a multiple-exposing source. The arrays of the 2D pair-PCs exhibited variable lattice structures and shape the control of rotating angle (${\Theta}$), tilting angle (${\gamma}$) and the exposure conditions. In addition, the base period or filling factor of pair-PCs as well as their shapes could be changed by experimental conditions and nanosphere size. A 1.18-${\mu}m$-thick resist was spincoated on Si substrate and the multiple exposure was carried out at change of ${\gamma}$ and ${\Theta}$. Images of prepared 2D pair-PCs were observed by SEM. We believe that the MENSL method is a suitable useful tool to realize the pair-periodic arrays of large area.

• 한국광학회지
• /
• 제4권4호
• /
• pp.373-380
• /
• 1993

축소배율(M=+1/5)을 갖는 극자외선(deep ultra-violet) 리소그라피용 5-반사광학계를 설계하였다. 먼저 모든 3차 수차와 5차 구면수차를 영으로 하는 수치적인 해를 구면에 대해서 구하였다. 다음 비교적 크게 나타나는 잔류 수차(구면수차, 코마)의 제거를 위하여 마지막 두 반사경에 대하여 비구면화를 optimization방법에 의해 이행하였다. 이렇게 하여 얻은 광학계는 광원을 KrF 엑시머 레이저(파장 $0.248{\mu}m$)로 하는 nearly incoherent illumination(${\sigma}$=1)인 경우, NA는 0.45, 분해능은 50% MTF 기준치에서 depth of focus $1.0{\mu}m$에 대해 약 500 cycles/mm의 성능을 갖는 시스템이 되었다.

• Current Optics and Photonics
• /
• 제3권5호
• /
• pp.401-407
• /
• 2019

Polymeric optical waveguide devices with Bragg gratings have been investigated, for implementing tunable lasers and wavelength filters used in wavelength-division-multiplexed optical communication systems. Owing to the excellent thermo-optic effect of these polymers, wavelength tuning is possible over a wide range, which is difficult to achieve using other optical materials. In this study the phase-mask technology, which has advantages over the conventional interferometeric method, was introduced to facilitate the fabrication of Bragg gratings in polymeric optical waveguide devices. An optical setup capable of fabricating multiple Bragg gratings simultaneously on a 4-inch silicon wafer was constructed, using a 442-nm laser and phase mask. During fabrication, some of the diffracted light in the phase mask was totally reflected inside the mask, which affected the quality of the Bragg grating adversely, so experiments were conducted to solve this issue. To verify grating uniformity, two types of wavelength-filtering devices were fabricated using the phase-mask lithography, and their reflection and transmission spectra were measured. From the results, we confirmed that the phase-mask method provides good uniformity, and may be applied for mass production of polymer Bragg-grating waveguide devices.

• 한국재료학회지
• /
• 제21권12호
• /
• pp.697-702
• /
• 2011

Two-dimensional (2D) nano patterns including a two-dimensional Bravais lattice were fabricated by laser interference lithography using a two step exposure process. After the first exposure, the substrate itself was rotated by a certain angle, $90^{\circ}$ for a square or rectangular lattice, $75^{\circ}$ for an oblique lattice, and $60^{\circ}$ for a hexagonal lattice, and the $90^{\circ}$ and laser incident angle changed for rectangular and the $45^{\circ}$ and laser incident angle changed for a centered rectangular; we then carried out a second exposure process to form 2D bravais lattices. The band structure of five different 2D nano patterns was simulated by a beam propagation program. The presence of the band-gap effect was shown in an oblique and hexagonal structure. The oblique latticed ZnO nano-photonic crystal array had a pseudo-bandgap at a frequency of 0.337-0.375, 0.575-0.596 and 0.858-0.870. The hexagonal latticed ZnO nano-crystallite array had a pseudo-bandgap at a frequency of 0.335-0.384 and 0.585-0.645. The ZnO nano structure with an oblique and hexagonal structure was grown through the patterned opening window area by a hydrothermal method. The morphology of 2D nano patterns and ZnO nano structures were investigated by atomic force microscopy and scanning electron microscopy. The diameter of the opening window was approximately 250 nm. The height and width of ZnO nano-photonic crystals were 380 nm and 250 nm, respectively.

• 한국정보통신학회논문지
• /
• 제21권6호
• /
• pp.1225-1230
• /
• 2017

3D 프린터는 산업용을 중심으로 성장해 왔으나 최근 경제 효과 및 기술 발달로 인한 원가 절감 등으로 인해 개인용 3D 프린터 시장의 성장이 가속화되는 추세이다. 그러나 현재 보급되고 있는 3D 개인용 프린터는 조형 속도, 크기, 정밀도 등의 한계점에 따라 소비자 만족도가 매우 낮은 편이다. 따라서 본 논문에서는 이러한 개인용 3D 프린터의 기술적 한계를 극복하기 위해 LSU를 이용한 SLA 방식의 3D 프린터를 제안하였다. 그리고 핵심 기능을 담당하는 스캐닝 기구부의 동작을 확인하기 위해 스테핑 모터를 이용한 조형판의 이동 및 레이저 출력 테스트를 시행하였다. 해당 테스트를 통해 레이저 동작 및 제어가 가능한지 확인하였으며 아울러 레이저 모듈과 폴리곤 미러를 사용하여 X축에 일정한 점이 출력됨을 확인하였다. 제안하는 3D프린터는 정밀도와 제조 속도를 개선하여 기존의 보급 형 3D프린터를 대체할 수 있을 것으로 기대한다.