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Terahertz Generation in Quasi-Phase-Matching Structures Using Femtosecond Laser Pulses
유난이,유봉안,정창수,기철식,고도경,박해용,김재은,이종민,이욱재,이영락 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
Terahertz radiation generated by using femtosecond laser pulses was demonstrated in a periodically poled lithium niobate crystal. Two different terahertz radiations, forward and backward, could be obtained in the quasi-phase matching structures due to the difference frequency generation. A broadband femtosecond optical pulse contributes to such a difference frequency generation process, which occurs between an ultrashort laser pulse and a terahertz pulse. We achieved a backward terahertz radiation around 1.3 THz with quasi-phase-matching periods of 30.3, 30.5 and 30.8 $\mu$m by using about 150-fs laser pulses. The terahertz radiations with narrow-bandwidths could be easily controlled by varying the quasi-phase-matching structures.
柳蘭容,宋順子,金鍾順,張壽慶 高麗大學校 倂設 保健大學 保健科學硏究所 1972 保健科學論集 Vol.3 No.1
We are urgently need to improve our dietical living for the health of peoples, improve of one's physical condition and promotion of nations development with strong strength, without behind from compare with the developed countries. The improvement of dietical life is mainly objected for the nutrition improvement of peoples. For the achievement of this goal, the report was not satisfied for the detail research that based only genearal on peoples' nutrition. Therefore, examination should be made on the particular areas for their conditions of take nutriments and compare with general areas and particular areas for the nutrition differences, when the take correction of lacks of nutrition aport ion, it is possible to improve the peoples livehood. The particular areas that I have selected for examination was; Fisher Woman Village, Buk chon-ri, Bukchon-myon, Buk-kun, Chejoo-do, Korea, and general area was selected at Mae-gok-ri, Nam-myon, Yangjoo-kun, Kyunggi-do, Korea, and it's result was evaluated with comparision of two areas in particular general areas. Each area has their particular production crops and their consurntions of large nutriment foods and appetite has been studied. I belief this would be good references of research materials for the improve of dietical living that we urgently needed. Also physical examination was based for the evaluation on the height, weight, girft of head, thickness of skin, etc. but blood, urine, excrement examination was not able to conduct the examination due to the lacks of prepared facilites for the biological examinations.
High Efficiency Optical Phased Array Using Silicon Nitride Waveguide
박병찬,유난이,손성진 한국물리학회 2020 새물리 Vol.70 No.9
A high-efficiency grating antenna and a multimode interference beam splitter using a siliconnitride waveguide have been studied for an optical phased array with an operating wavelength of 1550 nm. A waveguide grating antenna with patterned top cladding and a 1x2 multimode interference beam splitter with a tapered waveguide are considered. The optimized waveguide grating antenna and the multimode interference beam splitter offer above 70% directionality and 98% high single-mode transmission, respectively. These results indicate the possibility of using silicon nitride as a waveguide for a high-efficiency optical phased array.
한해욱,유난이,전태인,진윤식,박익모,김정회,문기원,한연호,정은아,강철,이영락,고도경,이의수,지영빈,김근주,한경호 한국전자파학회 2008 전자파기술 Vol.19 No.5
최근 테라헤르츠 펄스 기술을 근간으로 하는 테라헤르츠 포토닉스 분야는 새로운 연구 주제로서 전세계적으로 큰 관심을 모으고 있다. 단지 순수과학적 측면에서 뿐만 아니라 상업적 응용 가능성이 높아짐에 따라 많은 선진국에서는 테라헤르츠 포토닉스의 발전을 위해 지대한 노력을 경주하고 있다. 저명한 국제 학술지와 국제 학회에서 테라헤르츠 펄스기술에 대한 논문의 수가 폭발적으로 증가하고 있다는 것은 이러한 사실을 뒷받침하고 있다. 테라헤르츠 응용 기술은 테라헤르츠 펄스 광원과 검출기, 그리고 관련된 수동 소자의 개발이 선행되어야 한다. 따라서 본 논문에서는 테라헤르츠 광전도 안테나, 광정류, 준위상 정합 기반 차주파수 발생, 전광 샘플링, 고속 실시간 측정, 테라헤르츠 전송선, 그리고 각종 도파로 구조와 같은 기초적이면서 핵심적인 소자와 측정 기술에 대하여 간략히 기술하고자 한다. In recent years, the field of ㎔ photonics based on ㎔ pulse technology has gained tremendous, worldwide interest as a new exciting research subject. With a possibility of many commercial applications as well as fundamental scientific achievements in the field, many advanced nations are stepping up their effort in advancing the field of ㎔ photonics. This fact is supported by the observation of the significant increase in the number of papers on ㎔ pulse technology presented in renowned international journals and conferences. The subject that is interesting for the ㎔ application is the development of ㎔ pulse sources and detectors, and other passive devices. In this paper, we present a brief review on some of the key devices and their relavant measurement techniques such as ㎔ photoconductive antennas, optical rectificaton, difference frequency geneneration with quasi-phase matching structures, electrooptic sampling, high speed real time measurements, ㎔ transmission lines, and other various waveguide structures.
Group Velocity Matched Second Harmonic Generation in Periodically Poled Potassium Niobate
차명식,유난이,Sunao Kurimura,Kenji Kitamura,Satoshi Ashihara,Takayuki Ohta,Tsutomu Shimura,Kazuo Kuroda,Oc-Teob Jeon 부산대학교 유전체물성연구소 2004 유전체 논문집 Vol.3 No.
We investigated the group velocity matched second harmonic generarion in periodically poled potassium niobate. The QPM wavelength bandwidth was 38 nm around 1520 nm at 35℃ in 14.4㎛ QPM period with 10.5 mm interaction length. We also observed ultra-fast pulse used type-ⅠSHG conversion efficiency. The SHG conversion efficiency of the PPKN crystal was about 3 times that of type-Ⅰ SHG in PPMgLN.
박병찬,유난이 한국광학회 2023 한국광학회지 Vol.34 No.6
The optical signal injected into an end-fire optical phased array (OPA) propagates along the waveguides inside the device and is emitted from the edge of the antenna. In general, reflection and scattering occur at the boundary, thereby reducing the emission efficiency of the optical signal. Inthis article, we propose a silicon nitride (Si 3 N 4 ) tapered waveguide antenna structure whose width is tapered toward the emitting edge that achieveshigh emission efficiency operating at the 1,550 nm wavelength. The Si 3 N 4 tapered waveguide antenna was numerically designed using the 3D finite difference time domain (3D FDTD). The optical signal emission efficiency increased from 78% to 96.3%, while reflectance decreased from 22% to 3.7% compared with the non-tapered waveguide antenna counterpart. This significant outcome will not only have boosted the optical signal intensity but also mitigated optical noise resulting from back reflection along the waveguide in the end-fire optical phased array device.