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RISS 인기검색어
- 검색키워드
- 저자 : Nan Ei Yu (검색결과 21 건)
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Nan Ei YU,Kenji Kitamura,Sunao Kurimura 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.4
A periodically poled device was investigated by using fourth-order quasi-phase-matched (QPM) second harmonic generation (SHG) in MgO-doped stoichiometric lithium tantalate (LiTaO3). The effective nonlinear coefficient was found be 2.4 pm/V by using fourth-order QPM SHG at the fundamental wavelength of 1064 nm. For first-order QPM SHG, the effective value of d33 could be 9.2 pm/V. Using the sensitive higher-order QPM SHG method, we investigated the relationship between the domain duty ratio and the conversion efficiency.
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Terahertz generation in quasi-phase-matching structures
Yu Nan Ei 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.6
Quasi-phase-matching (QPM) technology is considered one of the efcient ways to generate a coherent narrowband terahertz (THz) source. This review addresses two main QPM structures, such as periodically poled nonlinear crystals and optically oriented semiconductors. After briefy introducing the basic principles of QPM structures for THz radiation, we present the device specifcations of the existing narrowband tunable THz source. In the outlook, we discuss the forthcoming prospective materials and domain engineering challenges that must be overcome in the limit of output power and system size on THz source from the viewpoint of a commercially viable lightweight THz system.
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Yu, Nan-Ei,Lee, Yong-Hoon,Lee, Yeung-Lak,Jung, Chang-Soo,Ko, Do-Kyeong,Lee, Jong-Min Optical Society of Korea 2007 Current Optics and Photonics Vol.11 No.4
A high-conversion efficiency, nanosecond pulsed optical parametric generation and amplification with repetition rate of 20 kHz based on a periodically poled MgO-doped stoichiometric lithium tantalate was presented. Pumped by a Q-switched $Nd:YVO_4$ laser at 1064 nm with a pumping power of 4.8W, the generated output power was 1.6W for the signal and idler waves, achieving a slope efficiency of 50%. Using a seed source at signal wave the amplified signal output-pulse energy reached $65{\mu}J$. The obtained maximum gain was 72.4 dB.
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Nan Ei Yu,Changsoo Jung,고도경,Jongmin Lee,Kenji Kitamura,Oleg A Louchev,Sunao Kurimura 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.2I
Thermal dephasing was observed in a periodically poled stoichiometric LiTaO3 crystal during second-harmonic generation at high input power. The dephasing was computationally analyzed using a thermo-optical model consisting of a coupled second harmonic process with absorption and a related temperature distribution. The computational results show a coupled spatio-temporal nanosecond pulse evolution of the fundamental and the second harmonic energy with associated temperature fields, leading to thermal dephasing and inhibition of second-harmonic generation at 1064 nm. The onset of strong non-uniform heat generation and a temperature distribution along the direction of propagation of laser beam take place, depending on the input power, due to linear and nonlinear absorption. A practical temperature adjustment is suggested to compensate the non-uniform thermal distribution and to enhance the conversion efficiency at high input powers.
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Nan Ei Yu,Chul Kang,유형근,Chungsoo Jung,Yeung Lak Lee,Chul-Sik Kee,고도경,Jongmin Lee 한국광학회 2008 Current Optics and Photonics Vol.12 No.3
Coherent tunable terahertz generation was demonstrated in periodically poled stoichiometric lithium tantalate crystal via difference frequency generation of femtosecond laser pulses. Simultaneous forward and backward terahertz radiations were obtained around 1.35 and 0.63 THz, respectively at low temperature. By cooling the crystal to reduce losses caused by phonon absorptions, the generated THz bandwidth was as narrow as 23GHz at the center frequency of 0.63 THz. The measurement result of temperature-dependent showed gradual intensity increase of the generated terahertz pulse and red shift of the center frequency as the temperature decrease from 291 to 143 K, but insignificant reduction of the spectral bandwidth. Furthermore, the stoichiometric crystal was very suitable for the suppression of THz loss at low temperature compared to the congruent LiNbO3 crystal.
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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.
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Highly directional waveguide grating antenna for optical phased array
Han, Kyunghun,Yurlov, Victor,Yu, Nan Ei ELSEVIER 2018 Current Applied Physics Vol.18 No.7
<P>A highly directional waveguide grating antenna by patterning top cladding has been proposed. Spatial separation of the grating structure from the waveguide reduces the strength of perturbation to achieve a millimeter-scale emission. The optimized grating structure offers above 70% directionality with 800 nm waveguide width. The vertical field-of-view of 15 degrees is achieved with 100 nm wavelength bandwidth. Thanks to the its simple structure and large critical dimension, the proposed structure is suitable for manufacturing in CMOS foundries with DUV lithography.</P>
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