1,722,681 research outputs found
CHANG JUN YOON
No full text학위논문(석사)--아주대학교 일반대학원 :분자과학기술학과,2006. 2Recent advances in the generation and amplification of ultrashort laser pulses are remarkable due to broad applications in many areas such as ultrafast spectroscopy, imaging and material processing. Recently, optical parametric chirped pulse amplification (OPCPA) turned out to be an efficient method to amplify ultrashort pulses. Using this technique, energies of intensive ns or sub-nanosecond (sub-ns) pump pulses can be efficiently transferred to the spatially and temporally synchronized stretched low-energy seed pulses in a suitable nonlinear crystal. OPCPA is a promising alternative to widely used regenerative and multi-pass amplifiers. It offers some advantages such as extremely broad gain bandwidth, high contrast ratio, low thermal effect, low nonlinear wavefront distortion and compact experimental performance without electro-optic modulators.
Looking at the recent progress in OPCPA, it was divided in two directions. The first trend was concentrated on the development of exceptionally high peak power (TW-level) laser systems at low repetition rates between single short to 10 Hz. Such high-energy OPCPA’s were seeded by pulses from Ti:sapphire laser at the degenerate point near 1 m. The second tendency was related to the development of more compact and stable fs OPCPA systems operating in kHz repetition rates with intermediate powers as alternative of regenerative and multi-pass amplifiers.
In this work, we report on experimental design and characteristics of a Cr:forsterite based OPCPA, what we believe to be the first demonstration in kHz repetition rates. Recently, a complex multi-cascade broadband Cr:forsterite OPCPA was demonstrated with slightly different pump and seed wavelengths to generate J-energies, but at a low repetition rate of 2 Hz. In this work, a kHz diode-pumped frequency-doubled Nd:YVO4 laser was used as pump laser delivering the shortest ns pulses (≤10 ns), up to now. Suitable gain medium was carefully selected by performing theoretical analysis of phase matching properties of different nonlinear crystals such as DKDP, KDP and BBO. Both collinear and noncollinear phase matching geometries were considered and characterized for broadband parametric process. The bandwidth broadening is a prior condition for generation of ultrashort pulses. It turned out that DKDP seems to be the best candidate for Cr:forsterite based OPCPA. Subsequently, first experiment results of the non-degenerate single-pass OPCPA delivering pulses near 935 nm and 1235 nm, respectively, were presented and discussed.목 차
국문요약 ⅰ
그림차례 ⅴ
표 차 례 ⅷ
1. 서론 1
1.1 역사 1
1.2 고출력 극초단 펄스 응용 3
1.3 광매개 처프 펄스 증폭법 5
1.4 연구 목적 8
2. 기본 이론 10
2.1 펄스압축기와 펄스늘임기 10
2.1.1 GVD(Group Velocity Dispersion) 11
2.1.2 프리즘 쌍 13
2.1.3 회절격자 쌍을 이용한 펄스압축기 16
2.1.4 회절격자 쌍을 이용한 펄스늘임기 19
2.2 광매개 이득 22
2.2.1 Noncollinear 위상정합 23
2.2.2 광매개 이득 25
2.2.3 군속도 부정합 26
3. 광매개 처프 펄스 증폭기 제작 28
3.1 공진기 특성 29
3.2 펄스늘임기와 펄스압축기 제작 32
3.2.1 펄스늘임기 수차분석을 위한 광경로 추적 32
3.2.2 펄스늘임기 37
3.2.3 펄스압축기 43
3.3 광매개 증폭기 구성 47
3.3.1 시간적 동기화 실현 47
3.3.2 비선형 단결정의 증폭 가능성 분석 50
3.3.3 DKDP를 이용한 증폭실험 61
4. 결론 및 향후 연구 방향 64
참고문헌 66
Abstract 71Maste
Check-list of Anteoninae R. Perkins, 1912 (Hymenoptera: Dryinidae) of South Korea, with description of a new species
No full textKim, Chang-Jun, Lee, Jong-Wook (2014): Check-list of Anteoninae R. Perkins, 1912 (Hymenoptera: Dryinidae) of South Korea, with description of a new species. Zootaxa 3802 (2): 173-192, DOI: 10.11646/zootaxa.3802.2.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Maximum capacity improvement achievable by using multi-level modulation formats in MCF transmission systems (invited paper)
No full textRobust and Reliable Control for Linear Systems with Parameter Uncertainty and actuator Failure
No full textFemtosecond mode-locked erbium-doped fiber ring laser with intra-cavity loss controlled full L-band wavelength tunability
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
FIGURES 15–19 in Check-list of Anteoninae R. Perkins, 1912 (Hymenoptera: Dryinidae) of South Korea, with description of a new species
No full textFIGURES 15–19. Anteon worakense sp. nov., male. 15. Lateral habitus; 16. Head in frontal view. 17. Scutum; 18. Head in dorsal view; 19. Propodeum. Scale bars: 0.5 mm for 15; 0.2 mm for 16, 17, 18, 19.Published as part of Kim, Chang-Jun & Lee, Jong-Wook, 2014, Check-list of Anteoninae R. Perkins, 1912 (Hymenoptera: Dryinidae) of South Korea, with description of a new species, pp. 173-192 in Zootaxa 3802 (2) on page 186, DOI: 10.11646/zootaxa.3802.2.2, http://zenodo.org/record/22890
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