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46 results on '"Lee, Chulwon"'

1. Topologically Protected Exceptional Points and Reentrant $\mathcal{PT}$ Phase in an Exact Ternary Model

Author

Lee, Chulwon, Zhang, Kai, Miao, Jinyan, Sun, Kai, and Deng, Hui

Subjects
Physics - Optics, Quantum Physics
Abstract

In open, driven systems where parity-time symmetry is preserved, phenomena that defy conventional wisdom emerge near exceptional points, promising advances in photonics. While most studies focus on two-level systems of a conventional exceptional point, unconventional exceptional points as well as reentrant phases have been discovered in separate studies of higher-dimensional phase spaces. In this Letter, we present a minimal, analytical model that encompasses several key phenomena in higher-dimensional phase spaces, including reentrant PT phases, higher-order exceptional points, and anisotropic exceptional points. Using the exact analytical solution, we identify a new topological index as the unifying origin of these different phenomena. The simplicity of the model may furthermore facilitate experimental implementations for enhanced sensing and efficient polariton devices., Comment: 12 pages, 7 figures

Published
2023

2. 1D photonic crystal direct bandgap GeSn-on-insulator laser

Author

Joo, Hyo-Jun, Kim, Youngmin, Burt, Daniel, Jung, Yongduck, Zhang, Lin, Chen, Melvina, Parluhutan, Samuel Jior, Kang, Dong-Ho, Lee, Chulwon, Assali, Simone, Ikonic, Zoran, Moutanabbir, Oussama, Cho, Yong-Hoon, Tan, Chuan Seng, and Nam, Donguk

Subjects
Physics - Optics, Physics - Applied Physics
Abstract

GeSn alloys have been regarded as a potential lasing material for a complementary metal-oxide-semiconductor (CMOS)-compatible light source. Despite their remarkable progress, all GeSn lasers reported to date have large device footprints and active areas, which prevent the realization of densely integrated on-chip lasers operating at low power consumption. Here, we present a 1D photonic crystal (PC) nanobeam with a very small device footprint of 7 ${\mu}m^2$ and a compact active area of ~1.2 ${\mu}m^2$ on a high-quality GeSn-on-insulator (GeSnOI) substrate. We also report that the improved directness in our strain-free nanobeam lasers leads to a lower threshold density and a higher operating temperature compared to the compressive strained counterparts. The threshold density of the strain-free nanobeam laser is ~18.2 kW cm$^{ -2}$ at 4 K, which is significantly lower than that of the unreleased nanobeam laser (~38.4 kW cm$^{ -2}$ at 4 K). Lasing in the strain-free nanobeam device persists up to 90 K, whereas the unreleased nanobeam shows a quenching of the lasing at a temperature of 70 K. Our demonstration offers a new avenue towards developing practical group-IV light sources with high-density integration and low power consumption., Comment: 14 pages, 6 figures

Published
2021
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5. Polariton-driven $\mathcal{PT}$ Reentry and Anisotropic Exceptional Points in $\mathcal{PT}$-symmetric Ternary System

Author

Lee, Chulwon, Zhang, Kai, Miao, Jinyan, Sun, Kai, and Deng, Hui

Subjects
Quantum Physics, FOS: Physical sciences, Quantum Physics (quant-ph), Optics (physics.optics), Physics - Optics
Abstract

Multi-mode parity-time symmetric non-Hermitian systems feature rich phenomena that promise better photonic technologies, but they are often difficult to understand and implement. Here we show that a three-mode polaritonic system forms a minimal model with reentrant parity-time exact phase. The analytical solution of its phase diagram indicates the reentrant phase is accompanied by several special features of multi-mode systems, including higher-order and anisotropic exceptional points, and near-zero-gain parity-time broken phase. Exciton coupling further facilitates tuning of the system to access the special features for enhanced sensing and efficient polariton devices., 10 pages, 5 figures

Published
2023

8. All‐Around HfO2 Stressor for Tensile Strain in GeSn‐on‐Insulator Nanobeam Lasers.

Author

Joo, Hyo‐Jun, Kim, Youngmin, Chen, Melvina, Burt, Daniel, Zhang, Lin, Son, Bongkwon, Luo, Manlin, Ikonic, Zoran, Lee, Chulwon, Cho, Yong‐Hoon, Tan, Chuan Seng, and Nam, Donguk

Subjects
SOLID-state lasers, ATOMIC layer deposition, LASERS, PHOTONIC crystals, ACTIVE medium, PHOTONICS
Abstract

Tensile strained GeSn alloys are considered a key enabler for the realization of complementary metal‐oxide‐semiconductor laser sources. However, the tensile strained GeSn lasers reported to date require complex fabrication processes for applying tensile strain in GeSn, preventing tensile GeSn lasers from becoming the mainstream technology for integrated photonics. Here, a unique strain engineering method is presented that can introduce a uniform tensile strain in GeSn lasers by harnessing a widely developed atomic layer deposition (ALD) process. 1D photonic crystal nanobeam lasers under homogenous tensile strain induced by an ALD HfO2 all‐around stressor layer show a single‐mode lasing peak with a ≈31 nm redshift and ≈2 times intensity increase. The lasing threshold of tensile strained GeSn lasers is ≈12% improved compared to the unstrained GeSn lasers. It is believed that the approach offers a new path toward the realization of practical group‐IV laser sources for photonic‐integrated circuits. [ABSTRACT FROM AUTHOR]

Published
2023
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10. (Digital Presentation) Gesnoi Laser Technology for Photonic-Integrated Circuits

Author

Joo, Hyo-Jun, primary, Kim, Youngmin, additional, Burt, Daniel, additional, Jung, Yongduck, additional, Zhang, Lin, additional, Chen, Melvina, additional, Luo, Manlin, additional, Parluhutan, Samuel Jior, additional, Kang, Dong-Ho, additional, Lee, Chulwon, additional, Assali, Simone, additional, Son, Bongkwon, additional, Ikonic, Zoran, additional, Moutanabbir, Oussama, additional, Cho, Yong-Hoon, additional, Tan, Chuan Seng, additional, Huang, Yi-Chiau, additional, and Nam, Donguk, additional

Published
2022
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12. GeSn Laser Technologies for Integrated Photonics

Author

Shi, Xuncheng, primary, Burt, Daniel, additional, Kim, Youngmin, additional, Joo, Hyo-Jun, additional, Tan, James, additional, Chen, Melvina, additional, Jung, Yongduck, additional, Zhang, Lin, additional, Tan, Chuan Seng, additional, Lee, Chulwon, additional, Cho, Yong-Hoon, additional, Ikonic, Zoran, additional, Huang, Yi-Chiau, additional, Assali, Simone, additional, Moutanabbir, Oussama, additional, and Nam, Donguk, additional

Published
2022
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13. 1D photonic crystal GeSn-on-insulator nanobeam laser

Author

Joo, Hyo-Jun, primary, Kim, Youngmin, additional, Burt, Daniel, additional, Jung, Yongduck, additional, Zhang, Lin, additional, Chen, Melvina, additional, Parluhutan, Samuel J., additional, Kang, Dong-Ho, additional, Lee, Chulwon, additional, Assali, Simone, additional, Ikonic, Zoran, additional, Moutanabbir, Oussama, additional, Cho, Yong-Hoon, additional, Tan, Chuan Seng, additional, and Nam, Donguk, additional

Published
2022
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17. 1D photonic crystal direct bandgap GeSn-on-insulator laser

Author

Joo, Hyo-Jun, primary, Kim, Youngmin, additional, Burt, Daniel, additional, Jung, Yongduck, additional, Zhang, Lin, additional, Chen, Melvina, additional, Parluhutan, Samuel Jior, additional, Kang, Dong-Ho, additional, Lee, Chulwon, additional, Assali, Simone, additional, Ikonic, Zoran, additional, Moutanabbir, Oussama, additional, Cho, Yong-Hoon, additional, Tan, Chuan Seng, additional, and Nam, Donguk, additional

Published
2021
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25. A broadband ultraviolet light source using GaN quantum dots formed on hexagonal truncated pyramid structures

Author

Cho, Jong-Hoi, primary, Lim, Seung-Hyuk, additional, Jang, Min-Ho, additional, Lee, Chulwon, additional, Yeo, Hwan-Seop, additional, Sim, Young Chul, additional, Kim, Je-Hyung, additional, Matta, Samuel, additional, Alloing, Blandine, additional, Leroux, Mathieu, additional, Park, Seoung-Hwan, additional, Brault, Julien, additional, and Cho, Yong-Hoon, additional

Published
2020
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29. 1D photonic crystal GeSn-on-insulator nanobeam laser

Author

Reed, Graham T., Knights, Andrew P., Joo, Hyo-Jun, Kim, Youngmin, Burt, Daniel, Jung, Yongduck, Zhang, Lin, Chen, Melvina, Parluhutan, Samuel Jior, Kang, Dong-Ho, Lee, Chulwon, Assali, Simone, Ikonic, Zoran, Moutanabbir, Oussama, Cho, Yong-Hoon, Tan, Chuan Seng, and Nam, Donguk

Published
2022
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30. Strategies for linking vertical cooperative R&D to commercialization in Korea

Author

Lee, Chulwon, Bae, Zong-Tae, and Lee, Jinjoo

Subjects
Industrial research -- Analysis, Technology transfer -- Analysis, Business, Business, general
Abstract

Technology sourcing at the project level is used to determine the utility of vertical cooperative research and development (R&D) strategies employed by various groups of industries in South Korea. Data derived from the relative usage rates of cooperative R&D and of other supplementary technology acquisition methods were subjected to cluster analysis. Results show that other supplementary technology acquisition methods must be used by cooperative R&D projects to obtain commercial applicability.

Published
1994

38. Design and Implementation of the MaxStream Federated Stream Processing Architecture

Author

Botan, Irina, Cho, Younggoo, Derakhshan, Roozbeh, Dindar, Nihal, Haas, Laura M., Kim, Kihong, Lee, Chulwon, Mundada, Girish, Shan, Ming-Chien, Tatbul, Nesime, Yan, Ying, Yun, Beomjin, and Zhang, Jin

Subjects
PROZESSORARCHITEKTUREN + RECHNERARCHITEKTUREN (COMPUTERSYSTEME), MIKROPROZESSOREN + MIKROCOMPUTER (HARDWARE), PROCESSOR ARCHITECTURES + COMPUTER ARCHITECTURES (COMPUTER SYSTEMS), SAP SD Benchmark, Linear Road Benchmark, MICROPROCESSORS + MICROCOMPUTERS (HARDWARE), Data stream processing, SAP MaxDB, Heterogeneity, federated database systems, Data processing, computer science, ddc:004
Abstract

Despite the availability of several commercial data stream processing engines (SPEs), it remains hard to develop and maintain streaming applications. A major difficulty is the lack of standards, and the wide (and changing) variety of application requirements. Consequently, existing SPEs vary widely in data and query models, APIs, functionality, and optimization capabilities. This has led to some organizations using multiple SPEs, based on their application needs. Furthermore, management of stored data and streaming data are still mostly separate concerns, although applications increasingly require integrated access to both. In the MaxStream project, our goal is to design and build a federated stream processing architecture that seamlessly integrates multiple autonomous and heterogeneous SPEs with traditional databases, and hence facilitates the incorporation of new functionality and requirements. In this paper, we describe the design and implementation of the MaxStream architecture, and demonstrate its feasibility and performance on two benchmarks: the Linear Road Stream Data Management Benchmark and the SAP Sales and Distribution Benchmark., Technical Report / ETH Zurich, Department of Computer Science, 632

Published
2009

40. SAP HANA distributed in-memory database system: Transaction, session, and metadata management

Author

Lehner, Wolfgang, Kwon, Yong Sik, Lee, Juchang, Färber, Franz, Muehle, Michael, Lee, Chulwon, Bensberg, Christian, Lee, Joo Yeon, Lee, Arthur H., Lehner, Wolfgang, Kwon, Yong Sik, Lee, Juchang, Färber, Franz, Muehle, Michael, Lee, Chulwon, Bensberg, Christian, Lee, Joo Yeon, and Lee, Arthur H.

Abstract

One of the core principles of the SAP HANA database system is the comprehensive support of distributed query facility. Supporting scale-out scenarios was one of the major design principles of the system from the very beginning. Within this paper, we first give an overview of the overall functionality with respect to data allocation, metadata caching and query routing. We then dive into some level of detail for specific topics and explain features and methods not common in traditional disk-based database systems. In summary, the paper provides a comprehensive overview of distributed query processing in SAP HANA database to achieve scalability to handle large databases and heterogeneous types of workloads.

Published
2013

42. A demonstration of the MaxStream federated stream processing system

Author

Botan, Irina, primary, Cho, Younggoo, additional, Derakhshan, Roozbeh, additional, Dindar, Nihal, additional, Gupta, Ankush, additional, Haas, Laura, additional, Kim, Kihong, additional, Lee, Chulwon, additional, Mundada, Girish, additional, Shan, Ming-Chien, additional, Tatbul, Nesime, additional, Yan, Ying, additional, Yun, Beomjin, additional, and Zhang, Jin, additional

Published
2010
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45. “I Felt Warm, Familiar and Comfortable”: A Case Study of Western Exchange Students Seek Nostalgic Leisure Experiences in South Korea.

Author

Sun, Wanting, Kim, Jasmyn, Park, Jiyoon, and Lee, Chulwon

Subjects
*ACCULTURATION, *STUDENT exchange programs, *EXCHANGE of persons programs, *JUDGMENT sampling, *NOSTALGIA, SNOWBALL sampling
Abstract

AbstractWith the internationalization of Korean culture, choosing South Korea for exchange programs has become a trend among Western students. In exchange programs where Western students adapt to Eastern societies, individuals often encounter various leisure constraints. Leisure nostalgia seems to serve as an emotional support, helping them cope with these leisure constraints. This study utilized purposive snowball sampling to conduct in-depth interviews with eight Western exchange students who experienced leisure constraints in South Korea. It explores how these students use nostalgic leisure experience to overcome limitations in participating in leisure activities in South Korea. The analysis indicates that nostalgic leisure experiences may help Western exchange students escape acculturative stress, establish social connections, and enhance psychological comfort. The study suggests that leisure nostalgia as emotional support may be a strategy for Western exchange students to overcome leisure constraints and promote their leisure participation in South Korea. [ABSTRACT FROM AUTHOR]

Published
2025
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46. Trends and Perspectives of PRC's Energy Policy Making Institutions and Policies*

Author

Lee, Chulwon

Abstract

The future direction of China's approach to energy policy making is, of course, difficult to predict. This is due not only to the opaque and fragmented nature of Chinese energy policy decision-making, but also to the fact that energy policy is a new topic for China's leaders and the individuals they rely on for advice to master that impinges on the interests of actors throughout the Chinese bureaucracy. The wide range of participants in the energy policy debate indicates that more diversified views on it probably reach the top leadership. The impact of the multiplicity of opinions is two-fold. It can result in more informed decision-making, but it can also delay the process as decision makers must assess a larger number of competing and sometimes contradictory views.

Published
2009
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