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533 results on '"Park Q-Han"'

109. Measuring the optical permittivity of two-dimensional materials without a priori knowledge of electronic transitions.

Author

Jung, Gwang-Hun, Yoo, SeokJae, and Park, Q-Han

Subjects
PERMITTIVITY, POLARIZATION (Electrochemistry), TWO-dimensional materials (Nanotechnology)
Abstract

We propose a deterministic method to measure the optical permittivity of two-dimensional (2D) materials without a priori knowledge of the electronic transitions over the spectral window of interest. Using the thin-film approximation, we show that the ratio of reflection coefficients for s and p polarization can give a unique solution to the permittivity of 2D materials within the measured spectral window. The uniqueness and completeness of our permittivity measurement method do not require a priori knowledge of the electronic transitions of a given material. We experimentally demonstrate that the permittivity of monolayers of MoS2, WS2, and WSe2 in the visible frequency range can be accurately obtained by our method. We believe that our method can provide fast and reliable measurement of the optical permittivity of newly discovered 2D materials. [ABSTRACT FROM AUTHOR]

Published
2019
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132. Babinet-Inverted Optical Yagi–Uda Antenna for Unidirectional Radiation to Free Space

Author

Kim, Jineun, Roh, Young-Geun, Cheon, Sangmo, Choe, Jong-Ho, Lee, Jongcheon, Lee, Jaesoong, Jeong, Heejeong, Kim, Un Jeong, Park, Yeonsang, Song, In Yong, Park, Q-Han, Hwang, Sungwoo, Kim, Kinam, Lee, Changwon, Kim, Jineun, Roh, Young-Geun, Cheon, Sangmo, Choe, Jong-Ho, Lee, Jongcheon, Lee, Jaesoong, Jeong, Heejeong, Kim, Un Jeong, Park, Yeonsang, Song, In Yong, Park, Q-Han, Hwang, Sungwoo, Kim, Kinam, and Lee, Changwon

Abstract

Nanophotonics capable of directing radiation or enhancing quantum-emitter transition rates rely on plasmonic nanoantennas. We present here a novel Babinet-inverted magnetic-dipole-fed multislot optical Yagi–Uda antenna that exhibits highly unidirectional radiation to free space, achieved by engineering the relative phase of the interacting surface plasmon polaritons between the slot elements. The unique features of this nanoantenna can be harnessed for realizing energy transfer from one waveguide to another by working as a future “optical via”.

Published
2014

135. Babinet-Inverted Optical Yagi–Uda Antenna for Unidirectional Radiation to Free Space

Author

Kim, Jineun, primary, Roh, Young-Geun, additional, Cheon, Sangmo, additional, Choe, Jong-Ho, additional, Lee, Jongcheon, additional, Lee, Jaesoong, additional, Jeong, Heejeong, additional, Kim, Un Jeong, additional, Park, Yeonsang, additional, Song, In Yong, additional, Park, Q-Han, additional, Hwang, Sung Woo, additional, Kim, Kinam, additional, and Lee, Chang-Won, additional

Published
2014
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140. Metamaterials and chiral sensing: a review of fundamentals and applications

Author

Yoo, SeokJae and Park, Q-Han

Abstract

Chirality, a property of broken mirror symmetry, prevails in nature. Chiral molecules show different biochemical behaviors to their mirror molecules. For left or right circularly polarized lights, the fundamental chiral states of electromagnetic fields interact differently with chiral matter, and this effect has been used as a powerful tool for the detection of chiral molecules. This optical sensing, also termed chiral sensing, is not only easy to implement but also non-invasive to the analytes. However, the measurements made by the optical sensing of chiral molecules are challenging, as chiroptical signals are extremely weak. Recent years have seen active research efforts into metamaterial and plasmonic platforms for manipulating local fields to enhance chiroptical signals. This metamaterial approach offers new possibilities of chiral sensing with high sensitivity. Here, we review the recent advances in chiral sensing using metamaterial and plasmonic platforms. In addition, we explain the underlying principles behind the enhancement of chiroptical signals and highlight practically efficient chiral sensing platforms. We also provide perspectives that shed light on design considerations for chiral sensing metamaterials and discuss the possibility of other types of chiral sensing based on resonant metamaterials.

Published
2018
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141. Measuring the optical permittivity of two-dimensional materials without a prioriknowledge of electronic transitions

Author

Jung, Gwang-Hun, Yoo, SeokJae, and Park, Q-Han

Abstract

We propose a deterministic method to measure the optical permittivity of two-dimensional (2D) materials without a prioriknowledge of the electronic transitions over the spectral window of interest. Using the thin-film approximation, we show that the ratio of reflection coefficients for s and p polarization can give a unique solution to the permittivity of 2D materials within the measured spectral window. The uniqueness and completeness of our permittivity measurement method do not require a prioriknowledge of the electronic transitions of a given material. We experimentally demonstrate that the permittivity of monolayers of MoS2, WS2, and WSe2in the visible frequency range can be accurately obtained by our method. We believe that our method can provide fast and reliable measurement of the optical permittivity of newly discovered 2D materials.

Published
2018
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145. Scattering of Solitons in Derivative Nonlinear Schr��dinger Model

Author

Min, Hyunsoo and Park, Q-Han

Subjects
High Energy Physics - Theory (hep-th), FOS: Physical sciences, Nonlinear Sciences::Pattern Formation and Solitons
Abstract

We show that the chiral soliton model recently introduced by Aglietti et al. can be made integrable by adding an attractive potential with a fixed coefficient. The modified model is equivalent to the derivative nonlinear Schr��dinger model which does not possess parity and Galilean invariance. We obtain explicit one and two classical soliton solutions and show that in the weak coupling limit, they correctly reproduce the bound state energy as well as the time delay of two-body quantum mechanics of the model., 8 pages, Latex

Published
1996
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