Search

Your search keyword '"Chou, Yu‐Hsun"' showing total 99 results
Start Over Author "Chou, Yu‐Hsun"
99 results on '"Chou, Yu‐Hsun"'

1. Cavity Floquet engineering

Author

Zhou, Lingxiao, Liu, Bin, Liu, Yuze, Lu, Yang, Li, Qiuyang, Xie, Xin, Lydick, Nathanial, Hao, Ruofan, Liu, Chenxi, Watanabe, Kenji, Taniguchi, Takashi, Chou, Yu-Hsun, Forrest, Stephen R., and Deng, Hui

Published
2024
Full Text
View/download PDF

2. Van der Waals Heterostructure Polaritons with moir\'e-Induced Nonlinearity

Author

Zhang, Long, Wu, Fengcheng, Hou, Shaocong, Zhang, Zhe, Chou, Yu-Hsun, Watanabe, Kenji, Taniguchi, Takashi, Forrest, Stephen R., and Deng, Hui

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Controlling matter-light interactions with cavities is of fundamental importance in modern science and technology. It is exemplified in the strong-coupling regime, where matter-light hybrid modes form, with properties controllable via the photon component on the optical-wavelength scale. In contrast, matter excitations on the nanometer scale are harder to access. In two-dimensional van der Waals heterostructures, a tunable moir\'e lattice potential for electronic excitations may form, enabling correlated electron gases in lattice potentials. Excitons confined in moir\'e lattices have also been reported, but cooperative effects have been elusive and interactions with light have remained perturbative. Here, integrating MoSe$_{2}$-WS$_{2}$ heterobilayers in a microcavity, we establish cooperative coupling between moir\'e-lattice excitons and microcavity photons up to liquid-nitrogen temperature, thereby integrating into one platform versatile control over both matter and light. The density dependence of the moir\'e polaritons reveals strong nonlinearity due to exciton blockade, suppressed exciton energy shift, and suppressed excitation-induced dephasing, all of which are consistent with the quantum-confined nature of the moir\'e excitons. Such a moir\'e polariton system combines strong nonlinearity and microscopic-scale tuning of matter excitations with the power of cavity engineering and long range coherence of light, providing a new platform for collective phenomena from tunable arrays of quantum emitters.

Published
2021
Full Text
View/download PDF

3. Perfect absorption by an atomically thin crystal

Author

Horng, Jason, Martin, Eric W., Chou, Yu-Hsun, Courtade, Emmanuel, Chang, Tsu-chi, Hsu, Chu-Yuan, Wentzel, Michael-Henr, Ruth, Hanna G., Lu, Tien-chang, Cundiff, Steven T., Wang, Feng, and Deng, Hui

Subjects
Condensed Matter - Materials Science, Physics - Optics
Abstract

Optical absorption is one of fundamental light-matter interactions. In most materials, optical absorption is a weak perturbation to the light. In this regime, absorption and emission are irreversible, incoherent processes due to strong damping. Excitons in monolayer transition metal dichalcogenides, however, interact strongly with light, leading to optical absorption in the non-perturbative regime where coherent re-emission of the light has to be considered. Between the incoherent and coherent limits, we show that a robust critical coupling condition exists, leading to perfect optical absorption. Up to 99.6% absorption is measured in a sub-nanometer thick MoSe2 monolayer placed in front of a mirror. The perfect absorption is controlled by tuning the exciton-phonon, exciton-exciton, and exciton-photon interactions by temperature, pulsed laser excitation, and a movable mirror, respectively. Our work suggests unprecedented opportunities for engineering exciton-light interactions using two-dimensional atomically thin crystals, enabling novel photonic applications including ultrafast light modulators and sensitive optical sensing.

Published
2019
Full Text
View/download PDF

4. Engineering Effects of Vacuum Fluctuations on Two-dimensional Semiconductors

Author

Horng, Jason, Chou, Yu-Hsun, Chang, Tsu-chi, Hsu, Chu-Yuan, Lu, Tien-chang, and Deng, Hui

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The resonance energy and the transition rate of atoms, molecules and solids were understood as their intrinsic properties in classical electromagnetism. With the development of quantum electrodynamics, it is realized that these quantities are linked to the coupling of the transition dipole and the quantum vacuum. Such effects can be greatly amplified in macroscopic many-body systems from virtual photon exchange between dipoles, but are often masked by inhomogeneity and pure dephasing, especially in solids. Here, we observe an exceptionally large renormalization of exciton resonance and radiative decay rate in transition metal dichalcogenides monolayers due to interactions with the vacuum in both absorption and emission spectroscopy. Tuning the vacuum energy density near the monolayer, we demonstrate control of cooperative Lamb shift, radiative decay, and valley polarization as well as control of the charged exciton emission. Our work establishes a simple and robust experimental system for vacuum engineering of cooperative matter-light interactions., Comment: 13 pages, 4 figures

Published
2019
Full Text
View/download PDF

5. Highly Valley-Polarized Singlet and Triplet Interlayer Excitons in van der Waals Heterostructure

Author

Zhang, Long, Gogna, Rahul, Burg, G. William, Horng, Jason, Paik, Eunice, Chou, Yu-Hsun, Kim, Kyounghwan, Tutuc, Emanuel, and Deng, Hui

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Two-dimensional semiconductors feature valleytronics phenomena due to locking of the spin and momentum valley of the electrons. However, the valley polarization is intrinsically limited in monolayer crystals by the fast intervalley electron-hole exchange. Hetero-bilayer crystals have been shown to have a longer exciton lifetime and valley depolarization time. But the reported valley polarization was low; the valley selection rules and mechanisms of valley depolarization remains controversial. Here, we report singlet and brightened triplet interlayer excitons both with over 80% valley polarizations, cross- and co-polarized with the pump laser, respectively. This is achieved in WSe2/MoSe2 hetero-bilayers with precise momentum valley alignment and narrow emission linewidth. The high valley polarizations allow us to identify the band minima in a hetero-structure and con_rm unambiguously the direct band-gap exciton transition, ultrafast charge separation, strongly suppressed valley depolarization. Our results pave the way for using semiconductor heterobilayers to control valley selection rules for valleytronic applications.

Published
2019
Full Text
View/download PDF

6. Advancing semantic segmentation of two-dimensional materials using a semantic-adaptive transformer model.

Author

Cheung, Wing-Sing, You, Min-Hsuan, Syu, Si-Yao, Chou, Yu-Hsun, and Chen, Chi-Yeh

Subjects
CHEMICAL vapor deposition, PHOTOLUMINESCENCE, PRIOR learning, MONOMOLECULAR films, SPECTROMETRY
Abstract

Accurate detection and characterization of two-dimensional (2D) materials are essential for their effective utilization in various applications. Traditional techniques, such as chemical vapor deposition, often produce materials with high defect density, while mechanical exfoliation is hindered by its labor-intensive and time-consuming nature. In this Letter, we propose a semantic-adaptive transformer model, termed Semptive, designed specifically for the precise detection of monolayer MoS2. Our approach integrates a semantic adaptation module with a multi-head self-attention mechanism, incorporating deep supervision and leveraging prior knowledge to enhance model performance. The model was trained on a dataset obtained through mechanical exfoliation and validated using photoluminescence spectroscopy. The experimental results reveal that Semptive significantly enhances segmentation performance compared to conventional models, achieving higher Intersection over Union and Dice scores while reducing computational demands. This method represents a notable advancement in the efficient and precise identification of 2D materials, providing substantial improvements for material characterization and device fabrication processes. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

7. Single-crystalline aluminum film for ultraviolet plasmonic nanolasers

Author

Chou, Bo-Tsun, Chou, Yu-Hsun, Wu, Yen-Mo, Chung, Yi-Chen, Hsueh, Wei-Jen, Lin, Shih-Wei, Lu, Tien-Chang, Lin, Tzy-Rong, and Lin, Sheng-Di

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Abstract

Plasmonic devices have advanced significantly in the past decade. Being one of the most intriguing devices, plamonic nanolasers plays an important role in biomedicine, chemical sensor, information technology, and optical integrated circuits. However, nanoscale plasmonic devices, particularly in ultraviolet regime, are extremely sensitive to metal and interface quality, which renders the development of ultraviolet plasmonics. Here, by addressing the material issues, we demonstrate a low threshold, high characteristic temperature metal-oxide-semiconductor ZnO nanolaser working at room temperature. The template for ZnO nanowires consists of a flat single-crystalline aluminum film grown by molecular beam epitaxy and an ultra-smooth Al2O3 spacer layer prepared by atomic layer deposition. By effectively reducing surface plasmon scattering loss and metal intrinsic absorption loss, the high-quality metal film and sharp interfaces between layers boost the device performance. Our work paves the way for future applications using ultraviolet plasmonic nanolasers and related devices., Comment: 19 pages, 6 figures

Published
2015

10. Carrier–Phonon Interaction Induced Large Negative Thermal‐Optic Coefficient at Near Band Edge of Quasi‐2D (PEA) 2 PbBr 4 Perovskite

Author

Wu, Sheng‐Chan, primary, Wu, Chun‐Sheng, additional, Chien, Ching‐Hang, additional, Zhang, Yu‐Wei, additional, Yang, Chung‐Xian, additional, Liu, Cheng, additional, Li, Ming‐Hsien, additional, Lin, Chen‐Fu, additional, Wu, Yu‐Hao, additional, Lin, Bi‐Hsuan, additional, Chou, Yu‐Hsun, additional, Chang, Yia‐Chung, additional, Chen, Peter, additional, and Hsu, Hsu‐Cheng, additional

Published
2023
Full Text
View/download PDF

11. Controlled Cavity Length and Wide-Spectrum Lasing in FAMACsPb(BrI) 3 Ternary Perovskite Vertical-Cavity Surface-Emitting Lasers with an All-Dielectric Dielectric Bragg Reflector.

Author

Lin, Chiao-Chih, Chan, Pei-Wen, Chen, Peter, Wu, Zong Yu, Hsu, Hsu-Cheng, Lai, Wei-Chih, and Chou, Yu-Hsun

Subjects
SURFACE emitting lasers, PEROVSKITE, DIELECTRICS, TELECOMMUNICATION, OPTICAL communications, ACTIVE medium, COMMUNICATION of technical information
Abstract

In this study, we utilized a dielectric Bragg reflector (DBR) as a mirror and positioned a wide-spectrum FAMACsPb(BrI)3 halide perovskite film between two DBRs to construct a vertical-cavity surface-emitting laser (VCSEL) structure. The top and bottom DBRs were connected using optical adhesive, allowing us to control the cavity length by applying external force. Through this approach, we achieved operation at the desired wavelength. Due to the exceptional optical gain provided by FAMACsPb(BrI)3, we successfully observed multimode and lasing phenomena at room temperature under continuous-wave (CW) laser excitation. The outcomes of this study provide valuable insights for the application of novel VCSEL structures and highlight the potential of using FAMACsPb(BrI)3 halide perovskites in optical gain. This work holds significant implications for the fields of optical communication and laser technology. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

17. Carrier–Phonon Interaction Induced Large Negative Thermal‐Optic Coefficient at Near Band Edge of Quasi‐2D (PEA)2PbBr4 Perovskite.

Author

Wu, Sheng‐Chan, Wu, Chun‐Sheng, Chien, Ching‐Hang, Zhang, Yu‐Wei, Yang, Chung‐Xian, Liu, Cheng, Li, Ming‐Hsien, Lin, Chen‐Fu, Wu, Yu‐Hao, Lin, Bi‐Hsuan, Chou, Yu‐Hsun, Chang, Yia‐Chung, Chen, Peter, and Hsu, Hsu‐Cheng

Subjects
PEROVSKITE, BINDING energy, SEMICONDUCTOR materials, REFLECTANCE measurement, POLARITONS, HOT carriers, PHONON scattering, PHOTOTHERMAL effect
Abstract

The soft and polar nature of quasi‐2D (PEA)2PbBr4 perovskite, and robust photo‐generated excitons lead exciton‐polaritons and exciton‐polarons as the important phenomena near the band edge for application in the lighting aspect. In this work, a convenient methodology is proposed based on the polariton resonant modes in temperature‐dependent (77 K to RT) spectroscopy, and investigate the effect of these quasi‐particles on refractive index dispersion. The large binding energy (≈335 meV) of quasi‐2D excitons is obtained by the reflectance measurements at 77 K. Stable exciton‐polaritons and exciton‐polarons are confirmed by energy dispersions and the observation of self‐trapped exciton‐polaron state, respectively. Furthermore, the large negative thermal‐optic coefficient due to damping effect of exciton‐phonon scattering is observed. The phenomenon is opposite to those observed in conventional semiconductors (e.g., Si, Ge, GaN, AlN, GaAs, AlAs, and ZnO etc.). The observed stable negative thermal‐optic coefficients from 160 K to RT indicate that the quasi‐2D perovskite can be used as a phase compensator for conventional semiconductor materials. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

19. Tamm Plasmon‐Polariton Ultraviolet Lasers

Author

Xu, Wen-Hui, primary, Chou, Yu-Hsun, additional, Yang, Zih-Ying, additional, Liu, Yi-Yun, additional, Yu, Min-Wen, additional, Huang, Chen-Hang, additional, Chang, Chun-Tse, additional, Huang, Chen-Yu, additional, Lu, Tien-Chang, additional, Lin, Tzy-Rong, additional, and Chen, Kuo-Ping, additional

Published
2021
Full Text
View/download PDF

25. Perfect Absorption by an Atomically Thin Crystal

Author

Horng, Jason, primary, Martin, Eric W., additional, Chou, Yu-Hsun, additional, Courtade, Emmanuel, additional, Chang, Tsu-chi, additional, Hsu, Chu-Yuan, additional, Wentzel, Michael-Henr, additional, Ruth, Hanna G., additional, Lu, Tien-chang, additional, Cundiff, Steven T., additional, Wang, Feng, additional, and Deng, Hui, additional

Published
2020
Full Text
View/download PDF

27. Matrix phase induced boosting photoactive performance of ZnO nanowire turf‐coated Bi2O3 plate composites.

Author

Liang, Yuan‐Chang and Chou, Yu‐Hsun

Subjects
*ZINC oxide, *COMPOSITE plates, *NANOWIRES, *HETEROJUNCTIONS, *CHARGE exchange, *CRYSTAL growth
Abstract

A new nanocomposite consisting of ZnO nanowire turf‐coated Bi2O3 plates was synthesized using a method combining a chemical bath and hydrothermal crystal growth through sputtering ZnO seed layer‐assisted growth. Structural analysis revealed that highly crystalline, high‐density, one‐dimensional (1D) ZnO crystals were uniformly coated on the organized two‐dimensional (2D) Bi2O3 plates with a single β phase or dual α/β polymorphic phases. The Bi2O3–ZnO composites exhibited enhanced absorption properties in the ultraviolet and visible regions compared with pristine Bi2O3 and ZnO. Furthermore, the Bi2O3–ZnO composites exhibited higher photoactive performance than that of the pristine Bi2O3 and ZnO because of the low recombination rate of photoinduced electron−hole pairs caused by the vectorial transfer of electrons and holes between ZnO and Bi2O3 and the substantially increased surface area of the unique composite morphology. The ZnO nanowire turf‐coated Bi2O3 plates with a α/β‐Bi2O3 matrix exhibited photoelectrochemical and photocatalytic properties superior to those of the composite with a single β‐Bi2O3 matrix. The coexistence of α/β homojunction in the Bi2O3 matrix and the abundant heterojunctions between the ZnO nanowires and Bi2O3 plates substantially enhanced photoexcited charge separation efficiency. Growing high‐density 1D ZnO on 2D Bi2O3 via a combination methodology and crystallographic phase control provided a promising material design route for nanocomposite systems with high photoactivity for photoexcited device applications. [ABSTRACT FROM AUTHOR]

Published
2021
Full Text
View/download PDF

30. One- and Two-Photon Excited Photoluminescence and Suppression of Thermal Quenching of CsSnBr3Microsquare and Micropyramid

Author

Wu, Zong Yu, Zhuang, Jie-Hao, Lin, Yu-Tsung, Chou, Yu-Hsun, Wu, Pin Chieh, Wu, Chung-Lin, Chen, Peter, and Hsu, Hsu-Cheng

Abstract

Thermal photoluminescence (PL) quenching is fundamentally important for perovskite optoelectronic applications. Herein, we investigated PL characteristics of CsSnBr3microsquares and micropyramids synthesized by chemical vapor deposition (CVD) and their PL quenching behavior at high temperature. These microstructures have favorable PL performances in ambient atmosphere. Under two-photon excitation, we observed whispering gallery modes (WGMs) in microsquares and amplified spontaneous emission (ASE) in micropyramids. Reversible PL losses due to thermal effect were observed for both samples. Monotonic blue shifts in PL emission upon temperature increase suggest a band gap widening associated with an emphanisis effect. Temperature-dependent spectral line width analysis reveals that a line width broadening is attributed to the dominant electron–longitudinal optical phonon interaction. The estimated activation energy of thermally assisted nonradiative recombination for CsSnBr3microsquares and micropyramids is over 310 meV by the Arrhenius equation, which is higher than CsPbBr3. These results prove that CsSnBr3exhibits better thermal stability than Pb-based perovskites.

Published
2021
Full Text
View/download PDF

34. Ultracompact Pseudowedge Plasmonic Lasers and Laser Arrays

Author

Chou, Yu-Hsun, primary, Hong, Kuo-Bin, additional, Chang, Chun-Tse, additional, Chang, Tsu-Chi, additional, Huang, Zhen-Ting, additional, Cheng, Pi-Ju, additional, Yang, Jhen-Hong, additional, Lin, Meng-Hsien, additional, Lin, Tzy-Rong, additional, Chen, Kuo-Ping, additional, Gwo, Shangjr, additional, and Lu, Tien-Chang, additional

Published
2018
Full Text
View/download PDF

35. Metal for Plasmonic Ultraviolet Laser: Al or Ag?

Author

Chou, Yu-Hsun, primary, Hong, Kuo-Bin, additional, Chung, Yi-Cheng, additional, Chang, Chun-Tse, additional, Chou, Bo-Tsun, additional, Lin, Tzy-Rong, additional, Arakelian, Sergei M., additional, Alodjants, Alexander P., additional, and Lu, Tien-Chang, additional

Published
2017
Full Text
View/download PDF

47. Ultrastrong Mode Confinement in ZnO Surface Plasmon Nanolasers

Author

Chou, Yu-Hsun, primary, Chou, Bo-Tsun, additional, Chiang, Chih-Kai, additional, Lai, Ying-Yu, additional, Yang, Chun-Ting, additional, Li, Heng, additional, Lin, Tzy-Rong, additional, Lin, Chien-Chung, additional, Kuo, Hao-Chung, additional, Wang, Shing-Chung, additional, and Lu, Tien-Chang, additional

Published
2015
Full Text
View/download PDF

50. Ultraviolet Lasing in a ZnO Plasmonic Nanolaser

Author

Chou, Yu-Hsun, primary, Chou, Bo-Tsun, additional, Lai, Ying-Yu, additional, Yang, Chun-Ting, additional, Chiang, Chih-Kai, additional, Lin, Sheng-Di, additional, Lin, Tzy-Rong, additional, Lin, Chien-Chung, additional, Kuo, Hao-Chung, additional, Wang, Shing-Chung, additional, and Lu, Tien-Chang, additional

Published
2014
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results