Browsing by Author "Deng, Hui"

Now showing 1 - 7 of 7

Characteristics of exciton-polaritons in ZnO-based hybrid microcavities
(2011-02-28)
Chen, Jun-Rong
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Lu, Tien-Chang
;
Wu, Yung-Chi
;
Lin, Shiang-Chi
;
Hsieh, Wen-Feng
Wide bandgap semiconductors are promising materials for the development of polariton-based optoelectronic devices operating at room temperature (RT). We report the characteristics of ZnO-based microcavities (MCs) in the strong coupling regime at RT with a vacuum Rabi splitting of 72 meV. The impact of scattering states of excitons on polariton dispersion is investigated. Only the lower polariton branches (LPBs) can be clearly observed in ZnO MCs since the large vacuum Rabi splitting pushes the upper polariton branches (UPBs) into the scattering absorption states in the ZnO bulk active region. In addition, we systematically investigate the polariton relaxation bottleneck in bulk ZnO-based MCs. Angle-resolved photoluminescence measurements are performed from 100 to 300 K for different cavity-exciton detunings. A clear polariton relaxation bottleneck is observed at low temperature and large negative cavity detuning conditions. The bottleneck is suppressed with increasing temperature and decreasing detuning, due to more efficient phonon-assisted relaxation and a longer radiative lifetime of the polaritons. (C) 2011 Optical Society of America
Engineering radiative coupling of excitons in 2D semiconductors
(2019-11-20)
Horng, Jason
;
Chou, Yu-Hsun
;
Chang, Tsu-Chi
;
Hsu, Chu-Yuan
;
Lu, Tien-Chang
The resonance energy and the transition rate of atoms, molecules, and solids were understood as their intrinsic properties in classical electromagnetism. It was later realized that these quantities are linked to the radiative coupling between the transition dipole and photon modes. 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 in both absorption and emission spectroscopy the renormalization of the exciton resonance and the radiative decay rate in transition metal dichalcogenides monolayers due to their radiative interactions. Tuning the photon mode density near the monolayer, we demonstrate control of cooperative Lamb shift, radiative decay, and valley polarization of the excitons as well as control of the charged exciton emission. Our work establishes a technologically accessible and robust experimental system for engineering cooperative matter-light interactions. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Exciton-polaritons study in ZnO-based hybrid microcavities
(2012)
Lan, Yu-Pin
;
Lai, Ying-Yu
;
Huang, Si-Wei
;
Chen, Jun-Rong
;
Wu, Yung-Chi
The characteristics of exciton-polaritons in ZnO-based microcavities (MCs) are demonstrated with a large vacuum Rabi splitting due to large exciton binding energy and oscillator strength. The lower polariton branches (LPBs) can be clearly observed. For low temperature and large negative detuning conditions, a clear polariton relaxation bottleneck in bulk ZnO-based MCs has been observed in angle-resolved photoluminescence measurements from 100 to 353 K at different cavity-exciton detunings. The bottleneck is strongly suppressed with increasing the temperature and pumping power and reducing detuning. This observed results supposed to be due to more efficient phonon-assisted relaxation and a longer radiative lifetime of the polaritons. In addition, the linewidth broadening, blue-shift of the emission peak, and polarization of polariton lasing from below threshold to up threshold are also discussed.
Monolithically Integrated Multi-Color (Blue and Green) Light-Emitting Diode Chips
(2015)
Teng, Chu-Hsiang
;
Zhang, Lei
;
Tsai, Yu-Lin
;
Lin, Chien-Chung
;
Kuo, Hao-Chung
An LED chip with monolithically integrated, individually addressable multi-color pixels was demonstrated with a color tuning range from blue to green on a single epitaxial wafer.
Monolithically Integrated Multi-Color InGaN/GaN Nanopillar Light Emitting Diodes
(2015)
Teng, Chu-Hsiang
;
Zhang, Lei
;
Tsai, Yu-Lin
;
Lin, Chien-Chung
;
Kuo, Hao-Chung
Perfect Absorption by an Atomically Thin Crystal
(2020-08-05)
Horng, Jason
;
Martin, Eric W.
;
Chou, Yu-Hsun
;
Courtade, Emmanuel
;
Chang, Tsu-chi
Optical absorption is one of the most fundamental processes in light-matter interactions. The ability to achieve and control high absorption is crucial for a broad range of modern photonic technologies. In nanomaterials of length scales much smaller than a wavelength, optical absorption is typically a weak perturbation. To achieve high absorption, exquisite techniques and structures have been developed, such as coherent interference of multiple laser beams and plasmonic metasurfaces. Here, we show that a robust critical-coupling condition exists to allow perfect absorption of light by a subnanometer-thick two-dimensional semiconductor, when the radiative-decay rate of the exciton resonance balances with its loss rate. We measure an absorption up to 99.6% in a monomolecular MoSe2 crystal placed in front of a flat mirror. We furthermore demonstrate control of the perfect absorption by tuning the exciton-phonon, exciton-exciton, and exciton-photon interactions with temperature, pulsed laser excitation, and a movable mirror, respectively. Our work suggests a mechanism to achieve and control critical coupling in two-dimensional excitonic systems, enabling photonic applications including ultrafast low-power light modulators and sensitive optical sensing.
Room temperature polariton lasing vs. photon lasing in a ZnO-based hybrid microcavity
(2012-02-27)
Lu, Tien-Chang
;
Lai, Ying-Yu
;
Lan, Yu-Pin
;
Huang, Si-Wei
;
Chen, Jun-Rong
We report on the room temperature polariton lasing and photon lasing in a ZnO-based hybrid microcavity under optical pumping. A series of experimental studies of the polariton lasing (exciton-photon detunings of delta = -119meV) in the strong-coupling regime are discussed and compared to a photon lasing (delta = -45meV) in the weak-coupling regime obtained in the same structure. The measured threshold power density (31.8kW/cm(2)) of polariton lasing is one order of magnitude lower than that of the photon lasing (318.2kW/cm(2)). In addition, the comparison between polariton lasing and photon lasing is done in terms of the linewidth broadening, blue-shift of the emission peak, and polarization. (C) 2012 Optical Society of America