Browsing by Author "Lee, Yi-Shan"

Now showing 1 - 13 of 13

A Spin-controlled Microcavity Laser
(2015)
Hsu, Feng-Kuo
;
Xie, Wei
;
Lee, Yi-Shan
;
Lin, Sheng-Di
;
Lai, Chih-Wei
We demonstrate highly circularly polarized lasing under non-resonant elliptically polarized optical pumping in a semiconductor microcavity at room temperature. (C) 2014 Optical Society of America
Design and demonstration of high quality-factor H1-cavity in two-dimensional photonic crystal
(2013-11-15)
Fu, Ying-Jhe
;
Lee, Yi-Shan
;
Lin, Sheng-Di
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We introduce a method for designing an H1 photonic crystal cavity to enhance its quality factor (Q factor). The highest theoretical Q factor of 120,000 is obtained. The Fourier transformation of field distribution shows that the enhancement arises from the component reduction of a leaky mode. The Q-factor improvement has also been demonstrated experimentally with the highest value of 11,700. Our design could be useful for studying light-matter interaction in an H1 cavity as the mode volume only increases slightly. (C) 2013 Optical Society of America
High-quality planar light emitting diode formed by induced two-dimensional electron and hole gases
(2014-02-24)
Van-Truong Dai
;
Lin, Sheng-Di
;
Lin, Shih-Wei
;
Lee, Yi-Shan
;
Zhang, Yin-Jie
A high-quality planar two-dimensional p-i-n light emitting diode in an entirely undoped GaAs/AlGaAs quantum well has been fabricated by using conventional lithography process. With twin gate design, two-dimensional electron and hold gases can be placed closely on demand. The electroluminescence of the device exhibit high stability and clear transition peaks so it is promising for applications on electrically-driven single photon sources. (C) 2014 Optical Society of America
Method to evaluate afterpulsing probability in single-photon avalanche diodes
(2015-08-15)
Tzou, Bo-Wei
;
Wu, Jau-Yang
;
Lee, Yi-Shan
;
Lin, Sheng-Di
;
電機工程學系
We propose and demonstrate a new method for evaluating the afterpulsing effect in single-photon avalanche photodiodes (SPADs). By analyzing the statistical property of dark count rate, we can quantitatively characterize afterpulsing probability (APP) of a SPAD. In experiment, the temperature-dependent low dark count rate (DCR) distribution becomes non-Poissonian at lower temperature and has higher excess bias as the afterpulsing effect becomes significant. Our work provides a flexible way to examine APP in either single-device or circuit level. (C) 2015 Optical Society of America
Multiple-pulse microcavity lasing from an optically induced confinement
(2016-12-20)
Xie, Wei
;
Hsu, Feng-kuo
;
Lee, Yi-Shan
;
Lin, Sheng-Di
;
Lai, Chih Wei
Coupled electron-hole-photon systems in semiconductor microcavities have been a platform for studies of laser dynamics and nonequilibrium cooperative phenomena in solid states. Here, we report the observation of multiple-pulse lasing in optically induced confinement in a highly photoexcited semiconductor microcavity at room temperature. The spatially photomodulated refractive index changes enable an additional lateral photonic confinement, and discrete transverse modes result. Temporally and spectrally resolved measurements of the radiation reveal multiple sub-10-ps pulsed radiation commencing in order from high-to low-energy modes. Under a circularly polarized optical pumping, the high-energy mode emerges within 10 ps after the pulsed excitation and has a near-unity circular polarization. We attribute the observed cooperative effects to light-induced correlated e-h pairs in a high-density plasma and their effective coupling to discrete transverse modes in the spatially photomodulated optical confinement. (C) 2016 Optical Society of America
POLARIZATION-RESOLVED STRONG COUPLING OF FINE-STRUCTURE SPLIT EXCITONS AND MICROCAVITIES
(2014-01-01)
Lee, Yi-Shan
;
Lin, Sheng-Di
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We investigate the fine-structure split excitons strongly coupled to photons in a micropillar by using the polarization-resolved micro-photoluminescence. Different coupling strengths are probed for the two excitons coupled respectively to the two polarized fundamental cavity modes. The orientation of energy states for both upper and lower exciton-polaritons is found rotating with the coupling due to the misorientation of exciton dipoles with the cavity modes. The polarization properties of this coherently exciton-photon coupling will also be presented.
Polarized emission of quantum dots in microcavity and anisotropic Purcell factors
(2014-01-27)
Lee, Yi-Shan
;
Lin, Sheng-Di
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We study the polarization properties of quantum dot (QD) emission coupled with the fundamental cavity modes. A rotation of polarization axis and a change of polarization degree are observed as the coupling is varied. To explain this observation, we derive an analytical model considering the polarization misalignment between QD dipole and cavity mode field. Our model also provides a new approach to extract the anisotropic Purcell factors by analyzing the polarization of detected quantum dot emission coupled to the cavity mode, which paves the way to develop high-efficiency polarized single photon sources. (C) 2014 Optical Society of America
Role of incoherent pumping in a strongly coupled system of exchange-split excitons and pillar-microcavities
(2014-12-01)
Lee, Yi-Shan
;
Lin, Sheng-Di
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We present an experimental study of the influence of incoherent pumping upon the strong coupling between quantum dot excitons and a micropillar-cavity. For two exchange-split excitons, the inherent difference in the detuning with respect to the cavity modes leads to an unequal reduction of Rabi splitting for two orthogonal polarizations as excitation power is increased, which could destroy the indistinguishable decay paths built by the coupled states. This work prompts a careful implementation of optical pumping for the pursuit of polarization-entangled photon pairs in the strong coupling regime. (C) 2014 Optical Society of America
Room-Temperature Macroscopic Coherence of Two Electron-Hole Plasmas in a Microcavity
(2020-04-16)
Jie, Qi
;
Zhang, Keye
;
Lai, Chih-Wei
;
Hsu, Feng-Kuo
;
Zhang, Weiping
Macroscopic coherence of Bose condensates is a fundamental and practical phenomenon in many-body systems, such as the long-range correlation of exciton-polariton condensates with a dipole density typically below the exciton Mott-transition limit. Here we extend the macroscopic coherence of electron-hole-photon interacting systems to a new region in the phase diagram-the high-density plasma region, where long-range correlation is generally assumed to be broken due to the rapid dephasing. Nonetheless, a cooperative state of electron-hole plasma does emerge through the sharing of the superfluorescence field in an optical microcavity. In addition to the in situ coherence of e-h plasma, a long- range correlation is formed between two 8-mu m-spaced plasma ensembles even at room temperature. Quantized and self-modulated correlation modes are generated for e-h ensembles in the plasma region. By controlling the distance between the two ensembles, multiple coupling regimes are revealed, from strong correlation to perturbative phase correlation and finally to an incoherent classical case, which has potential implications for tunable and high-temperature-compatible quantum devices.
Selecting detection wavelength of resonant cavity-enhanced photodetectors by guided-mode resonance reflectors
(2012-02-13)
Lai, Kuo-Wei
;
Lee, Yi-Shan
;
Fu, Ying-Jhe
;
Lin, Sheng-Di
;
電子工程學系及電子研究所
We propose and demonstrate a novel device structure of resonant cavity-enhanced photodetector (RCE-PD). The new RCE-PD structure consists of a bottom distributed Bragg reflector (DBR), a cavity with InGaAs multiple quantum wells (MQWs) for light absorption and a top mirror of sub-wavelength grating. By changing the fill factor of the 2-D grating, the effective cavity length of RCE-PDs can be varied so the resonant wavelength can be selected post growth. Accordingly, we can fabricate an array of PDs on a single chip, on which every PD aims for a specific wavelength. (C) 2012 Optical Society of America
Stress tuning of strong and weak couplings between quantum dots and cavity modes in microdisk microcavities
(2011-11-01)
Lin, Hsuan
;
Lin, Chia-Hsien
;
Lai, Wei-Chen
;
Lee, Yi-Shan
;
Lin, Sheng-Di
We present the control of couplings between quantum dots and cavity modes in microdisk microcavities by a stress tuning scheme. The excitonic transitions and cavity modes can be brought into resonance due to their different energy shift rates with the applied strain. Spectral signatures of both strong and weak couplings are clearly observed. The strain tunable device can be used to tune the exciton wavelength bidirectionally at constant temperatures without significantly affecting the emission rate and linewidth of excitons.
Transient dual-energy lasing in a semiconductor microcavity
(2015-10-19)
Hsu, Feng-Kuo
;
Xie, Wei
;
Lee, Yi-Shan
;
Lin, Sheng-Di
;
Lai, Chih Wei
We demonstrate sequential lasing at two well-separated energies in a highly photoexcited planar microcavity at room temperature. Two spatially overlapped lasing states with distinct polarization properties appear at energies more than 5 meV apart. Under a circularly polarized nonresonant 2 ps pulse excitation, a sub-10-ps transient circularly polarized high-energy (HE) state emerges within 10 ps after the pulse excitation. This HE state is followed by a pulsed state that lasts for 20-50 ps at a low energy (LE) state. The HE state is highly circularly polarized as a result of a spin-preserving stimulated process, while the LE state shows a significantly reduced circular polarization because of a diminishing spin imbalance.
Ultrafast spin-polarized lasing in a highly photoexcited semiconductor microcavity at room temperature
(2015-05-14)
Hsu, Feng-kuo
;
Xie, Wei
;
Lee, Yi-Shan
;
Lin, Sheng-Di
;
Lai, Chih-Wei
We demonstrate room-temperature spin-polarized ultrafast (similar to 10 ps) lasing in a highly optically excited GaAs microcavity. This microcavity is embedded with InGaAs multiple quantum wells in which the spin relaxation time is less than 10 ps. The laser radiation remains highly circularly polarized even when excited by nonresonant elliptically polarized light. The lasing energy is not locked to the bare cavity resonance, and shifts similar to 10 meV as a function of the photoexcited density. Such spin-polarized lasing is attributed to a spin-dependent stimulated process of correlated electron-hole pairs. These pairs are formed near the Fermi edge in a high-density electron-hole plasma coupled to the cavity light field.