Browsing by Author "Lai, Ying-Yu"

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Crossover from polariton lasing to exciton lasing in a strongly coupled ZnO microcavity
(2016-02-03)
Lai, Ying-Yu
;
Chou, Yu-Hsun
;
Lan, Yu-Pin
;
Lu, Tien-Chang
;
Wang, Shing-Chung
Unlike conventional photon lasing, in which the threshold is limited by the population inversion of the electron-hole plasma, the exciton lasing generated by exciton-exciton scattering and the polariton lasing generated by dynamical condensates have received considerable attention in recent years because of the sub-Mott density and low-threshold operation. This paper presents a novel approach to generate both exciton and polariton lasing in a strongly coupled microcavity (MC) and determine the critical driving requirements for simultaneously triggering these two lasing operation in temperature <140 K and large negative polariton-exciton offset (<-133 meV) conditions. In addition, the corresponding lasing behaviors, such as threshold energy, linewidth, phase diagram, and angular dispersion are verified. The results afford a basis from which to understand the complicated lasing mechanisms in strongly coupled MCs and verify a new method with which to trigger dual laser emission based on exciton and polariton.
Curvature-assisted wave localization in Vertical Cavity Surface Emitting Lasers
(2017-01-01)
Hong, Kou-Bin
;
Lin, Chun-Yan
;
Chang, Tsu-Chi
;
Liang, Wei-Hsuan
;
Lai, Ying-Yu
By implementing surface structures in vertical cavity surface emitting lasers as manifolds for curved space, we experimentally study the impacts of geometrical constraints on wave localization. We observe localized waves pinned to the maximal curvature in an ellipticalring, and confirm the reduction in the localization length of waves by measuring near and far field patterns, as well as the corresponding dispersion relation. Theoretically, analyses based on a dissipative model with a parabola curve give good agreement remarkably to experimental measurement on the transition from delocalized to localized waves. The introduction of curved topology allows to control and design lasing modes in the nonlinear regime.
Efficient Defect Healing of Transition Metal Dichalcogenides by Metallophthalocyanine
(2018-08-29)
Ahn, Hyeyoung
;
Huang, Yu-Chiao
;
Lin, Chang-Wei
;
Chiu, Yi-Lun
;
Lin, Erh-Chen
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted great attention as alternatives to graphene with semiconducting band gaps. Mono- or few-layer TMDCs can be prepared by various methods, but regardless of the fabrication methods [such as mechanical exfoliation and chemical vapor deposition (CVD)], TMDCs contain many structural defects, which significantly affect their physical properties and limit their performance in applications. Metallophthalocyanines (MPcs) are organic semiconductors, and as dopants, they are capable of modulating the optical and electrical properties of other semiconducting materials. Here, we report that besides the ability to modulate the optoelectronic properties of 2D TMDCs, MPc molecules can be used to heal defects and improve the physicochemical properties of TMDCs. Doping of planar MPc molecules to TMDCs is achieved by a simple solution dip-coating method and results in a significant improvement in the optical properties and thermal responses of CVD-grown TMDCs, even comparable to those of mechanically exfoliated counterparts. Study of carrier dynamics shows that the adsorption of MPc on the TMDC surface leads to the complete suppression of the mid-gap defect-induced absorption in TMDCs. Furthermore, MPc molecules with a large lateral size are found to effectively reduce the point defects in mechanically exfoliated TMDCs introduced during the preparation process. Our results not only clarify the optoelectronic modulation mechanism of chemical doping but also offer a simple method to control the nanosized defects in 2D TMDCs.
Electrically Pumped III-N Microcavity Light Emitters Incorporating an Oxide Confinement Aperture
(2017-01-05)
Lai, Ying-Yu
;
Chang, Tsu-Chi
;
Li, Ya-Chen
;
Lu, Tien-Chang
;
Wang, Shing-Chung
In this work, we report on electrically pumped III-N microcavity (MC) light emitters incorporating oxide confinement apertures. The utilized SiO2 aperture can provide a planar ITO design with a higher index contrast (similar to 1) over other previously reported approaches. The fabricated MC light emitter with a 15-mu m-aperture shows a turn-on voltage of 3.3 V, which is comparable to conventional light emitting diodes (LEDs), showing a good electrical property of the proposed structure. A uniform light output profile within the emission aperture suggesting the good capability of current spreading and current confinement of ITO and SiO2 aperture, respectively. Although the quality factor (Q) of fabricated MC is not high enough to achieve lasing action (similar to 500), a superlinear emission can still be reached under a high current injection density (2.83 kA/cm(2)) at 77 K through the exciton-exciton scattering, indicating the high potential of this structure for realizing excitonic vertical-cavity surface-emitting laser (VCSEL) action or even polariton laser after fabrication optimization.
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.
Fabrication and characteristics of a GaN-based microcavity laser with shallow etched mesa
(2014-06-01)
Lai, Ying-Yu
;
Chou, Yu-Hsun
;
Wu, Yu-Sheng
;
Lan, Yu-Pin
;
Lu, Tien-Chang
In this work, we have developed a simple GaN-based microcavity (MC) with an intracavity shallow etched mesa. The textured GaN-based MC incorporated two high-reflectivity dielectric Bragg mirrors and an InGaN/GaN multiple quantum well with a shallow etched mesa as an optical confined structure. Lasing and transverse optical confinement characteristics have been verified by measuring devices with different mesa diameters. A quality factor (Q) of 2600 and a threshold energy of 30 nJ have been observed in a 10-mu m-diameter device. Such a cavity structure could be implanted into electrically pumped GaN vertical-cavity surface-emitting lasers for supporting efficient transverse confinement. (C) 2014 The Japan Society of Applied Physics
Fabrication and characteristics of a GaN-based microcavity laser with shallow etched mesa
(2014-06-01)
Lai, Ying-Yu
;
Chou, Yu-Hsun
;
Wu, Yu-Sheng
;
Lan, Yu-Pin
;
Lu, Tien-Chang
In this work, we have developed a simple GaN-based microcavity (MC) with an intracavity shallow etched mesa. The textured GaN-based MC incorporated two high-reflectivity dielectric Bragg mirrors and an InGaN/GaN multiple quantum well with a shallow etched mesa as an optical confined structure. Lasing and transverse optical confinement characteristics have been verified by measuring devices with different mesa diameters. A quality factor (Q) of 2600 and a threshold energy of 30 nJ have been observed in a 10-mu m-diameter device. Such a cavity structure could be implanted into electrically pumped GaN vertical-cavity surface-emitting lasers for supporting efficient transverse confinement. (C) 2014 The Japan Society of Applied Physics
Fabrication of SiC Membrane HCG Blue Reflector Using Nanoimprint Lithography
(2015-01-01)
Lai, Ying-Yu
;
Matsutani, Akihiro
;
Lu, Tien-Chang
;
Wang, Shing-Chung
;
Koyama, Fumio
We designed and fabricated a suspended SiC-based membrane high contrast grating (HCG) reflectors. The rigorous coupled-wave analysis (RCWA) was employed to verify the structural parameters including grating periods, grating height, filling factors and air-gap height. From the optimized simulation results, the designed SiC-based membrane HCG has a wide reflection stopband (reflectivity (R) > 90%) of 135 nm for the TE polarization, which centered at 480 nm. The suspended SiC-based membrane HCG reflectors were fabricated by nanoimprint lithography and two-step etching technique. This achievement should have an impact on numerous III-N based photonic devices operating in the blue wavelength or even ultraviolet region.
GaN-based microcavity polariton light emitting diodes
(2012)
Lu, Tien-Chang
;
Lai, Ying-Yu
;
Huang, Si-Wei
;
Chen, Jun-Rong
;
Wu, Yung-Chi
Here we report the first realization of a current injection microcavity GaN exciton-polariton light emitting diode (LED) operating under room temperature (RT). The hybrid microcavity structure consists of InGaN/GaN quantum wells sandwiched between bottom epitaxial DBR and top dielectric DBR. The anti-crossing behavior of polariton LED denotes a clear signature of the strong interaction between excitons and cavity photons.
Generation of Crescent Waves in Vertical Cavity Surface Emitting Lasers with an Surface Elliptical Ring
(2014)
Lai, Ying-Yu
;
Chang, Tsu-Chi
;
Li, Ya-Chen
;
Lin, Chun-Yan
;
Lu, Tien-Chang
We tailor the lasing modes in the vertical cavity surface -emitting laser into a crescent wave using a surface elliptical ring. The crescent wave was observed to be localized at the semi-major axis of elliptical ring.
High-Temperature Polariton Lasing in a Strongly Coupled ZnO Microcavity
(2012-08-01)
Lai, Ying-Yu
;
Lan, Yu-Pin
;
Lu, Tien-Chang
;
光電工程學系
;
Department of Photonics
We report on the observation of polariton lasing in a negative detuned ZnO hybrid microcavity at room temperature (300 K) with threshold of 12.38 mu J/cm(2) and at high temperature (353 K) with a higher threshold of 53.05 mu J/cm(2) due to a stronger thermal escape process and a shallower polariton trap. The decoherence mechanism of the polariton laser due to the polariton self-interaction was investigated by power-dependent photoluminescence and Michelson interference measurements. The spatial coherence length r(c) similar to 0.26 mu m of the polariton laser was obtained from Young's double slits. (C) 2012 The Japan Society of Applied Physics
Lasing in a ZnO membrane microcavity with designable shape fabricated by focused ion beam milling
(2015)
Chang, Tsu-Chi
;
Lai, Ying-Yu
;
Chou, Yu-Hsun
;
Lu, Tien-Chang
;
照明與能源光電研究所
We show a three-dimensional membrane cavity fabrication technique and corresponding lasing characteristics of the fabricated rectangular ZnO membrane microcavity (MC) using optical injection. The ZnO membrane was cut from a single crystalline ZnO substrate by using a focused ion beam, and was then placed onto a SiO2 substrate by using a glass tip. The micro-photoluminescence measurement performed on the fabricated ZnO membrane MC at 77 K showed an obvious feature of lasing action including non-linear increasing of intensity and linewidth narrowing. By using this fabrication approach, various MCs with desired shapes can be made.
Lasing on nonlinear localized waves in curved geometry
(2017-11-13)
Hong, Kou-Bin
;
Lin, Chun-Yan
;
Chang, Tsu-Chi
;
Liang, Wei-Hsuan
;
Lai, Ying-Yu
The use of geometrical constraints exposes many new perspectives in photonics and in the fundamental studies of nonlinear waves. By implementing surface structures in vertical cavity surface emitting lasers as manifolds for curved space, we experimentally study the impacts of geometrical constraints on nonlinear wave localization. We observe localized waves pinned to the maximal curvature in an elliptical-ring, and confirm the reduction in the localization length of waves by measuring near and far field patterns, as well as the corresponding energy-angle dispersion relation. Theoretically, analyses based on a dissipative model with a parabola curve give good agreement remarkably to experimental measurement on the reduction in the localization length. The introduction of curved geometry allows to control and design lasing modes in the nonlinear regime. (C) 2017 Optical Society of America
Manipulation of exciton and photon lasing in a membrane-type ZnO microcavity
(2015-03-30)
Lai, Ying-Yu
;
Chen, Jee-Wei
;
Chang, Tsu-Chi
;
Chou, Yu-Hsun
;
Lu, Tien-Chang
We report on the fabrication and characterization of a membrane-type ZnO microcavity (MC). The ZnO membrane was cut from a single crystalline ZnO substrate by using focused ion beam milling, and was then placed onto a SiO2 substrate by using glass microtweezers. Through changing the pumping regime, manipulation of P-band exciton lasing and whispering-gallery mode (WGM) photon lasing could be easily achieved. P-band exciton lasing was observed only when the pumping laser was focused at the center of the ZnO MC with a small pumping size because of the innate ring-shaped WGM distribution. Furthermore, the lasing threshold of the ZnO MC could be reduced to an order lower by using a larger pumping spot because of the more favorable spatial overlap between the optical gain and WGM. (C) 2015 AIP Publishing LLC.
Numerical analysis on current and optical confinement of III-nitride vertical-cavity surface-emitting lasers
(2014-04-21)
Lai, Ying-Yu
;
Huang, Shen-Che
;
Ho, Tsung-Lin
;
Lu, Tien-Chang
;
Wang, Shing-Chung
We report on the numerical analysis of the electrical and optical properties of current-injected III-nitride based vertical-cavity surface-emitting lasers (VCSELs) with three types of current confinement schemes: the conventional planar-indium tin oxide (ITO) type, the AlN-buried type without ITO, and the hybrid type. The proposed hybrid structure, which combines an ITO layer and an intracavity AlN aperture, exhibits not only uniform current distribution but also enhanced lateral optical confinement. Thus, the hybrid type design shows remarkably better performance including lower threshold current and series resistance compared with the planar-ITO type and the AlN-buried type. Furthermore, the multi-transverse mode lasing behavior induced by strong index guiding of the AlN aperture is suppressed to single transverse mode operation by reducing the aperture size. Such design provides a powerful solution for the high performance III-N based VCSELs and is also viable by using current state of the art processing techniques. (C) 2014 Optical Society of America
Numerical Analysis on Current and Optical Confinement of III-Nitride Vertical-Cavity Surface-Emitting Lasers
(2014)
Lai, Ying-Yu
;
Lu, Tien-Chang
;
Ho, Tsung-Lin
;
Huang, Shen-Che
;
Wang, Shing-Chung
We report on the numerical analysis of the electrical and optical properties of current-injected III-N based vertical-cavity surface-emitting lasers (VCSELs) with three types of current confinement schemes: the conventional planar-Indium Tin Oxide (ITO) type, the AlN-buried type without ITO, and the hybrid type. The proposed hybrid structure, which combines an ITO layer and an intracavity AlN aperture, exhibits not only a uniform current distribution but also an enhanced lateral optical confinement. Thus, the hybrid type design shows a remarkably better performance including lower threshold current and series resistance compared with the planar-ITO type and the AlN-buried type. Furthermore, the multi-transverse mode lasing behavior induced by strong index guiding of the AlN aperture is suppressed to single transverse mode operation by reducing the aperture size. Such design provides a powerful solution for the high performance III-N based VCSELs and is also viable by using current state of the art processing techniques.
Polariton Lasing in a ZnO-based Microcavity up to 353K
(2012)
Lai, Ying-Yu
;
Lan, Yu-Pin
;
Huang, Si-Wei
;
Lu, Tien-Chang
;
Wang, Shing-Chung
We report the polariton lasing at temperature up to 353K in a ZnO-based microcavity. The large exciton binding energy and Rabi-splitting of ZnO ensuring the strong coupling regime is maintained at high temperature.
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
Simultaneous Lasing of Exciton and Polariton in a ZnO Microcavity
(2016)
Yu-HsunChou
;
Lai, Ying-Yu
;
Lu, Tien-Chang
;
Shing-ChungWang
;
照明與能源光電研究所
We have performed the condition to simultaneously triggered exciton-related polariton lasing and P-line exciton lasing in a ZnO micorcavity and verified the characteristics of their lasing behaviors. In addition, the threshold energy, linewidth, phase diagram, and angular dispersion are verified and discussed.
Strong light-matter interaction in ZnO microcavities
(2013-06-01)
Lai, Ying-Yu
;
Lan, Yu-Pin
;
Lu, Tien-Chang
;
光電工程學系
;
Department of Photonics
The strong light-matter interaction in ZnO-embedded microcavities has received great attention in recent years, due to its ability to generate the robust bosonic quasiparticles, exciton-polaritons, at or above room temperature. This review introduces the strong coupling effect in ZnO-based microcavities and describes the recent progress in this field. In addition, the report contains a systematic analysis of the room-temperature strong-coupling effects from relaxation to polariton lasing. The stable room temperature operation of polaritonic effects in a ZnO microcavity promises a wide range of practical applications in the future, such as ultra-low power consumption coherent light emitters in the ultraviolet region, polaritonic transport, and other fundamental of quantum optics in solid-state systems.