Browsing by Author "Chen, Ross C. C."

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Bimodel onset strain relaxation in InAs quantum dots with an InGaAs capping layer
(2010-08-30)
Chen, J. F.
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Chen, Ross C. C.
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Chiang, C. H.
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Chen, Y. F.
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Wu, Y. H.
Capping InAs quantum dots (QDs) with an InGaAs layer allows strain relaxation to induce a low-energy electron state below a set of fine dot family states, which is consistent with photoluminescence (PL) spectra. The evolution of InAs thickness suggests a bimodal onset relaxation, i.e., a fine dot family that is strain-relieved by indium outdiffusion from the QDs, as suggested by transmission electron microscopy, and a low-energy dot family that is strain relaxed by the generation of lattice misfits. The indium outdiffusion can explain an abnormal PL blueshift in 70 meV in the fine dot family at onset of strain relaxation. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483757]
Compact efficient multi-GHz Kerr-lens mode-locked diode-pumped Nd:YVO(4) laser
(2008-12-08)
Liang, H. C.
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Chen, Ross C. C.
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Huang, Y. J.
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Su, K. W.
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Chen, Y. F.
We demonstrate the compact efficient multi-GHz Kerr-lens mode locking in a diode-pumped Nd:YVO(4) laser with a simple linear cavity without the need of any additional components. Experimental results reveal that the laser system can be characterized in stable single-pulse and multiple-pulse mode-locked operations. With a pump power of 2.5 W, the compact laser cavity produces average output powers greater than 0.8 W with a pulse width less than 10 ps in the range of 2-6 GHz. (C) 2008 Optical Society of America
Compensation effect and differential capacitance analysis of electronic energy band structure in relaxed InAs quantum dots
(2010-09-15)
Chen, J. F.
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Chen, Ross C. C.
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Chiang, C. H.
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Hsieh, M. C.
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Chang, Y. C.
The use of a differential capacitance technique for analyzing the effect of strain relaxation on the electronic energy band structure in relaxed InAs self-assembled quantum dots (QDs) is presented. Strain relaxation is shown to induce a deep defect state and compensate the ionized impurity in the bottom GaAs layer, leading to a double depletion width and a long emission time. An expression of capacitance at different frequency and voltage is derived for analyzing the experimental data. It has been shown that the relationship between the low-frequency and high-frequency capacitances can be well explained by a Schottky depletion model with a compensated concentration in the bottom GaAs layer. A simple expression is presented to account for the modulation of the free electrons in the top GaAs layer. This capacitance analysis shows a long low-energy tail for the electron ground state, suggesting not very uniform strain relaxation. The results of this study illustrate a carrier compensation effect of the defect state on the electronic energy band structure near the QDs. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467938]
Exploration of water jet generated by Q-switched laser induced water breakdown with different depths beneath a flat free surface
(2013-01-14)
Chen, Ross C. C.
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Yu, Y. T.
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Su, K. W.
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Chen, J. F.
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Chen, Y. F.
The dynamics of a water jet on a flat free surface are investigated using a nanosecond pulsed laser for creating an oscillating bubble with different depths beneath the free surface. A thin jet is shown to deform a crater surface resulted from surface depression and cause a circular ring-shaped crater on the connection surface between the crater of surface depression and the thin jet. The collapse of this circular ring-shaped crater is proposed to the crown-like formation around a thick jet. The evolution of the bubble depth suggests a classification of four distinctive ranges of the bubble depths: non-crown formation when the parameter of bubble depth over the maximum bubble radius gamma <= 0.5, unstable crown formation when 0.5 <= gamma <= 0.6, crown-like structure with a complete crown wall when 0.6 <= gamma <= 1.1, and non-crown formation when 1.1 <= gamma. Furthermore, the orientation of the crown wall gradually turns counterclockwise to vertical direction with increasing gamma from 0.5 to 1.1, implying a high correlation between the orientation of the crown wall and the depth of the bubble. This correlation is explained and discussed by the directional change of the jet eruption from the collapse of circular ring-shaped crater. (C)2013 Optical Society of America
Exploring morphological variations of a laser-induced water jet in temporal evolution: formation of an air bubble enclosing a water drop
(2013-11-01)
Chen, Ross C. C.
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Yu, Y. T.
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Su, K. W.
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Chen, Y. F.
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電子物理學系
We explore the spatio-temporal dynamics of a water jet that is generated by laser-induced water breakdown beneath a flat free surface. We find that morphological variations in the temporal evolution can be divided into three categories depending on the depth parameter gamma, which is the ratio of the water-breakdown depth to the maximum bubble radius. For a depth parameter in the range 0.8 <= gamma <= 1.03, we observe an intriguing pattern formation in which an air bubble perfectly encloses a water drop through the process of the Plateau-Rayleigh instability.
Exploring the origin of the directional emission from a microcavity with a large-aperture surface-emitting laser
(2009-06-15)
Chen, Ross C. C.
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Yu, Y. T.
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Huang, Y. J.
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Chen, C. C.
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Chen, Y. F.
The origin of the direction emission from a microcavity is investigated with a large-aperture surface-emitting laser with an equilateral-triangular shape. Experimental results reveal that a wide-spread eigen-mode and a localized superscar mode can display quite similar far-field directional emissions. This experimental finding is theoretically confirmed with the quantum-billiard wave function and the approximation of the paraxial propagation. (C) 2009 Optical Society of America
How do InAs quantum dots relax when the InAs growth thickness exceeds the dislocation-induced critical thickness?
(2012-01-01)
Chen, J. F.
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Lin, Y. C.
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Chiang, C. H.
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Chen, Ross C. C.
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Chen, Y. F.
A simple critical thickness for generating lattice misfits is insufficient to describe the onset strain relaxation in InAs quantum dots (QDs). A predominant dot family is shown to relieve its strain by In/Ga interdiffusion, rather than by lattice misfits, at the onset of strain relaxation. This argument is based on photoluminescence spectra, which show the emergence of a fine blueshifted transition at the onset of strain relaxation, along with a low-energy transition from a dot family degraded by lattice misfits. From the analysis of the temperature-dependent blueshift and energy separation between the ground and excited-state transitions, the blueshift is attributed to In/Ga interdiffusion. Transmission electron microscopy suggests a relaxation-induced indium migration from the interdiffused dot family to the dislocated dot family. Post-growth thermal annealing can further relieve strain by inducing more In/Ga interdiffusion in the interdiffused dot family and more dislocations in the dislocated dot family. This study explains the co-existence of strong carrier confinement in the QDs and enormous misfit-related traps in the capacitance-voltage spectra, and an elongated QD electron-emission time. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3675519]
Improving the photoluminescence properties of self-assembled InAs surface quantum dots by incorporation of antimony
(2011-08-15)
Chiang, C. H.
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Wu, Y. H.
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Hsieh, M. C.
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Yang, C. H.
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Wang, J. F.
This study investigates the effects of surfactant and segregation from InAs surface quantum dots (SQDs) by incorporating antimony (Sb) into the QD layers. The Sb surfactant effect extends planar growth and suppresses dot formation. Incorporating Sb can reduce the density of SQDs by more than two orders of magnitude. Photoluminescence (PL) reveals enhancement in the optical properties of InAs SQDs as the Sb beam equivalent pressure (BEP) increases. This improvement is caused by the segregation of Sb on the surface of SQDs, which reduces non-radiative recombination and suppresses carrier loss. The dark line at the SQDs surface in the transmission electron microscopic image suggests that the incorporated Sb probably segregates close to the surface of the SQDs. These results indicate a marked Sb segregation effect that can be exploited to improve the surface-sensitive properties of SQDs for biological sensing. Crown Copyright (C) 2011 Published by Elsevier B. V. All rights reserved.
Role of the N-related localized states in the electron emission properties of a GaAsN quantum well
(2011-11-15)
Hsieh, Meng-Chien
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Wang, Jia-Feng
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Wang, Yu-Shou
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Yang, Cheng-Hong
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Chen, Ross C. C.
This study elucidates the influence of the N-related localized states on electron emission properties of a GaAsN quantum well (QW) that is grown by molecular beam epitaxy. The N-related localized states in a GaAsN QW are identified as both optical and electrical electron trap states. Furthermore, exactly how N-related localized states influence the electron emission properties of a GaAsN quantum well is examined. The presence of N-related localized states effectively suppresses the tunneling emission of GaAsN QW electron states, leading to a long electron emission time for the GaAsN QW electron states. Thermal annealing can reduce the number of N-related localized states, resulting in a recovery of the tunneling emission for GaAsN QW electron states. Increasing the annealing temperature can restore the electron emission behavior of GaAsN QW to the typical electron tunneling emission for a high-quality QW. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3663436]
Transient Dynamics of Coherent Waves Released from Quantum Billiards and Analogous Observation from Free-Space Propagation of Laser Modes
(2009-01-30)
Chen, C. C.
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Yu, Y. T.
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Chen, Ross C. C.
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Huang, Y. J.
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Su, K. W.
The transient dynamics of the eigenstates and coherent states released from a square quantum billiard is analytically and numerically investigated. It is experimentally verified that this transient dynamic can be analogously observed with the free-space propagation of the lasing modes emitted from the laterally confined, vertically emitted cavities. Furthermore, we exploit a chaotically shaped cavity to originally demonstrate the diffraction-in-time characteristics of the chaotic wave functions. It is found that the transient patterns of chaotic wave functions exhibit a striking feature of random branching behavior with the appearance of intricate interference fringes.