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470 results on '"Wang, Qu-Quan"'

108. Intensity-Dependent Optical Nonlinear Absorption and Refraction of Gold Nanorods

Author

Zhou Zhang-Kai, Xiao Si, Song Hao, SU Xiong-Rui, Li Min, Gong Hong-Mei, and Wang Qu-Quan

Subjects
Materials science, Absorption spectroscopy, Extended X-ray absorption fine structure, business.industry, Physics::Medical Physics, Physics::Optics, General Physics and Astronomy, Laser, Refraction, Molecular physics, Two-photon absorption, law.invention, Optics, law, Nanorod, Absorption (electromagnetic radiation), business, Refractive index
Abstract

Au nanorods dispersed in aqueous solution were prepared with the electrochemical method. The absorption spectrum shows two absorption peaks corresponding to the perpendicular and transverse surface plasma resonance absorption of the nanorods. The third-order optical nonlinear properties are investigated by Z-scans. The signs of the nonlinear absorption coefficient and refractive index are reversed as the intensity of incident laser increases, which is due to the shape change of the gold nanoparticles melted by the intense laser pulses.

Published
2007

109. Demonstration of Inverse Scattering Transform for DNLS Equation

Author

Huang Nian-Ning, Yang Chun-Nuan, YU Jia-Lu, and Wang Qu-Quan

Subjects
Physics and Astronomy (miscellaneous), Inverse scattering transform, Mathematical model, Simple (abstract algebra), Inverse scattering problem, Compatibility (mechanics), Applied mathematics, Mathematical physics, Mathematics
Abstract

Since the Jost solutions of the DNLS equation does not tend to the free Jost solutioins as | | ! 1, the usual inverse scattering transform (IST) must be revised. Beside the Kaup and Newell's approach, we propose a simple revision in constructing the equations of IST, where the usual Zakharov-Shabat kern is revised by multiplying 2 or 1 . To justify the revision we show that the Jost solutions obtained do satisfy the pair of compatibility equations.

Published
2007

112. Growth of Au Hollow Stars and Harmonic Excitation Energy Transfer

Author

Qiu, Yun-Hang, Ding, Si-Jing, Lin, Yong-Jie, Chen, Kai, Yang, Da-Jie, Ma, Song, Li, Xiaoguang, Lin, Hai-qing, Wang, Jianfang, and Wang, Qu-Quan

Abstract

Optical excitation, subsequent energy transfer, and emission are fundamental to many physical problems. Optical antennas are ideal candidates for manipulating these processes. We extend energy transfer to second- and third-harmonic (SH and TH) fields through the collaborative susceptibility χ(n)(n= 1, 2, 3) resonances of nonlinear optical antennas. Hollow gold stars, with a broadband response covering the fundamental, SH, and TH frequencies, are synthesized as nonlinear antennas. Harmonic resonance energy transfer through a χ(3)→ χ(1)collaboration is revealed. A χ(3)→ χ(2)collaboration is uncovered, with largely enhanced SH radiation demonstrated by exciting the three resonances at the fundamental, SH, and TH frequencies. A theoretical model of the effective nonlinear susceptibilities is proposed to calculate the efficiencies of the two nonlinear energy transfer processes.

Published
2020
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113. One- and Two-Photon Excited Fluorescence of CdSe and CdSe/ZnS Quantum Dots in n-Hexane

Author

Wang Qu-Quan, Hao Zhong-Hua, Gong Hong-Mei, Zhai Yue-Ying, and Han Jun-Bo

Subjects
Nonlinear absorption, Materials science, Passivation, Condensed Matter::Other, Physics::Optics, General Physics and Astronomy, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Photochemistry, Fluorescence, Hexane, Condensed Matter::Materials Science, chemistry.chemical_compound, Two-photon excitation microscopy, chemistry, Quantum dot, Excited state, Absorption (electromagnetic radiation)
Abstract

One- and two-photon absorption and excited fluorescence of the CdSe and the core-shell structure CdSe/ZnS quantum dots (QDs) in n-hexane is investigated. The linear and nonlinear absorption coefficients are measured and the two-photon-absorption cross sections of the QDs are also obtained. For both one-photon fluorescence and two-photon fluorescence, the emission efficiency of CdSe/ZnS is much higher than that of CdSe, originating from the effective surface passivation of the core-shell structure.

Published
2006

115. Controlled growth of CdS–Cu2−xS lateral heteroshells on Au nanoparticles with improved photocatalytic activity and photothermal efficiency.

Author

Ma, Song, Chen, Kai, Qiu, Yun-Hang, Gong, Li-Li, Pan, Gui-Min, Lin, Yong-Jie, Hao, Zhong-Hua, Zhou, Li, and Wang, Qu-Quan

Abstract

Substantial effort has been devoted to synthesizing plasmonic metal/semiconductor heteronanostructures with controlled morphology owing to their excellent performance ranging from photocatalysis to optical information processing. However, growing semiconductor heterojunctions with both counterparts in direct contact with the plasmonic metal nanostructures remains challenging. Herein, we report a three-step method to grow CdS–Cu2−xS lateral heteroshells on Au nanoparticles with all components directly connected with each other. Ag2S semi shells are initially grown on the Au nanoparticles as an interim layer, Cu2−xS semi shells are then grown on the uncovered surface of the Au nanoparticles, and CdS is generated by replacing Ag2S and the Au core complex with CdS–Cu2−xS lateral heteroshells Au/CdS–Cu2−xS is finally obtained. These complexes integrate the plasmon resonances of Au in the visible region and that of Cu2−xS in the near-infrared region, and therefore show improved photocatalytic activity and high photothermal efficiency. This study offers a synthetic approach to grow metal sulfides on Au nanostructures which have diverse applications in photocatalysis and photothermal therapy. [ABSTRACT FROM AUTHOR]

Published
2019
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117. A Sign Alternation of Nonlinear Absorption in Gold Composite Films in Z-Scan

Author

Xiao Si, Han Jun-Bo, Wang Qu-Quan, Ding Sha, Zhou Hui-Jun, Chen Dai-Jian, and Xiong Gui-guang

Subjects
Optical nonlinearity, Nonlinear absorption, Materials science, Reverse saturable absorption, Femtosecond, Composite number, Analytical chemistry, Alternation (geometry), General Physics and Astronomy, Z-scan technique, Atomic physics, Saturation (magnetic)
Abstract

Au–TiO2 composite films with Au atom content varying from about 15% to 82% are prepared by co-sputtering technique. Both open- and closed-aperture Z-scan of the samples are performed in the femtosecond time region. A conversion of the nonlinear absorption from negative to positive is observed as the Au atom content increases due to the saturation of reverse saturable absorption. The nonlinear refractive index γ and effective nonlinear absorption coefficient βeff at the Au atom content of 54% are measured to be 1.6×10−2 cm2/GW and −2.6×103 cm/GW, respectively. The corresponding third-order optical nonlinearity χ(3) is about 6.3×10−8 esu.

Published
2005

118. Optical realization of wavelet transform with a single lens

Author

Li Cheng-fang, Wang Qu-Quan, Xiong Gui-guang, Wang Lin, and Zhang Su-huai

Subjects
Discrete wavelet transform, Physics, Lifting scheme, business.industry, Stationary wavelet transform, Second-generation wavelet transform, Physics::Optics, General Physics and Astronomy, Wavelet transform, Wavelet packet decomposition, Optics, Wavelet, business, Harmonic wavelet transform
Abstract

Two optical set-ups to implement wavelet transform with a single lens have been proposed, in which the wavelet filter was placed in front of the imaging lens or on the frequency plane. The general formula of the complex field distribution of the output plane has been deduced. The analysing wavelet functions of the band-pass wavelet filters with double and circular slits have been discussed.

Published
2001

130. Second-Order Correlation Function of the Photon Emission from a Single Quantum Dot

Author

Wang Qu-Quan, Cheng Mu-Tian, Li Yao-Yi, Liu Shao-Ding, and Zhou Hui-Jun

Subjects
Optical pumping, Physics, Correlation function, Quantum dot, Interaction picture, Master equation, General Physics and Astronomy, Order (ring theory), Rate equation, Atomic physics, Excitation
Abstract

The photon correlation of photon emission from a single quantum dot with cw excitation and pulsed excitation is investigated in details. To calculate the second-order correlation function for optical pumping, we deduce rate equations with a simplified two-level model under cw excitation and present the master equation approach in the interaction picture to the study of evolution of a three-level system under pulsed excitation. In addition, we report photon correlation measurements on a single self-assembled In0.5Ga0.5As quantum dot, which show strong antibunching behaviour under both the conditions of cw and pulsed excitations. The calculated results are in agreement with the experimental measurements.

Published
2005

134. Nanoscale Optical Directional Coupler.

Author

Im, Song-Jin, Han, Yong-Ha, Ho, Kum-Song, Ri, Chol-Song, Ko, Yong-Hae, and Wang, Qu-Quan

Subjects
OPTICAL directional couplers, NANOELECTROMECHANICAL systems, NANOPHOTONIC integrated circuits, PLASMONICS, WAVEGUIDES, SIMULATION methods & models
Abstract

Ultracompact optical directional coupler is one of the key elements for nanoscale optical networks and highly integrated optical circuits. Although the transverse size has been reduced down to subwavelength by exploiting plasmonic waveguides, the longitudinal size has remained yet on the micrometer-scale, which seems to be a fundamental limitation by the conventional configuration based on cross-talk coupling between two neighboring waveguides. We have proposed a novel conception of optical directional coupler based on loss-overcompensated resonant coupling between two plasmonic waveguides via an in-between gain-assisted nanocavity. The loss-overcompensated state can be achieved by adjusting pumping rate in the nanocavity. The validity of the proposed conception is confirmed by numerical simulations of a physical model with the deep-subwavelength planar footprint of 300 nm × 300 nm, THz bandwidth, and an exceptionally low energy consumption on the order of 0.1 fJ per signal pulse. To our knowledge, it is the first proposed ultrafast nanoscale four-port directional coupler. [ABSTRACT FROM AUTHOR]

Published
2017
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135. A Z-Scan Study of LiNbO3 Thin Films

Author

Shi Jing, Qi-Kun Xue, Gong Qi-Huang, Liu Hai-lin, Wang Qu-Quan, Yang Bai-Feng, and Xiong Gui-guang

Subjects
Materials science, Morphology (linguistics), business.industry, Scanning electron microscope, General Physics and Astronomy, Nanoparticle, Carbon nanotube, Microstructure, Cathode, law.invention, Electric arc, Optics, law, Thin film, Composite material, business
Abstract

We have investigated the morphology and microstructure of carbon nanotubes and nanoparticles in cathode deposits prepared by self-sustained arc discharge. Scanning electron microscopy images indicate that there are two regions exhibiting different morphologies on the top surface of the cathode deposits. In the central region, there is a triangular pattern of spots with a diameter up to 100mum, which consists of carbon nanotubes and nanoparticles. In the fringe region, carbon nanotubes and nanoparticles are distributed randomly. In addition, carbon nanotubes in the central region have a larger inner diameter, compared with those in the fringe region. The outer diameter distribution of tubes in the central region is narrower than that of tubes in the fringe region, while the former has a smaller peak value than the latter. For the nanoparticles, they exhibit a different behaviour from the tubes existing in the same region. The difference between the microstructure of tubes or particles in the two regions is attributed to the different temperatures and temperature gradients during their formation.

Published
2002

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