wang yue - Academia.edu (original) (raw)
Papers by wang yue
Optics Communications, 2009
Discrete fractional Hadamard transform (DFrHaT) is a generalization of the Hadamard transform, wh... more Discrete fractional Hadamard transform (DFrHaT) is a generalization of the Hadamard transform, which has been widely used in signal processing. In this paper, we present the multiple-parameter discrete fractional Hadamard transform (MPDFrHaT), which has multiple order parameters instead of only one in DFrHaT. The proposed MPDFrHaT is shown to possess all of the desired properties of DFrHaT. In fact, it
Physical Review B, 1999
Low-temperature high-magnetic-field far-infrared spectroscopy and electron-spin-resonance measure... more Low-temperature high-magnetic-field far-infrared spectroscopy and electron-spin-resonance measurements have been performed on single crystals of the cubic perovskite KNiF 3. We found the absorption at 48.7 Ϯ0.3 cm Ϫ1 observed by Richards ͓P. L. Richards, J. Appl. Phys. 34, 1237 ͑1963͔͒ that was attributed to antiferromagnetic resonance ͑AFMR͒ is not magnetic in origin. Instead, a different absorption is well fit by a theory of AFMR with uniaxial anisotropy. Analysis yields an anisotropy energy of 8.7ϫ10 Ϫ3 cm Ϫ1. The ratio between the anisotropy field and the exchange field is 2.4ϫ10 Ϫ5. Thus, KNiF 3 is an excellent example of a Heisenberg antiferromagnet. ͓S0163-1829͑99͒00209-X͔
The Journal of Physical Chemistry C, 2009
Aligned bundles of conducting polymer nanowires are generated in situ during the polymerization o... more Aligned bundles of conducting polymer nanowires are generated in situ during the polymerization of o-anisidine. The presence of an appropriate initiator, a prolonged reaction time, and careful tuning of reaction conditions are crucial parameters for producing aligned nanowires. Mechanistic studies suggest hydrogen bonding between the substituents on the monomer and the polymer backbone is important for promoting alignment.
Solid State Communications, 2009
Co-doped ZnO diluted magnetic semiconductor films were prepared on Si(100) substrates by magnetro... more Co-doped ZnO diluted magnetic semiconductor films were prepared on Si(100) substrates by magnetron sputtering system and the Co content varies from 0.01 to 0.15. The X-ray diffraction results showed ZnO of the wurtzite structure. The ferromagnetism was observed at room temperature. The X-ray near-edge absorption spectroscopy revealed that Co substitutes for Zn 2+ ions in the valence of +2 state in the Co-doped ZnO films.
Solid State Communications, 2011
n multilayers with different Co thickness have been deposited on a silicon (Si) substrate to obta... more n multilayers with different Co thickness have been deposited on a silicon (Si) substrate to obtain better perpendicular anisotropy. The 0.5 nm thickness of the Co layer was chosen as the optimized thickness of the multilayer. Magnetic nanostructures with cap configuration were fabricated based on the template of polystyrene (PS) colloid sphere arrays with various curvature radius. Compared to the flat multilayer, the cap multilayer showed an oblique average anisotropy axis. When the curvature radius of the colloidal sphere increased, the shape of the multilayers changed from ellipsoidal to spherical, which led to a different dependence of magnetic properties on the field angles. The varying shape anisotropy, the dipole-dipole interaction between small magnetic caps, and the special nucleation mechanism on the spheres larger than 400 nm caused the M r /M s ratio and the coercivity to first increase and then decrease with varying curvature radius of the PS spheres.
Physical Review Letters, 2006
We report a comprehensive infrared magnetospectroscopy study of a CeRu 4 Sb 12 compound revealing... more We report a comprehensive infrared magnetospectroscopy study of a CeRu 4 Sb 12 compound revealing quasiparticles with a heavy effective mass m , with a detailed analysis of optical constants in fields up to 17 T. We find that the applied magnetic field strongly affects the low-energy excitations in the system. In particular, the magnitude of m ' 70 m b (m b is the quasiparticle band mass) at 10 K is suppressed by as much as 25% at 17 T. This effect is in quantitative agreement with the mean-field solution of the periodic Anderson model augmented with a Zeeman term.
![Research paper thumbnail of Erratum: Infrared probe of the anomalous magnetotransport of highly oriented pyrolytic graphite in the extreme quantum limit [Phys. Rev. B 74, 195404 (2006)]](https://attachments.academia-assets.com/102987310/thumbnails/1.jpg)
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Physical Review B, 2009
We report magnetotransmission measurements on a series of La 2−x Sr x CuO 4 thin films. The measu... more We report magnetotransmission measurements on a series of La 2−x Sr x CuO 4 thin films. The measurements were performed in magnetic fields of 18 T, on films with doping levels of x = 0, 0.01, 0.03, 0.045, 0.06, 0.08, and 0.10. In addition, an optimally doped film ͑x = 0.16͒ was studied in magnetic fields up to 33 T, both above and below its superconducting critical temperature T c = 41 K. A combination of Gaussian and wavelet filtering was employed to improve the signal-to-noise ratio of the data. However, even after this procedure, we could not detect any field-induced changes of transmission in any of the studied samples. Our results therefore rule out a direct relation between intensity changes in mid-infrared charge excitations and a bosonic mode in the far infrared. We discuss these observations in the context of existing proposals regarding the nature of medium energy range excitations in the cuprates.
physica status solidi (a), 2010
A new Mn-based Heusler alloy Mn 2 CuAl has been synthesized by the melt-spinning method. It has a... more A new Mn-based Heusler alloy Mn 2 CuAl has been synthesized by the melt-spinning method. It has an ordered bcc structure and is a ferrimagnet with a saturation moment of 1.44 m B /f.u. at 5 K. The magnetization mainly comes from the contributions of the antiparallel aligned Mn spin moments. A compensation point is observed at 630 K, indicating the antiferromagnetism between the two Mn sublattices. The Curie temperature of the ribbons is 690 K. When heated to 740 K, the Mn 2 CuAl ribbons completely decompose to a mixture of a tetragonal phase and a Cu 9 Al 4 phase. ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1484 Z. Q. Feng et al.: Phase stability and magnetic properties of Heusler alloy Mn 2 CuAl ribbons physica s s p status solidi a
Optics Express, 2008
We propose a digital spectral separation (DSS) system and methods to extract spectral information... more We propose a digital spectral separation (DSS) system and methods to extract spectral information optimally from a weak multispectral signal such as in the bioluminescent imaging (BLI) studies. This system utilizes our newly invented spatially-translated spectral-image mixer (SSM), which consists of dichroic beam splitters, a mirror, and a DSS algorithm. The DSS approach overcomes the shortcomings of the data acquisition scheme used for the current BLI systems. Primarily, using our DSS scheme, spectral information will not be filtered out. Accordingly, truly parallel multi-spectral multi-view acquisition is enabled for the first time to minimize experimental time and optimize data quality. This approach also permits recovery of the bioluminescent signal time course, which is useful to study the kinetics of multiple bioluminescent probes using multi-spectral bioluminescence tomography (MSBT).
Optics Communications, 2010
In recent years, the chaos-based cryptographic algorithms have suggested some new and efficient w... more In recent years, the chaos-based cryptographic algorithms have suggested some new and efficient ways to develop secure image encryption techniques. In this paper, we propose a new approach for image encryption based on the multiple-parameter discrete fractional Fourier transform and chaotic logistic maps in order to meet the requirements of the secure image transmission. In the proposed image encryption scheme, the image is encrypted by juxtaposition of sections of the image in the multiple-parameter discrete fractional Fourier domains and the alignment of sections is determined by chaotic logistic maps. This method does not require the use of phase keys. The new method has been compared with several existing methods and shows comparable or superior robustness to blind decryption.
Optical Engineering, 1997
A vision-based finger motion tracking approach is presented to gather quantitative data about bre... more A vision-based finger motion tracking approach is presented to gather quantitative data about breast palpation for cancer detection, such as finger positions, search pattern and coverage area, and this approach is used to develop a prototype palpation training system. Special color markers are used as features of interest because in breast palpation the background of the image is the breast itself which is similar to the fingers in color. This color similarity can hinder the ability or efficiency of other feature extraction methods if real-time performance is required. To simplify the feature extraction process, color space transform is utilized instead of directly using the original RGB values of the image. Although the clinical environment will be well illuminated, normalization of color attributes is applied to compensate for minor changes in illumination. A neighbor search is employed to ensure real-time performance, and a three-finger pattern topology is checked for the extracted features to avoid any possible false features. After detecting the features in the images, 3-D positions of the color marked fingers are calculated using the stereo vision principle. Experimental results with the prototype training system are given to show the performance and effectiveness of the proposed approach. This approach is expected to significantly improve the training quality of breast palpation, thus increasing the detection rate and accuracy of breast cancer.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005
ABSTRACT Recently, the rare gas buffer has been used to deposit small metal clusters nondestructi... more ABSTRACT Recently, the rare gas buffer has been used to deposit small metal clusters nondestructively. It presents a promising method in synthesizing the nanostructured materials. To study the collision dynamics of metal clusters on the rare gas buffer, the deposition of low energy Cu6 clusters on Ar films was investigated by molecular dynamics simulation. It was found that below 20 eV/atom the Cu clusters deposited on an Ar substrate nondestructively, while they were fragmented on a Cu surface. We observed that after deposition the Cu cluster was expanded and lost the original symmetric structure first. Then the cluster atoms recombined and the free cluster symmetry was regained. We found the Ar environment, e.g. the interaction between Ar and Ar atoms and that between Ar and Cu atoms, in the impact area helps to confine the Cu cluster.
New Journal of Physics, 2010
We present the results of THz, infrared and magneto-optical measurements performed on graphite na... more We present the results of THz, infrared and magneto-optical measurements performed on graphite nanoplatelet films as a function of temperature (4.2-300 K) and magnetic field (0-17.5 T). An effective medium analysis of the low-energy spectral response indicates that the nanoplatelet material is well described by a Drude function plus two infrared absorption bands. Interestingly, the Drude plasma frequency (∼1675 cm −1) decreases slowly with temperature, whereas the carrier scattering rate (∼175 cm −1) is temperature independent. Furthermore, measurements in an applied magnetic field at 4.2 K show that a large portion of the Drude spectral weight is transferred to finite frequency features corresponding to various Landau-level transitions. Some of these transition energies scale as √ B, as expected for Dirac-like quasi-particles in graphene and observed in other graphene-like materials. Thus, our results are consistent with recent theoretical calculations indicating that the spectrum of multilayer graphene can be decomposed into subsystems effectively identical to monolayer or bilayer graphene.
Molecular Physics, 2011
ABSTRACT The melting temperature and behaviour of gold nanowire in a single-walled carbon nanotub... more ABSTRACT The melting temperature and behaviour of gold nanowire in a single-walled carbon nanotube (SWNT) were investigated in detail using molecular dynamics simulations. The results showed that the melting temperature of the enclosed Au nanowire is lower than its bulk counterpart and higher than that observed for free-standing ones. Different from the melting behaviour of freestanding Au nanowires, the melting of Au nanowires enclosed in SWNTs with tube diameters (D) in the range 1.08 nm < D < 2.09 nm investigated here was found to initiate from the centre layers. The predicted melting temperature and behaviour of gold nanowires in SWNTs were clearly shown to be dependent on the interaction between C and Au atoms. The interaction is helpful to further stabilize the structure of enclosed Au nanowires, in particular, the outermost layer.
Laser Physics, 2009
The GaInAsSb/AlGaAsSb double quantum well lasers with an emission wavelength 2.0 μm, using the se... more The GaInAsSb/AlGaAsSb double quantum well lasers with an emission wavelength 2.0 μm, using the separate-confinement asymmetric waveguide, have been designed and fabricated, showing high quantum efficiency and high power conversion efficiency at continuous-wave operation mode. The threshold current density of the device is as low as 92 A/cm2. The internal loss coefficient and the internal quantum efficiency are 1.0 cm−1 and 86.1%, respectively. The 35% maximum power conversion efficiency (PCE) and narrow far-field patterned were achieved.
Laser Physics, 2011
ABSTRACT 2.2 μm InGaAsSb/AlGaAsSb Sb-based type-I laser diodes (LDs) were fabricated, with cavity... more ABSTRACT 2.2 μm InGaAsSb/AlGaAsSb Sb-based type-I laser diodes (LDs) were fabricated, with cavity lengths of 1000 μm and stripe width of 150 μm. The high output performance was achieved with the threshold current density of the device is as low as 187 A/cm2, slope efficiency of 0.2 W/A, and vertical and parallel divergent angles ϑ⊥ = 42° and ϑ| = 10°, respectively. The continuous wave operating up to 320 mW at room temperature (RT) were achieved.
Laser Physics Letters, 2009
ABSTRACT We report a short-cavity fiber laser configured with a high-concentration erbium-doped f... more ABSTRACT We report a short-cavity fiber laser configured with a high-concentration erbium-doped fiber with stable singlefrequency output. The fiber laser utilized a fiber Bragg grating inscribed into a piece of polarization-maintaining optical fiber as the output coupler to ensure a stable single frequency laser output. The polarization-maintaining optical fiber used in the output coupler is intended to provide the linearly polarized singlefrequency laser output. The fiber laser had a maximum hundreds of micron-Watt level power output pumped by a fiber pigtailed laser diode working at 980 nm. Mode hopping phenomenon was eliminated in such a short-cavity fiber laser. Laser frequency stability less than 400 MHz over 10 minutes was obtained. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters, 2009
ABSTRACT We report an acousto-optic (AO) Q-switched fiber laser with linearly polarized short pul... more ABSTRACT We report an acousto-optic (AO) Q-switched fiber laser with linearly polarized short pulse output. The fiber laser was set up by applying a piece of large mode area polarization maintaining Yb fiber of 1 meter length as the gain medium and a free-space AO Q-switch as the modulating element. The fiber laser was pumped by a fiber pigtailed laser diode working at 976 nm. By suitably adjusting the distance between the AO Q-switch and the cavity mirror, stable Q-switched short pulse laser output was achieved with output power up to 10 W and repetition rate between 20 kHz and 50 kHz. The shortest pulse duration of 33 ns was achieved at repetition rate of 20 kHz when the output power reached about 10 W. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters, 2009
ABSTRACT We report experimental results on an all-fiberized linearly polarized single-mode pulse ... more ABSTRACT We report experimental results on an all-fiberized linearly polarized single-mode pulse Yb-doped fiber laser/amplifier working at 1064 nm. Using a fiberized acousto-optic Q-switched ytterbium fiber laser as the seed source, a double-clad polarization-maintaining fiber as the gain medium, a (6+1) × 1 multimode pump combiner to input the seed signal and the pump power, an Yb fiber master oscillator power amplifier (MOPA) is demonstrated. It delivers a linearly polarized pulsed laser output working at 1064 nm with an average power of 30 W, a repetition rate of 40 kHz, a pulse duration time about 30 ns, a polarization extinction ratio greater than 10 dB, and a beam quality factor (M2) of 1.36. Our experiments were pump-power limited and considerable scope remains for further power-scaling of such fiber MOPA using this approach. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Optics Communications, 2009
Discrete fractional Hadamard transform (DFrHaT) is a generalization of the Hadamard transform, wh... more Discrete fractional Hadamard transform (DFrHaT) is a generalization of the Hadamard transform, which has been widely used in signal processing. In this paper, we present the multiple-parameter discrete fractional Hadamard transform (MPDFrHaT), which has multiple order parameters instead of only one in DFrHaT. The proposed MPDFrHaT is shown to possess all of the desired properties of DFrHaT. In fact, it
Physical Review B, 1999
Low-temperature high-magnetic-field far-infrared spectroscopy and electron-spin-resonance measure... more Low-temperature high-magnetic-field far-infrared spectroscopy and electron-spin-resonance measurements have been performed on single crystals of the cubic perovskite KNiF 3. We found the absorption at 48.7 Ϯ0.3 cm Ϫ1 observed by Richards ͓P. L. Richards, J. Appl. Phys. 34, 1237 ͑1963͔͒ that was attributed to antiferromagnetic resonance ͑AFMR͒ is not magnetic in origin. Instead, a different absorption is well fit by a theory of AFMR with uniaxial anisotropy. Analysis yields an anisotropy energy of 8.7ϫ10 Ϫ3 cm Ϫ1. The ratio between the anisotropy field and the exchange field is 2.4ϫ10 Ϫ5. Thus, KNiF 3 is an excellent example of a Heisenberg antiferromagnet. ͓S0163-1829͑99͒00209-X͔
The Journal of Physical Chemistry C, 2009
Aligned bundles of conducting polymer nanowires are generated in situ during the polymerization o... more Aligned bundles of conducting polymer nanowires are generated in situ during the polymerization of o-anisidine. The presence of an appropriate initiator, a prolonged reaction time, and careful tuning of reaction conditions are crucial parameters for producing aligned nanowires. Mechanistic studies suggest hydrogen bonding between the substituents on the monomer and the polymer backbone is important for promoting alignment.
Solid State Communications, 2009
Co-doped ZnO diluted magnetic semiconductor films were prepared on Si(100) substrates by magnetro... more Co-doped ZnO diluted magnetic semiconductor films were prepared on Si(100) substrates by magnetron sputtering system and the Co content varies from 0.01 to 0.15. The X-ray diffraction results showed ZnO of the wurtzite structure. The ferromagnetism was observed at room temperature. The X-ray near-edge absorption spectroscopy revealed that Co substitutes for Zn 2+ ions in the valence of +2 state in the Co-doped ZnO films.
Solid State Communications, 2011
n multilayers with different Co thickness have been deposited on a silicon (Si) substrate to obta... more n multilayers with different Co thickness have been deposited on a silicon (Si) substrate to obtain better perpendicular anisotropy. The 0.5 nm thickness of the Co layer was chosen as the optimized thickness of the multilayer. Magnetic nanostructures with cap configuration were fabricated based on the template of polystyrene (PS) colloid sphere arrays with various curvature radius. Compared to the flat multilayer, the cap multilayer showed an oblique average anisotropy axis. When the curvature radius of the colloidal sphere increased, the shape of the multilayers changed from ellipsoidal to spherical, which led to a different dependence of magnetic properties on the field angles. The varying shape anisotropy, the dipole-dipole interaction between small magnetic caps, and the special nucleation mechanism on the spheres larger than 400 nm caused the M r /M s ratio and the coercivity to first increase and then decrease with varying curvature radius of the PS spheres.
Physical Review Letters, 2006
We report a comprehensive infrared magnetospectroscopy study of a CeRu 4 Sb 12 compound revealing... more We report a comprehensive infrared magnetospectroscopy study of a CeRu 4 Sb 12 compound revealing quasiparticles with a heavy effective mass m , with a detailed analysis of optical constants in fields up to 17 T. We find that the applied magnetic field strongly affects the low-energy excitations in the system. In particular, the magnitude of m ' 70 m b (m b is the quasiparticle band mass) at 10 K is suppressed by as much as 25% at 17 T. This effect is in quantitative agreement with the mean-field solution of the periodic Anderson model augmented with a Zeeman term.
Physical Review B, 2009
We report magnetotransmission measurements on a series of La 2−x Sr x CuO 4 thin films. The measu... more We report magnetotransmission measurements on a series of La 2−x Sr x CuO 4 thin films. The measurements were performed in magnetic fields of 18 T, on films with doping levels of x = 0, 0.01, 0.03, 0.045, 0.06, 0.08, and 0.10. In addition, an optimally doped film ͑x = 0.16͒ was studied in magnetic fields up to 33 T, both above and below its superconducting critical temperature T c = 41 K. A combination of Gaussian and wavelet filtering was employed to improve the signal-to-noise ratio of the data. However, even after this procedure, we could not detect any field-induced changes of transmission in any of the studied samples. Our results therefore rule out a direct relation between intensity changes in mid-infrared charge excitations and a bosonic mode in the far infrared. We discuss these observations in the context of existing proposals regarding the nature of medium energy range excitations in the cuprates.
physica status solidi (a), 2010
A new Mn-based Heusler alloy Mn 2 CuAl has been synthesized by the melt-spinning method. It has a... more A new Mn-based Heusler alloy Mn 2 CuAl has been synthesized by the melt-spinning method. It has an ordered bcc structure and is a ferrimagnet with a saturation moment of 1.44 m B /f.u. at 5 K. The magnetization mainly comes from the contributions of the antiparallel aligned Mn spin moments. A compensation point is observed at 630 K, indicating the antiferromagnetism between the two Mn sublattices. The Curie temperature of the ribbons is 690 K. When heated to 740 K, the Mn 2 CuAl ribbons completely decompose to a mixture of a tetragonal phase and a Cu 9 Al 4 phase. ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1484 Z. Q. Feng et al.: Phase stability and magnetic properties of Heusler alloy Mn 2 CuAl ribbons physica s s p status solidi a
Optics Express, 2008
We propose a digital spectral separation (DSS) system and methods to extract spectral information... more We propose a digital spectral separation (DSS) system and methods to extract spectral information optimally from a weak multispectral signal such as in the bioluminescent imaging (BLI) studies. This system utilizes our newly invented spatially-translated spectral-image mixer (SSM), which consists of dichroic beam splitters, a mirror, and a DSS algorithm. The DSS approach overcomes the shortcomings of the data acquisition scheme used for the current BLI systems. Primarily, using our DSS scheme, spectral information will not be filtered out. Accordingly, truly parallel multi-spectral multi-view acquisition is enabled for the first time to minimize experimental time and optimize data quality. This approach also permits recovery of the bioluminescent signal time course, which is useful to study the kinetics of multiple bioluminescent probes using multi-spectral bioluminescence tomography (MSBT).
Optics Communications, 2010
In recent years, the chaos-based cryptographic algorithms have suggested some new and efficient w... more In recent years, the chaos-based cryptographic algorithms have suggested some new and efficient ways to develop secure image encryption techniques. In this paper, we propose a new approach for image encryption based on the multiple-parameter discrete fractional Fourier transform and chaotic logistic maps in order to meet the requirements of the secure image transmission. In the proposed image encryption scheme, the image is encrypted by juxtaposition of sections of the image in the multiple-parameter discrete fractional Fourier domains and the alignment of sections is determined by chaotic logistic maps. This method does not require the use of phase keys. The new method has been compared with several existing methods and shows comparable or superior robustness to blind decryption.
Optical Engineering, 1997
A vision-based finger motion tracking approach is presented to gather quantitative data about bre... more A vision-based finger motion tracking approach is presented to gather quantitative data about breast palpation for cancer detection, such as finger positions, search pattern and coverage area, and this approach is used to develop a prototype palpation training system. Special color markers are used as features of interest because in breast palpation the background of the image is the breast itself which is similar to the fingers in color. This color similarity can hinder the ability or efficiency of other feature extraction methods if real-time performance is required. To simplify the feature extraction process, color space transform is utilized instead of directly using the original RGB values of the image. Although the clinical environment will be well illuminated, normalization of color attributes is applied to compensate for minor changes in illumination. A neighbor search is employed to ensure real-time performance, and a three-finger pattern topology is checked for the extracted features to avoid any possible false features. After detecting the features in the images, 3-D positions of the color marked fingers are calculated using the stereo vision principle. Experimental results with the prototype training system are given to show the performance and effectiveness of the proposed approach. This approach is expected to significantly improve the training quality of breast palpation, thus increasing the detection rate and accuracy of breast cancer.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005
ABSTRACT Recently, the rare gas buffer has been used to deposit small metal clusters nondestructi... more ABSTRACT Recently, the rare gas buffer has been used to deposit small metal clusters nondestructively. It presents a promising method in synthesizing the nanostructured materials. To study the collision dynamics of metal clusters on the rare gas buffer, the deposition of low energy Cu6 clusters on Ar films was investigated by molecular dynamics simulation. It was found that below 20 eV/atom the Cu clusters deposited on an Ar substrate nondestructively, while they were fragmented on a Cu surface. We observed that after deposition the Cu cluster was expanded and lost the original symmetric structure first. Then the cluster atoms recombined and the free cluster symmetry was regained. We found the Ar environment, e.g. the interaction between Ar and Ar atoms and that between Ar and Cu atoms, in the impact area helps to confine the Cu cluster.
New Journal of Physics, 2010
We present the results of THz, infrared and magneto-optical measurements performed on graphite na... more We present the results of THz, infrared and magneto-optical measurements performed on graphite nanoplatelet films as a function of temperature (4.2-300 K) and magnetic field (0-17.5 T). An effective medium analysis of the low-energy spectral response indicates that the nanoplatelet material is well described by a Drude function plus two infrared absorption bands. Interestingly, the Drude plasma frequency (∼1675 cm −1) decreases slowly with temperature, whereas the carrier scattering rate (∼175 cm −1) is temperature independent. Furthermore, measurements in an applied magnetic field at 4.2 K show that a large portion of the Drude spectral weight is transferred to finite frequency features corresponding to various Landau-level transitions. Some of these transition energies scale as √ B, as expected for Dirac-like quasi-particles in graphene and observed in other graphene-like materials. Thus, our results are consistent with recent theoretical calculations indicating that the spectrum of multilayer graphene can be decomposed into subsystems effectively identical to monolayer or bilayer graphene.
Molecular Physics, 2011
ABSTRACT The melting temperature and behaviour of gold nanowire in a single-walled carbon nanotub... more ABSTRACT The melting temperature and behaviour of gold nanowire in a single-walled carbon nanotube (SWNT) were investigated in detail using molecular dynamics simulations. The results showed that the melting temperature of the enclosed Au nanowire is lower than its bulk counterpart and higher than that observed for free-standing ones. Different from the melting behaviour of freestanding Au nanowires, the melting of Au nanowires enclosed in SWNTs with tube diameters (D) in the range 1.08 nm < D < 2.09 nm investigated here was found to initiate from the centre layers. The predicted melting temperature and behaviour of gold nanowires in SWNTs were clearly shown to be dependent on the interaction between C and Au atoms. The interaction is helpful to further stabilize the structure of enclosed Au nanowires, in particular, the outermost layer.
Laser Physics, 2009
The GaInAsSb/AlGaAsSb double quantum well lasers with an emission wavelength 2.0 μm, using the se... more The GaInAsSb/AlGaAsSb double quantum well lasers with an emission wavelength 2.0 μm, using the separate-confinement asymmetric waveguide, have been designed and fabricated, showing high quantum efficiency and high power conversion efficiency at continuous-wave operation mode. The threshold current density of the device is as low as 92 A/cm2. The internal loss coefficient and the internal quantum efficiency are 1.0 cm−1 and 86.1%, respectively. The 35% maximum power conversion efficiency (PCE) and narrow far-field patterned were achieved.
Laser Physics, 2011
ABSTRACT 2.2 μm InGaAsSb/AlGaAsSb Sb-based type-I laser diodes (LDs) were fabricated, with cavity... more ABSTRACT 2.2 μm InGaAsSb/AlGaAsSb Sb-based type-I laser diodes (LDs) were fabricated, with cavity lengths of 1000 μm and stripe width of 150 μm. The high output performance was achieved with the threshold current density of the device is as low as 187 A/cm2, slope efficiency of 0.2 W/A, and vertical and parallel divergent angles ϑ⊥ = 42° and ϑ| = 10°, respectively. The continuous wave operating up to 320 mW at room temperature (RT) were achieved.
Laser Physics Letters, 2009
ABSTRACT We report a short-cavity fiber laser configured with a high-concentration erbium-doped f... more ABSTRACT We report a short-cavity fiber laser configured with a high-concentration erbium-doped fiber with stable singlefrequency output. The fiber laser utilized a fiber Bragg grating inscribed into a piece of polarization-maintaining optical fiber as the output coupler to ensure a stable single frequency laser output. The polarization-maintaining optical fiber used in the output coupler is intended to provide the linearly polarized singlefrequency laser output. The fiber laser had a maximum hundreds of micron-Watt level power output pumped by a fiber pigtailed laser diode working at 980 nm. Mode hopping phenomenon was eliminated in such a short-cavity fiber laser. Laser frequency stability less than 400 MHz over 10 minutes was obtained. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters, 2009
ABSTRACT We report an acousto-optic (AO) Q-switched fiber laser with linearly polarized short pul... more ABSTRACT We report an acousto-optic (AO) Q-switched fiber laser with linearly polarized short pulse output. The fiber laser was set up by applying a piece of large mode area polarization maintaining Yb fiber of 1 meter length as the gain medium and a free-space AO Q-switch as the modulating element. The fiber laser was pumped by a fiber pigtailed laser diode working at 976 nm. By suitably adjusting the distance between the AO Q-switch and the cavity mirror, stable Q-switched short pulse laser output was achieved with output power up to 10 W and repetition rate between 20 kHz and 50 kHz. The shortest pulse duration of 33 ns was achieved at repetition rate of 20 kHz when the output power reached about 10 W. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters, 2009
ABSTRACT We report experimental results on an all-fiberized linearly polarized single-mode pulse ... more ABSTRACT We report experimental results on an all-fiberized linearly polarized single-mode pulse Yb-doped fiber laser/amplifier working at 1064 nm. Using a fiberized acousto-optic Q-switched ytterbium fiber laser as the seed source, a double-clad polarization-maintaining fiber as the gain medium, a (6+1) × 1 multimode pump combiner to input the seed signal and the pump power, an Yb fiber master oscillator power amplifier (MOPA) is demonstrated. It delivers a linearly polarized pulsed laser output working at 1064 nm with an average power of 30 W, a repetition rate of 40 kHz, a pulse duration time about 30 ns, a polarization extinction ratio greater than 10 dB, and a beam quality factor (M2) of 1.36. Our experiments were pump-power limited and considerable scope remains for further power-scaling of such fiber MOPA using this approach. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)