A high-sensitivity curvature sensor based on an up-taper-core-offset structure is proposed and demonstrated in this paper. Here two specially designed cascaded up-tapers with maximum diameters of 247 μm and 251 μm, ...A high-sensitivity curvature sensor based on an up-taper-core-offset structure is proposed and demonstrated in this paper. Here two specially designed cascaded up-tapers with maximum diameters of 247 μm and 251 μm, respectively, are used as a cladding mode exciting component. The excited cladding modes will propagate in the cladding and re-couplers with the core mode at the core-offset jointing point. When the curvature is changed, the dip wavelength of the sensor will shift to a blue wavelength and an average curvature sensitivity of more than -12.5 nm/m^-1 is achieved within the measured curvature intervals.展开更多
To break through the bottle-neck of quantum yield in upconversion （UC） core-shell system, we elucidated that the energy transfer efficiency in core-shell system had an evident contribution from the charge transfer o...To break through the bottle-neck of quantum yield in upconversion （UC） core-shell system, we elucidated that the energy transfer efficiency in core-shell system had an evident contribution from the charge transfer of interface with related to two factors： （i） band offsets and （2） binding energy area density. These two variables were determined by material intrinsic properties and core-shell thickness ratio. We further unraveled the mechanism of non-radiative energy transfer by charge transfer induced dipole at the inter- face, based on a quasi-classical derivation from F6rster type resonant energy transfer （FRET） model. With stable bonding across the interface, the contributions on energy transfer in both radiative and non-radiative energy transfer should also be accounted together in Auzel＇s energy transfer （ETU） model in core-shell system. Based on the discussion about interface bonding, band offsets, and forma- tion energies, we figured out the significance of interface bonding induced gap states （IBIGS） that played a significant role for influ- encing the charge transfer and radiative type energy transfer. The interface band offsets were a key factor in dominating the non-radiative energy transfer, which was also correlated to core-shell thickness ratio. We found that the energy area density with re- lated to core/shell thickness ratio followed the trend of Boltzman sigmoidal growth function. By the physical trend, this work contrib- uted a reference how the multi-layered core-shell structure was formed starting from the very beginning within minimum size. A route was paved towards a systematic study of the interface to unveil the energy transfer mechanism in core-shell systems.展开更多
The valence band offsets of the strained and longitudinally relaxed diamond/cubic boron-nitride （c-BN） （110） superlattice are investigated by the plane wave density functional theory approach and using the on-site...The valence band offsets of the strained and longitudinally relaxed diamond/cubic boron-nitride （c-BN） （110） superlattice are investigated by the plane wave density functional theory approach and using the on-site core electron as a reference energy level. For the strained diamond/c-BN superlattice, the valence band offset of around 1.50 eV is in good agreement with those using all the electrons methods. As for the longitudinally relaxed superlattice, the valence band offset of around 1.28 eV is smaller than that of the strained superlattice. The reason for this is mainly due to the split of the valence band maximum caused by the anisotropic strain.展开更多
文摘A high-sensitivity curvature sensor based on an up-taper-core-offset structure is proposed and demonstrated in this paper. Here two specially designed cascaded up-tapers with maximum diameters of 247 μm and 251 μm, respectively, are used as a cladding mode exciting component. The excited cladding modes will propagate in the cladding and re-couplers with the core mode at the core-offset jointing point. When the curvature is changed, the dip wavelength of the sensor will shift to a blue wavelength and an average curvature sensitivity of more than -12.5 nm/m^-1 is achieved within the measured curvature intervals.
基金Project supported by the National Natural Science Foundation of China(NSFC)(21425101,21321001,21371011,21331001)Ministry of Science and Technology(MOST)of China(2014CB643800)+3 种基金Natural Science Foundation of China(NSFC) for the Youth Scientist grant(11504309)the Initial Start-up Grant Support from the Department General Research Fund(Dept.GRF) from ABCT in the Hong Kong Polytechnic Universitythe Early Career Scheme(ECS) Fund(PolyU 253026/16P) from the Research Grant Council(RGC)in Hong Kongthe High Performance Supercomputer(ATOM Project)in PolyU
文摘To break through the bottle-neck of quantum yield in upconversion （UC） core-shell system, we elucidated that the energy transfer efficiency in core-shell system had an evident contribution from the charge transfer of interface with related to two factors： （i） band offsets and （2） binding energy area density. These two variables were determined by material intrinsic properties and core-shell thickness ratio. We further unraveled the mechanism of non-radiative energy transfer by charge transfer induced dipole at the inter- face, based on a quasi-classical derivation from F6rster type resonant energy transfer （FRET） model. With stable bonding across the interface, the contributions on energy transfer in both radiative and non-radiative energy transfer should also be accounted together in Auzel＇s energy transfer （ETU） model in core-shell system. Based on the discussion about interface bonding, band offsets, and forma- tion energies, we figured out the significance of interface bonding induced gap states （IBIGS） that played a significant role for influ- encing the charge transfer and radiative type energy transfer. The interface band offsets were a key factor in dominating the non-radiative energy transfer, which was also correlated to core-shell thickness ratio. We found that the energy area density with re- lated to core/shell thickness ratio followed the trend of Boltzman sigmoidal growth function. By the physical trend, this work contrib- uted a reference how the multi-layered core-shell structure was formed starting from the very beginning within minimum size. A route was paved towards a systematic study of the interface to unveil the energy transfer mechanism in core-shell systems.
基金supported by the National Natural Science Foundation of China (Grant No.60877017)the Innovation Program of Shanghai Municipal Education Commission (Grant No.08YZ04)the Shanghai Leading Academic Discipline Project (Grant No.S30107)
文摘The valence band offsets of the strained and longitudinally relaxed diamond/cubic boron-nitride （c-BN） （110） superlattice are investigated by the plane wave density functional theory approach and using the on-site core electron as a reference energy level. For the strained diamond/c-BN superlattice, the valence band offset of around 1.50 eV is in good agreement with those using all the electrons methods. As for the longitudinally relaxed superlattice, the valence band offset of around 1.28 eV is smaller than that of the strained superlattice. The reason for this is mainly due to the split of the valence band maximum caused by the anisotropic strain.
