We calculate the electronic structure and optical properties of F-doped anatase TiO2. The results indicate that the band gap ofF-doped TiO2 increases slightly compared with the pure TiO2. However, it is interesting th...We calculate the electronic structure and optical properties of F-doped anatase TiO2. The results indicate that the band gap ofF-doped TiO2 increases slightly compared with the pure TiO2. However, it is interesting that the visible absorption of F-doped TiO2 located between 600 and 700 nm is observed, and it enhances gradually with the increasing F concentration. Furthermore, according to the results of densities of states and imaginary part of dielectric function ε2（ω）, we propose that the transition between Ti 3d and Ti 3d states may be responsible for the visible absorption, but not the band gap narrowing.展开更多
A Schrodinger equation is solved numerically for a barrier in a quantum well and a quantum well in another well structure by the transfer matrix technique. Effect of structure parameters on the transmission probabilit...A Schrodinger equation is solved numerically for a barrier in a quantum well and a quantum well in another well structure by the transfer matrix technique. Effect of structure parameters on the transmission probabilities is investigated in detail. The results suggest that symmetry plays an important role in the coupling effect between the quantum wells. The relationship between the width of the inner well and the resonant energy levels in well-in- well structures is also studied. It is found that the ground state energy and the second resonant energy decrease with increasing width of the inner well, while the first resonant energy remains constant.展开更多
The third-order nonlinear optical properties of water-soluble Cu Se nanocrystals are studied in the near infrared range of 700-980 nm using a femtosecond pulsed laser by the Z-scan technique. It is observed that the n...The third-order nonlinear optical properties of water-soluble Cu Se nanocrystals are studied in the near infrared range of 700-980 nm using a femtosecond pulsed laser by the Z-scan technique. It is observed that the nonlinear optical response of Cu Se nanocrystals is sensitively dependent on the excitation wavelength and exhibits the enhanced nonlinearity compared with other selenides such as ZnSe and CdSe. The W-shaped Z-scan trace, a mixture of the reversed saturated absorption and saturated absorption, is observed near the plasmon resonance band of Cu Se nanocrystals, which is attributed to the state-filling of free carriers generated by copper vacancies (self-doping effect) of Cu Se nanocrystals as well as the hot carrier thermal effect upon intense femtosecond laser excitation. The large nonlinear optical response and tunable plasmonic band make Cu Se nanocrystals promising materials for applications in ultra-fast all-optical switching devices as well as nonlinear nanosensors.展开更多
基金Supported by the Natural Science Foundation of Tianjin(09JCYBJC04100,08JCYBJC14800)Science and TechnologyPlan Projects of the Ministry of Construction of China(2008-K7-10)Chinese National Key Basic Research Special Fund(2010CB933801)~~
基金Supported by the Specialized Research Fund for the Doctoral Program （SRFDP） of Higher Education State Education Ministry under Grant No 200800231058, the National Natural Science Foundation of China under Grant No 10947180, and the Natural Science Foundation of Tianjin （09JCYBJC04100）.
文摘We calculate the electronic structure and optical properties of F-doped anatase TiO2. The results indicate that the band gap ofF-doped TiO2 increases slightly compared with the pure TiO2. However, it is interesting that the visible absorption of F-doped TiO2 located between 600 and 700 nm is observed, and it enhances gradually with the increasing F concentration. Furthermore, according to the results of densities of states and imaginary part of dielectric function ε2（ω）, we propose that the transition between Ti 3d and Ti 3d states may be responsible for the visible absorption, but not the band gap narrowing.
基金Supported by the Natural Science Foundation of Tianjin （08JCYBJC14800）, the National Natural Science Foundation of China under Grant No 60476042, the National High-Tech Research and Development Programme of China under Grant No 2006AA03Z413, and the National Basic Research Programme of China under Grant No 2006CB921703.
文摘A Schrodinger equation is solved numerically for a barrier in a quantum well and a quantum well in another well structure by the transfer matrix technique. Effect of structure parameters on the transmission probabilities is investigated in detail. The results suggest that symmetry plays an important role in the coupling effect between the quantum wells. The relationship between the width of the inner well and the resonant energy levels in well-in- well structures is also studied. It is found that the ground state energy and the second resonant energy decrease with increasing width of the inner well, while the first resonant energy remains constant.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274302,11474276 and 11674240
文摘The third-order nonlinear optical properties of water-soluble Cu Se nanocrystals are studied in the near infrared range of 700-980 nm using a femtosecond pulsed laser by the Z-scan technique. It is observed that the nonlinear optical response of Cu Se nanocrystals is sensitively dependent on the excitation wavelength and exhibits the enhanced nonlinearity compared with other selenides such as ZnSe and CdSe. The W-shaped Z-scan trace, a mixture of the reversed saturated absorption and saturated absorption, is observed near the plasmon resonance band of Cu Se nanocrystals, which is attributed to the state-filling of free carriers generated by copper vacancies (self-doping effect) of Cu Se nanocrystals as well as the hot carrier thermal effect upon intense femtosecond laser excitation. The large nonlinear optical response and tunable plasmonic band make Cu Se nanocrystals promising materials for applications in ultra-fast all-optical switching devices as well as nonlinear nanosensors.
