We use the relative phase difference of two bichromatic fields of equal frequency differences for the coherent control of spontaneous emission of a three-level atom in the A configuration, diffects such as selective a...We use the relative phase difference of two bichromatic fields of equal frequency differences for the coherent control of spontaneous emission of a three-level atom in the A configuration, diffects such as selective and total cancellation of fluorescence decay are obtained simply by varying the phase difference. The phese dependence of fluorescence spectra is attributed to the fact that the four different field components induce the transitions in a closed loop configuratiou.展开更多
Planar polymer multi-model waveguides doped with Ag nano-particles and rhodamine B are fabricated and investigated by the spectroscopy analysis method as well as the M-line method. Experimental results shown that fluo...Planar polymer multi-model waveguides doped with Ag nano-particles and rhodamine B are fabricated and investigated by the spectroscopy analysis method as well as the M-line method. Experimental results shown that fluorescence enhancement occurs when excited by a wide band wavelength with Ag nano-particle concentration at a certain level. The maximum enhancement factor in our experiment is obtained to be about 3.8 when excited by 350 nm. Our study may have potential applications in polymers optical elements, such as polymer waveguide lasers and amplifiers.展开更多
Chemical oxidation is used to induce superconductivity in La2CuO4 expitaxial thin films fabricated by pulsed laser deposition technique. Details about the influence of oxidation time on structural, surface morphology,...Chemical oxidation is used to induce superconductivity in La2CuO4 expitaxial thin films fabricated by pulsed laser deposition technique. Details about the influence of oxidation time on structural, surface morphology, Raman spectra, and electrical properties have been investigated. The results convince that successful uptake of oxygen occurs in the oxidized films, and the content of the inserted oxygen increases with increasing oxidation interval. The possible mechanism for the excess oxygen insertion into the film is also discussed.展开更多
Employing the technique of symmetry reduction of analytic method, we solve the Ginzburg-Landau equation with varying nonlinear, dispersion, gain coefficients, and gain dispersion which originates from the limiting eff...Employing the technique of symmetry reduction of analytic method, we solve the Ginzburg-Landau equation with varying nonlinear, dispersion, gain coefficients, and gain dispersion which originates from the limiting effect of transition bandwidth in the realistic doped fibres. The parabolic asymptotic self-similar analytical solutions in gain medium of the normal GVD is found for the first time to our best knowledge. The evolution of pulse amplitude, strict linear phase chirp and effective temporal width are given with self-similarity results in longitudinal nonlinearity distribution and longitudinal gain fibre. These analytical solutions are in good agreement with the numerical simulations. Furthermore, we theoretically prove that pulse evolution has the characteristics of parabolic asymptotic self-similarity in doped ions dipole gain fibres.展开更多
Electric field enhancement distributions encountered in feed gap of opposing bi-Au cone-tips is studied using a frequency-domain three-dimensional finite element method to solve Maxwell＇s equations of electric field ...Electric field enhancement distributions encountered in feed gap of opposing bi-Au cone-tips is studied using a frequency-domain three-dimensional finite element method to solve Maxwell＇s equations of electric field distributions. Both the influences of cone-tip length and surrounding medium on electric field enhancement are investigated. The maximal enhancement value is discussed in terms of a simple physical model based on a standing wave on the tip surface associated with the antenna effect and surface plasmon. Simulated results demonstrate the enhancement is sensitive to the tip length. By selecting a suitably matched scale according to the incident wavelength, a large enhancement value can be observed within a small focused spot between the opposing tips permitting a high spatial resolution. The relative position of the opposing tips is also found for the optimum enhancement. All of the results suggest that our configuration is suitable for the site-specific Raman spectroscopic analysis at nanoscale.展开更多
We report ultrafast third-order nonlinear optical （NLO） properties of several chalcogenide glasses GeSx （x = 1.8, 2.0, 2.5） measured by femtosecond time-resolved optical Kerr gate technique at 82Ohm. The third-ord...We report ultrafast third-order nonlinear optical （NLO） properties of several chalcogenide glasses GeSx （x = 1.8, 2.0, 2.5） measured by femtosecond time-resolved optical Kerr gate technique at 82Ohm. The third-order nonlinear susceptibility of GeS1.8 glass is determined to be as large as 1.41 ×10^-12 esu, which is the maximum value of the third order nonlinear susceptibility Х^（3） for the three compositions investigated. The symmetric Gauss profiles of optical Kerr signals reveal the nature of ultrafast nonlinear response of these samples, which are originated from the ultrafast polarization of the electron clouds. By detailed microstructural analysis of these glasses based on the chain-crossing model （CCM） and the random-covalent-network model （RCNM）, it can be concluded that Х^（3） value of GeSx glasses can be enhanced greatly by S-S covalent bonds or S3 Ge-GeS3 ethane-l＆e units.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 60378008 and 10574052.
文摘We use the relative phase difference of two bichromatic fields of equal frequency differences for the coherent control of spontaneous emission of a three-level atom in the A configuration, diffects such as selective and total cancellation of fluorescence decay are obtained simply by varying the phase difference. The phese dependence of fluorescence spectra is attributed to the fact that the four different field components induce the transitions in a closed loop configuratiou.
基金Supported by the National Natural Science Foundation of China under Grant No 10474093, the National Basic Research Programme of China under Grant No 2006CB302900, and the Special Funds for Major State Basic Research Programme of China under Grant No 2005CCA04200.
文摘Planar polymer multi-model waveguides doped with Ag nano-particles and rhodamine B are fabricated and investigated by the spectroscopy analysis method as well as the M-line method. Experimental results shown that fluorescence enhancement occurs when excited by a wide band wavelength with Ag nano-particle concentration at a certain level. The maximum enhancement factor in our experiment is obtained to be about 3.8 when excited by 350 nm. Our study may have potential applications in polymers optical elements, such as polymer waveguide lasers and amplifiers.
基金Support by the National Natural Science Foundation of China, the National Key Basic Research Programme of China, and the State Key Lab of New Ceramics and Fine Processes.
文摘Chemical oxidation is used to induce superconductivity in La2CuO4 expitaxial thin films fabricated by pulsed laser deposition technique. Details about the influence of oxidation time on structural, surface morphology, Raman spectra, and electrical properties have been investigated. The results convince that successful uptake of oxygen occurs in the oxidized films, and the content of the inserted oxygen increases with increasing oxidation interval. The possible mechanism for the excess oxygen insertion into the film is also discussed.
基金Supported by the Natural Science Foundation of Guangdong Province under Grant No 04010397.
文摘Employing the technique of symmetry reduction of analytic method, we solve the Ginzburg-Landau equation with varying nonlinear, dispersion, gain coefficients, and gain dispersion which originates from the limiting effect of transition bandwidth in the realistic doped fibres. The parabolic asymptotic self-similar analytical solutions in gain medium of the normal GVD is found for the first time to our best knowledge. The evolution of pulse amplitude, strict linear phase chirp and effective temporal width are given with self-similarity results in longitudinal nonlinearity distribution and longitudinal gain fibre. These analytical solutions are in good agreement with the numerical simulations. Furthermore, we theoretically prove that pulse evolution has the characteristics of parabolic asymptotic self-similarity in doped ions dipole gain fibres.
基金Supported by National Natural Science Foundation of China under Grant Nos 30270367.
文摘Electric field enhancement distributions encountered in feed gap of opposing bi-Au cone-tips is studied using a frequency-domain three-dimensional finite element method to solve Maxwell＇s equations of electric field distributions. Both the influences of cone-tip length and surrounding medium on electric field enhancement are investigated. The maximal enhancement value is discussed in terms of a simple physical model based on a standing wave on the tip surface associated with the antenna effect and surface plasmon. Simulated results demonstrate the enhancement is sensitive to the tip length. By selecting a suitably matched scale according to the incident wavelength, a large enhancement value can be observed within a small focused spot between the opposing tips permitting a high spatial resolution. The relative position of the opposing tips is also found for the optimum enhancement. All of the results suggest that our configuration is suitable for the site-specific Raman spectroscopic analysis at nanoscale.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10504001, 10521002 and 50125205, the National Key Basic Research Programme of Chin under Grant No 2006CB806007, the 0pen Project Programme of Key Laboratory of Advanced Materials and Rheological Properties （Ministry of Education）, Xiangtan University, China.
文摘We report ultrafast third-order nonlinear optical （NLO） properties of several chalcogenide glasses GeSx （x = 1.8, 2.0, 2.5） measured by femtosecond time-resolved optical Kerr gate technique at 82Ohm. The third-order nonlinear susceptibility of GeS1.8 glass is determined to be as large as 1.41 ×10^-12 esu, which is the maximum value of the third order nonlinear susceptibility Х^（3） for the three compositions investigated. The symmetric Gauss profiles of optical Kerr signals reveal the nature of ultrafast nonlinear response of these samples, which are originated from the ultrafast polarization of the electron clouds. By detailed microstructural analysis of these glasses based on the chain-crossing model （CCM） and the random-covalent-network model （RCNM）, it can be concluded that Х^（3） value of GeSx glasses can be enhanced greatly by S-S covalent bonds or S3 Ge-GeS3 ethane-l＆e units.
