The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman...The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. We find that the ultrashort pulses with about two optical cycles can be used to realize the population operation. This suggests that the population transfer can be completed in the femtosecond time scale. At the same time, our simulation shows that the signal of the carrier-envelope-phase-dependent effect can be enlarged due to quantum interference in some conditions. Our theoretic study may promote the research on the coherent control via ultrashort pulses in the related fields.展开更多
For the past thirty years, intense efforts have been made to record atomic scale movies that reveal the movement of atoms in molecules, the fast dynamical processes in biological tissues and cells, and the changes in ...For the past thirty years, intense efforts have been made to record atomic scale movies that reveal the movement of atoms in molecules, the fast dynamical processes in biological tissues and cells, and the changes in the structure of a solid confined to nano-scale volumes. A combination of sub-nanometer spatial resolution with picosecond or even femtosecond temporal resolution is required for such atomic movies. Additional important information can be obtained when the energy of the electron beam transmitted through the sample is measured. The four dimensional (4D) spatially and temporally resolved ultrafast electron microscopy method is made possible by the extremely high detection efficiency that is reached in 4D electron microscopy. Using ultra-short electron bunches for the visualization of biological tissue can also improve the spatial resolution compared to conventional electron microscopes, thereby enabling the study of complex biological samples of relevance to the life sciences. Of particular interest to a broad audience is the possibility to create a video, and in the future, a real atomic movie, using 4D electron tomography.展开更多
Coherent quantum effects have been confirmed for several biological processes. These processes exist in the environment of a warm wet cell where decoherence can be a serious concern. Here we propose a mechanism whereb...Coherent quantum effects have been confirmed for several biological processes. These processes exist in the environment of a warm wet cell where decoherence can be a serious concern. Here we propose a mechanism whereby quantum coherence may extend through the water matrix of a cell. The model is based on coherent waves of established ultrafast energy transfers in water. Computations based on the model are found to agree with several experimental results and numerical and descriptive predictions are presented. We compute wave speed, ~156 km/s, and wavelength, ~9.3 nm, and determine that these waves retain local coherence. Close agreements are found for the dipole moment of water dimers, results of microwave radiation on yeast, and the Kleiber law of metabolic rates. The theory requires that a spherical cell must have a minimum diameter of ~20 nm to accommodate a standing energy wave. The quantum properties of the modelsuggest that cellular chemistry favors reactions that support perpetuation of the energy waves.展开更多
In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler（CM-LPGC）.Temporal rectangular waveform with 2-ps full width at half maximum（FWHM） is obtained by tran...In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler（CM-LPGC）.Temporal rectangular waveform with 2-ps full width at half maximum（FWHM） is obtained by transforming the input Gaussian pulse.Tolerances of the CM-LPGC-based shaper to various non-ideal excitation conditions and fabricating errors are investigated.Results confirm that CM-LPGC is stable and suitable for optical pulse shaping operation.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61008016)the Natural Science Foundation in Shaanxi Province,China(Grant No.2010JQ1002)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20106101120020)
文摘The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. We find that the ultrashort pulses with about two optical cycles can be used to realize the population operation. This suggests that the population transfer can be completed in the femtosecond time scale. At the same time, our simulation shows that the signal of the carrier-envelope-phase-dependent effect can be enlarged due to quantum interference in some conditions. Our theoretic study may promote the research on the coherent control via ultrashort pulses in the related fields.
文摘For the past thirty years, intense efforts have been made to record atomic scale movies that reveal the movement of atoms in molecules, the fast dynamical processes in biological tissues and cells, and the changes in the structure of a solid confined to nano-scale volumes. A combination of sub-nanometer spatial resolution with picosecond or even femtosecond temporal resolution is required for such atomic movies. Additional important information can be obtained when the energy of the electron beam transmitted through the sample is measured. The four dimensional (4D) spatially and temporally resolved ultrafast electron microscopy method is made possible by the extremely high detection efficiency that is reached in 4D electron microscopy. Using ultra-short electron bunches for the visualization of biological tissue can also improve the spatial resolution compared to conventional electron microscopes, thereby enabling the study of complex biological samples of relevance to the life sciences. Of particular interest to a broad audience is the possibility to create a video, and in the future, a real atomic movie, using 4D electron tomography.
文摘Coherent quantum effects have been confirmed for several biological processes. These processes exist in the environment of a warm wet cell where decoherence can be a serious concern. Here we propose a mechanism whereby quantum coherence may extend through the water matrix of a cell. The model is based on coherent waves of established ultrafast energy transfers in water. Computations based on the model are found to agree with several experimental results and numerical and descriptive predictions are presented. We compute wave speed, ~156 km/s, and wavelength, ~9.3 nm, and determine that these waves retain local coherence. Close agreements are found for the dipole moment of water dimers, results of microwave radiation on yeast, and the Kleiber law of metabolic rates. The theory requires that a spherical cell must have a minimum diameter of ~20 nm to accommodate a standing energy wave. The quantum properties of the modelsuggest that cellular chemistry favors reactions that support perpetuation of the energy waves.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61007007 and 61101110)the Foundation of Beijing Municipal Committee of CPC Organization Department (Grant No. 2012D005002000001)
文摘In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler（CM-LPGC）.Temporal rectangular waveform with 2-ps full width at half maximum（FWHM） is obtained by transforming the input Gaussian pulse.Tolerances of the CM-LPGC-based shaper to various non-ideal excitation conditions and fabricating errors are investigated.Results confirm that CM-LPGC is stable and suitable for optical pulse shaping operation.
