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1.
准相位匹配级联二阶非线性全光波长转换研究   总被引:5,自引:2,他引:3  
对基于级联和频差频非线性效应铌酸锂光波导新型全光波长转换器进行了理论研究。这种新型波长变换器需要两束抽运光源,它将输入的抽运光波长置于信号光波段窗口的两边,抽运光波长与信号光波长相近容易实现最佳耦合又不会占用信号波段,而且具有偏振不敏感的优点。从建立级联和频差频铌酸锂光波导全光波长转换器的理论模型出发,给出了波导中光相互作用的耦合模方程;利用逐步法详细推导了耦合模方程的解,得出了物理意义清晰的转换光功率表达式,分析了非线性晶体相互作用长度、抽运光功率对转换效率的影响,为级联和频差频铌酸锂光波导全光波长转换器优化设计提供了理论依据。  相似文献
2.
30W级第二代钠信标激光器研究   总被引:1,自引:0,他引:1  
采用Nd∶YAG 1064与1319 nm激光在非线性晶体LBO中和频,获得了高功率、高光束质量、窄线宽的准连续微秒脉冲钠信标激光。该钠信标激光平均输出功率为33 W,光束质量因子M2=1.25,线宽小于0.4 GHz,波长为589 nm,并可精确调控到钠原子D2谱线,稳定性优于±0.3 GHz,重复频率为500 Hz,脉冲宽度约为120μs。与连续波钠信标激光相比,准连续微秒脉冲钠信标激光提供了门脉冲选通机制,可消除大气瑞利散射干扰和减小钠导引星像斑拉长现象,从而使自适应光学系统能够实现更好的校正效果,被称为第二代纳信标激光。基于此第二代钠信标激光器,在云南1.8 m口径望远镜上进行了外场试验,观测到激光钠导引星。  相似文献
3.
We present an experiment where mid-infrared radiation is detected indirectly via the second-order non-linear process of sum frequency generation. The mid-infrared sources used for the experiment are quantum cascade lasers, and we use a pump wavelength that yields an up-converted wavelength within the detection window of Silicon avalanche photo diodes. Compared with direct detection using state-of-the-art mid-infrared semiconductor detectors, the detection scheme we propose in this paper has the advantages of greater bandwidth and lower noise equivalent power.  相似文献
4.
Optical sum-frequency generation (SFG) is used to characterize CO stretching vibrations on Pt(111) and Pt(110) surfaces. Different adsorption sites (terminal, bridge and step sites) are identified in the SFG spectra of CO on Pt(111), in good quantitative agreement with previous infrared reflection-absorption experiments on this system. For CO on Pt(110) we only observe CO molecules on terminal sites. The measured CO stretching vibration frequencies on Pt(110), both for low and high coverages, are at variance with the results of previous infrared studies. Our SFG results for CO on Pt(110) are confirmed by independent EELS measurements which, in addition, also reveal the frustrated rotational mode and the metal-CO vibration. The measured frequency of 2065 cm−1 for low CO coverage on Pt(110)-(1 × 2) is consistent with a previously proposed empirical relation between the frequency of an isolated adsorbed CO molecule and the coordination number of the binding Pt surface atom.  相似文献
5.
The effect of varying effective index and random deviations of domain boundary on sum frequency generation (SFG) in quasi-phase-matching waveguides are analyzed and analytical expressions of the conversion efficiency are provided for the first time to our knowledge. By simplifying the coupled equations of SFG in waveguide, we provide analytical expressions of the conversion efficiency for the first time. Four models for variations of effective index and random errors of domains are investigated. The results demonstrate that, when effective index varying regularly along the waveguide, the normalized conversion efficiency of SFG is reduced and the curves of are no longer sinc2 function but ripple profiles, which is different from the situation in bulk crystals; with the same magnitude, random period error is of much more significance than random duty cycle error, which is similar with the case in bulk crystals.  相似文献
6.
Recently, thiocyanate groups were successfully used as precursors for thiolate assemblies. Indeed, they provide a useful alternative to thiol groups for self-assembly on metallic substrates. In order to check the adsorption properties and the quality of the thiocyanate-based self-assembled monolayers (SAMs), we use sum-frequency generation spectroscopy (SFG) and apply it to characterize the ad-layers of two similar molecules: decanethiol (DT) and decyl thiocyanate (DTCN) adsorbed on platinum surfaces. By comparing the SFG signals of the methyl and methylene vibration modes, we show that DTCN SAMs are less ordered than DT ones. These effects are related to the SAMs quality which depends on the molecular packing as highlighted by scanning tunnelling microscopy and X-ray photoelectron spectroscopy.  相似文献
7.
The effect of polymers weakly adsorbed on a quartz surface on the structure of the interfacial water molecules was investigated by optical sum frequency (SF) spectroscopy. As polymers, poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and two types of tri-block copolymer of Pluronic L64 and 17R-4 were used. SF intensity spectra of OH stretching mode of water molecules at the interface between a quartz substrate and aqueous solutions of the polymers were measured. The total SF intensity of the interfacial water of the L64 aqueous solution was smaller than those of other solutions. This result indicates that the L64 aqueous solution has smaller number of oriented interfacial water molecules. It is suggested that the rapid motion of hydrophilic parts of the adsorbed L64 disturbs the average orientation of the interfacial water molecules. On the other hand, the SF intensity from the interfacial water molecules of aqueous solutions with high ion strength did not depend on the species of the polymers in the solutions. The latter result suggests that the hydration of ions determines the structure of the interfacial water molecules.  相似文献
8.
Efficient generation of continuous-wave (CW) tunable light in the yellow region is reported. The method is based on sum-frequency mixing of a tunable Cr4+:forsterite laser with a Nd:YVO4 laser. A periodically poled lithium niobate crystal was placed intra-cavity in a Nd:YVO4 laser, and the Cr4+:forsterite laser was single-passed through the non-linear media. With this setup, it was possible to generate up to 3 mW of yellow light smoothly tunable from 573 to 587 nm. This is the highest output demonstrated to date for a tunable diode pumped solid-state CW laser in this wavelength region. The ways to improve the efficiency further are discussed.  相似文献
9.
Intra-cavity nonlinear frequency mixing in a diode-pumped, broadband Yb-doped fibre laser has been investigated. Second-harmonic generation of the fibre output, second-harmonic generation of the residual pump beam and sum frequency mixing between the two was achieved simultaneously, resulting in three colour operation in the blue-green region. Including the nonlinear crystal inside the cavity is also shown to be effective in reducing fluctuations in the output power.  相似文献
10.
Structural changes that occur on Pd-Nb2O5/Cu3Au(1 0 0) model catalysts upon thermal annealing were followed by sum frequency generation (SFG) and temperature-programmed desorption (TPD) using CO as probe molecule. SFG experiments were performed both under ultrahigh vacuum and mbar pressure. Heating the catalyst to temperatures above 300 K lead to an irreversible 50% decrease in the CO adsorption capacity and modified the remaining adsorption sites. Alterations of the phase between resonant and non-resonant SFG signals upon annealing indicate a change in the electronic structure of the surface, which excludes Pd sintering or migration of Nb2O5 over Pd particles to cause the observed effect and rather suggests the formation of “mixed Pd-NbOx” sites. The same changes in surface properties also occur during CO hydrogenation at 1 bar and high temperature, pointing to an involvement of “mixed Pd-NbOx” sites in catalytic reactions.  相似文献
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