共查询到20条相似文献,搜索用时 15 毫秒
1.
采用基于遗传算法(Genetic algorithm)的自适应反馈系统,成功实现了二溴甲烷多个拉曼振动模式的选择激发.通过脉冲分析方法(二次谐波频率分辨光谱开关和二次谐波交叉频率分辨光谱开关)(SHG-FROG和SHG-XFROG),在时域和频域上对优化脉冲进行还原和分析,结果表明:空间光学调制器(SLM)将优化脉冲调制成具有负啾啁特性的脉冲串.该选择激发实验的成功实现验证了相干控制自适应系统在研究复杂分子系统方面具有良好的应用前景. 相似文献
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Masanari Okuno Hideaki Kano Philippe Leproux Vincent Couderc Hiro-o Hamaguchi 《Optical Fiber Technology》2012,18(5):388-393
We describe and characterize a multiplex CARS microspectroscopic system that uses a nanosecond supercontinuum generated from a photonic crystal fiber and a sub-nanosecond pulse laser. This system has a high spectral resolution (<0.1 cm?1) and an ultrabroadband spectral coverage (>2500 cm?1). The estimated spatial resolutions are 0.45 μm (lateral) and 4.5 μm (axial), respectively. This system enables us to obtain CARS spectra and corresponding images in the fingerprint region as well in the CH stretch region. Using this system, we have successfully obtained label-free and multi-mode vibrational images of a yeast cell. 相似文献
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ZHANG Hui CHANG Sheng-jiang ZHANG Yan-xin ZHAO Xiang-ting 《光电子快报》2008,4(2):103-105
A new method to obtain supercontinuum(SC) source for multiplex coherent anti-stokes Raman scattering (CARS) microscopy is proposed. The nonlinear propagation in photonic-crystal fibers (PCF) of femtosecond pulse laser with central wavelength at 800.9 nm is studied with scalar wave theory. Based on the incident laser power and dispersion of PCF, super broadband source for multiplex CARS microscopy is designed. 相似文献
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利用飞秒自适应脉冲整形相干控制技术成功实现了甲醇溶液中甲基对称(vS(CH3)2832cm-1)和反对称(VAS(CH3)2948cm-1)振动能级相干反斯托克斯拉曼光谱(CARS)的选择激发.为了进一步探究双光束飞秒CARS光谱实现选择激发的机制,采用二次谐波频率分辨光学开关(SHG-FROG)测量方法对整形前后的泵浦激光脉冲进行了探测. SHG-FROG痕迹结果显示裁剪泵浦光中的有效频段可实现飞秒CARS的选择激发.研究表明飞秒自适应脉冲整形相干控制技术对于复杂分子系统飞秒CARS的选择激发研究具有非常重要的科学意义. 相似文献
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We propose a new method for studying surface vibrational spectroscopy based on an extension of the picosecond stimulated Raman gain technique. This technique is extremely surface sensitive and can detect coverages of 1 percent of a monolayer. This technique does not require ultrahigh vacuums (as do electron spectroscopies), is an extremely sensitive probe of surface local fields, has very high frequency resolution (<1 cm-1) and very short time resolution (∼ 1 ps). 相似文献
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A convenient variation of Raman-induced Kerr effect spectroscopy (RIKES) which overcomes many of the previous limitations of coherent Raman spectroscopy is introduced. Quantum limited signal-to-noise ratios may be approached by the use of optical heterodyne detection (OHD). Detector current, linearly proportional and phase sensitive to the third-order nonlinear susceptibility, and linearly proportional to the Raman scattering cross section, is produced. Heterodyne detection in coherent Raman spectroscopy enables the detection of weak Raman signals that would otherwise be obscured by noise resulting from background sources. 相似文献
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Fano共振效应拥有独特的局域场增强效果,在表面增强相干反斯托克斯拉曼散射中,不同波长局域场增强空间位置相同的结构结合Fano共振效应,可以实现混合频率共振模式,使得表面增强相干反斯托克斯拉曼散射总的增强因子得到大幅度提高。采用FDTD软件系统研究了对称的交叉蝴蝶结Au纳米结构的Fano共振效应,该效应使得交叉蝴蝶结结构中心位置附近的电场强度得到大幅度的增强,把该结构应用到表面增强相干反斯托克斯拉曼散射中,可以使表面增强相干反斯托克斯拉曼散射信号的增强因子高达1013,达到单分子检测的水平。 相似文献
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Coherent anti-Stokes Raman scattering spectroscopy(CARS) is a well-known detecting tool in biosensing and nonlinear spectroscopy. It can provide a non-invasive alternative without the need for exogenous labels, while the enhancement factor for surface plasmon resonances(SPR) are extensively used to increase the local field close to the oscillators and which can obtain high enhancement. In this work, we investigate the enhancement factor of our structure for surface-enhanced coherent anti-Stokes Raman scattering. The absorption spectrum of the structure has been studied, a wide range of absorption has been realized. The enhancement can be as high as 1016 over standard CARS. Our design is very useful for improving the enhancement factor of surface-enhanced coherent anti-Stokes Raman scattering. 相似文献
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G. Bolognini S. Sugliani F. Di Pasquale 《Photonics Technology Letters, IEEE》2004,16(5):1286-1288
The impact of signal double Rayleigh scattering (DRS) noise in time-division multiplexed counterpropagating Raman pumping schemes is theoretically and experimentally investigated. We show that, for small pump modulation duty cycles, DRS noise can be greatly enhanced with respect to continuous-wave pumping. By increasing the pump modulation frequency, however, this detrimental effect is effectively reduced, providing a powerful technique for noise figure equalization and pump four-wave mixing suppression in large bandwidth discrete and distributed amplifiers. 相似文献
13.
Recrystallized silicon-on-oxide were analyzed by laser Raman scattering spectroscopy. By changing the excitation laser wavelength,
the in-depth stress profile was obtained. The in-depth stress change was strongly dependent on recrystallization power. Recrystallized
silicon structures were confirmed by cross sectional TEM observations. Dependent on recrystallization power, silicon film
structures changed from small grain or small and large two grain layers to continuous large grain films. 相似文献
14.
Amplified spontaneous Raman scattered light power in forward and backward Raman amplifiers is theoretically and experimentally studied under the assumption of the constant Raman gain coefficient in the bandwidth of an optical filter. On the basis of the results, the power ratio of the amplified signal to amplified spontaneous scattering is discussed. As a result, it is clarified that the effect of amplified spontaneous Raman scattering on the signal to noise ratio for backward Raman scattering is larger than for forward Raman scattering. 相似文献
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This experimental paper describes the operation of simple coherent laser-generated tunable source of medium power (1 to 104watts) in the visible spectrum (15 600 to 19 400 cm-1) with high repetition rate (1 to 20 pps). A broad-band source is created by aQ -switched Nd:YAG laser beam in a cell containing carbon disulphide, by a complex process involving multiple-order stimulated Raman scattering, self-focusing, and parametric line broadening. The spectrum of this source extends over more than 4000 wavenumbers in the infrared. It presents broad intensity peaks at distances from the laser line equal to multiples of the CS2 Raman shift, and an intense continuum. This source is selectively up-converted by the laser beam itself in a nonlinear lithium niobate crystal with both beams collinear. Temperature adjustment of the crystal acts on the phase-matching condition and provides continuous tuning from 0.515 μ at - 100° C to 0.640 μ at 375° C. The linewidth is less than 11 cm-1. This simple tunable source includes no critical components and does not put stringent requirements on crystal quality. The up-converter also provides a good experimental method for studying the IR spectra of pulsed sources. 相似文献
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Stimulated Raman scattering (SRS) from infrared-active phonons in quartz is discussed. The scattering is concluded to be from a different region ofk space than that previously stated in the literature. The possibility of producing a broadly tunable parametric oscillator via SRS in quartz is viewed with pessimism. 相似文献
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V. Lemos S. Guerini S.M. Lala L.A. Montoro J.M. Rosolen 《Microelectronics Journal》2005,36(11):1020-1022
The possibility of inserting lithium into single wall carbon nanotube bundles during the growth process is analyzed in this work by using the Raman technique as probe. The nanotubes were prepared by the arc discharge method by using catalysts prepared by mixing compounds containing lithium and as their counterpart, a similar mixture without this alkali-metal. The two pair of samples studied in this work were obtained with the following catalysts: (i) Li2CO3/NiO/CoO and NiO/CoO; or (ii) LiCo0.5Ni0.5O2 and Ni/Co. Raman spectra reveal that the tangential bands profiles of the samples prepared with the catalyst containing lithium is considerably modified in both cases. In the case of the carbon nanotubes obtained using the LiCo0.5Ni0.5O2 catalyst a down shift and severe broadening are observed in addition. Comparison of our results with those published previously for alkali-metals doped single wall carbon nanotubes allowed to conclude that lithium incorporation, actually, occurs during the growth process. 相似文献
18.
Hiroshi Harima 《Microelectronic Engineering》2006,83(1):126-129
Raman scattering is a powerful non-contact and non-destructive characterization tool for SiC polytypes for both the lattice and electronic properties. Here, I will briefly review two recent Raman experiments on SiC; metal/SiC interface reactions probed by visible lasers and ion-implantation damages probed by deep UV lasers. These studies utilize the opposite aspects of the probe laser, i.e. deep and shallow penetration depth into SiC. 相似文献
19.
The spectrum of amplified spontaneous Raman scattering and gain in a fiber Raman amplifer has been calculated analytically as a function of distance and pump power. The model used makes no assumptions on the magnitude of the gain and considers the pump nondepletion region. From the results, the on/off ratio has been calculated and is found to have a variation with length that depends on frequency detuning. An enhancement in on/off ratio is also found for small fiber lengths but at limited gain. The use of a narrow-bandpass optical fiber leads to quite different behavior of the on/off ratio than for the unfiltered case. 相似文献
20.
Jianglei Ma Weng Cho Chew Cai-Cheng Lu Jiming Song 《Antennas and Propagation, IEEE Transactions on》2000,48(6):860-867
Compared to the TM case, the inverse scattering problem for the TE incident field is more complicated due to its stronger nonlinearity. This work provides an effective method for the reconstruction of two-dimensional (2-D) inhomogeneous dielectric objects from TE scattering data. The algorithm applies the distorted Born iterative method to the integral equation of strong permittivity fluctuation to reconstruct scatterers with high-permittivity contrast. Numerical simulations are performed and the results show that the distorted Born iterative method (DBIM) for strong permittivity fluctuation (SPF-DBIM) converges faster and can obtain better reconstructions for objects with larger dimensions and higher contrasts in comparison with ordinary DBIM. A frequency hopping technique is also applied to further increase the contrast 相似文献