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使用分步傅里叶变换和四阶龙格库塔法(R-K) ,对高强度激光以Ⅰ/Ⅱ类角度失谐方式,在KDP晶体中的谐波转换进行了研究,详细讨论了离散效应对三次谐波转换的影响。结果表明,离散效应不但降低了三次谐波转换效率,而且使谐波光束质量显著降低;初始入射基频光束腰半径较小时,离散效应是二次谐波转换和三次谐波转换效率降低的主要因素,失谐角对三次谐波转换的影响较小;随着束腰半径的增加,离散效应的影响逐渐减小,失谐角对三次谐波转换的影响逐渐增加。 相似文献
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In this paper we revisit the third harmonic generation from a femtosecond laser filament in air and its significant enhancement (~ 100 times) with a intercepting pump pulse, which has been reported very recently. The enhanced third harmonic is studied as a function of the pulse polarization, time delay between the pump and signal pulses, laser pulse energy, etc. We provide an explanation for the enhancement of third harmonic based on a quenching of interference effects present near filamentation threshold. Simulations based on a two-color propagation code reproduce well the experimental observations and confirm our interpretation. 相似文献
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We consider third harmonic generation in a periodic layered medium with alternate nonlinear media. We show enhanced third
harmonic generation when the fundamental frequency matches one of the mode frequencies of the distributed feedback structure.
The observed feature is explained in terms of large local field enhancement for the fundamental wave. 相似文献
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We demonstrate the third harmonic generation in a ZnO/Si layered structure to obtain high frequency SAW devices. This configuration eliminates the need of high lithography resolution and allows easy integration of such devices and electronics on the same wafer. A theoretical study was carried out for the determination of the phase velocity and the electromechanical coupling coefficient (K2) dispersion curves of the surface acoustic waves. These results are also in agreement with those measured on a SAW filter designed for the third harmonic generation and the operating frequency is up to 2468 MHz. 相似文献
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Virgilijus Vai?aitis Vygandas Jarutis Algirdas Stabinis 《Optics Communications》2011,284(12):3101-3104
Influence of transverse and longitudinal phase matching on the spectral and intensity properties of third harmonic generation induced by the Bessel pump beams has been investigated both theoretically and experimentally. Transverse phase matching, revealing itself as a ring pattern in the third harmonic intensity angular spectrum was demonstrated in both the normally and anomalously dispersive media. The conditions were found for the optimization of this conical third harmonic signal. 相似文献
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TANG Zhilie XING Da & LIU Songhao . Department of Physics South China Normal University Guangzhou China . School for Information Optoelectronic Science Engineering South China Normal University Guangzhou China Correspondence should be addressed to Tang Zhilie 《中国科学G辑(英文版)》2004,47(1):8-16
ItisreportedrecentlythatnonlinearopticalphenomenonofSHGandTHGhasbeenobservedinmanybiologicaltissues[16].SHGandTHGhavebeenusedtoperformthethree-dimensionalimaginginlivingtissuesandhaveattractedmuchattentionrecently.TherearemanyadvantagesofusingSHGandTHGtoperformthethree-dimensionalimaginginlivingtissues,suchasnoninvasiveandnophotobleaching,inadditiontotheimagingpropertiesofmulti-photonfluorescenceimaging[7—9].Firstly,unlikeinthesingle-andmulti-photonfluorescenceprocesses,onlyvirtualstat… 相似文献
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Effects of transverse profile of pump field on second harmonic generation in periodic nonlinear materials 下载免费PDF全文
We report on a theoreticalanalysis of the effects of a converging pump field of Gaussian transverse profile on second harmonic generation in a periodic nonlinear material with quasi-phase-matching. The outputs of the centre intensity and the intensity flux for second harmonic generation are derived by simulation, based on the parameters of quasi-phase-mismatch, the waist and focus positions of the input pump beam. The results show that when the transverse profile of the pump field is taken into account, the quasi-phase-match value and focus position of input beam for maximal second harmonic generation flollow new criteria. 相似文献
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A new scheme with non-collinear sum frequency generation (SFG) process of broadband third harmonic generation (THG) with two KDP crystals (one doubler and one mixer) using angular dispersion was proposed. The principle of broadband harmonic generation with non-collinear angular dispersion was presented. The comparison between the schemes of non-collinear and collinear SFG process was performed. The effects of the angular dispersion on the conversion efficiency, the pulse shape and the spectrum of the third harmonic field were discussed. The results show that, if proper angular dispersion is added to the fundamental and the second harmonic field outside the mixing KDP crystal, respectively, the broadband third harmonic conversion efficiency can be improved significantly. However, the difficulty of this scheme arises due to the requirement of two gratings with different angular dispersion outside the mixer. With the new scheme, it can be simpler that only one grating is needed to realize the broadband phase matching in the non-collinear SFG process. Although the fundamental and the second harmonic field inside the mixing crystal are non-collinear except the center wavelength, a blazing grating with proper angular dispersion for the fundamental field (twice as that for second harmonic field) can yield the well compensation for phase mismatching in the SFG process. Consequently, the conversion efficiency and the characteristics of the third harmonic field for the broadband third harmonic generation can be improved significantly. 相似文献
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Feasibility of nonresonant third harmonic generation in thallium is investigated. The third order susceptibility, for driving
frequencies in the visible region, is calculated and the phase matching with Ar as buffer gas is investigated. Other related
quantities like coherence length, minimum pulse lengths required to get phase matching and power input requirements to achieve
50% conversion are also calculated. 相似文献
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Third harmonic generation (THG) of high power laser is discussed in KDP crystals utilized in frequency conversion systems of large laser facilities. The far-field focal spot of the third harmonic wave is presented based on numerical simulation of the nonlinear coupled-wave equations, in which the walk-off and paraxial diffraction are taken into account and the electric field of the fundamental wave (1053 nm, 1ω) pulse is phase and amplitude modulated in spatial domain. Impact of the modulation depth and frequency on the focal spot energy, the side lobes location and conversion efficiency are analyzed in detail. The results show that the side lobes location is equivalently determined by the modulation frequency of both phase modulation and amplitude modulation, while the energy-concentration is decreased mostly because of the 1ω modulation depth. Relatively, the phase modulation plays a more important role than the amplitude modulation in decreasing main lobe energy for different reasons. The phase modulation makes the energy flowing from the main lobe to side lobes, while amplitude modulation not only makes the energy flowing but also decreases tripling efficiency significantly. 相似文献
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本文报道了采用基于熔石英薄片超连续的少周期飞秒光源驱动高次谐波产生的实验研究.实验中通过将重复频率1kHz的飞秒钛宝石激光放大器所输出的能量0.8mJ、脉宽30fs的脉冲聚焦到7片0.1mm厚的熔融石英片中,得到了覆盖带宽大于倍频程的展宽光谱.利用啁啾镜补偿色散后,经瞬态光栅频率分辨光学开关法测得脉宽为6.3fs,对应约2.3个光学周期.利用压缩后的激光脉冲聚焦作用于惰性气体,并通过调节尖劈插入量改变脉宽,分别测得了分立以及连续的高次谐波截止区信号,结果与6.3fs的脉冲宽度相符合. 相似文献
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S. Achilli M. Allione A. M. Malvezzi M. Patrini A. Stella P. Cheyssac R. Kofman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):223-226
In this work we use nonlinear optical properties of Ga
nanoparticles monolayers of different average sizes embedded in
dielectric matrices to investigate the liquid-solid phase
transitions in these materials. Ga nanoparticles, formed by
exploiting the partial wetting of liquid Ga over a
SiOx surface are irradiated with fs laser
pulses from a Ti:sapphire source. The resulting Second Harmonic
(SH) generated in the reflection and transmission directions is
measured along the phase transitions by cooling the sample from
320 K down to liquid nitrogen temperature. Hysteresis cycles are
observed in the nonlinear transmission, which exhibit a strong
amplification from the solid to liquid values as compared to the
linear optical results. A simple model for SH generation, based
on Mie scattering calculations which includes the effect of
surface plasmon resonance provides a fair key for the
interpretation of the observed effects. 相似文献
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随着纳米加工和制备技术的不断发展,金属纳米粒子的等离激元光学特性已得到了广泛的研究与应用。本文基于金属纳米颗粒等离激元共振特性,分析了金属纳米颗粒等离激元共振对介质谐波的增强机制,综述了该增强机制在近几年所取得的最新研究成果及其在生物成像领域的应用。金属纳米颗粒等离激元共振在增强介质非线性特性领域的发展趋势是从简单的金属纳米颗粒向复杂形状纳米颗粒和金属纳米颗粒组装体的发展,这些新型金属纳米颗粒在非线性光学、生物医学上的疾病诊断和治疗有良好的实际应用前景。 相似文献
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为提高强激光场与惰性气体靶作用产生的孤立阿秒激光脉冲的能量,给出了一种实现高次谐波过程中最佳谐波相位匹配的定量实验方法。研究了气体靶源与高斯型驱动激光场聚焦点相对空间位置对谐波相位匹配及谐波产率的影响,得出了其最佳相位匹配位置始终位于驱动激光场聚焦点后3~5 mm,而在聚焦点之前的位置区域,严重的高次谐波相位失配导致谐波产率非常低。同时,在最佳相位匹配条件下,高次谐波场与驱动场具有相类似的空间强度分布特性,该结果印证了目前通常采用的高次谐波场为高斯光束的假设。 相似文献
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E. C. Niculescu 《哲学杂志》2013,93(24):2089-2107
AbstractThe effects of an off-centre donor impurity on the non-linear optical absorption, second and third harmonic generation in a GaAs two-dimensional disc-shaped quantum ring under magnetic field are investigated within the compact density-matrix formalism and the effective mass approximation. The results reveal that: (i) the absorption spectra extend on larger energy intervals at the increment of the magnetic field; (ii) the possibility of generating second harmonic response from the system is demonstrated for an impurity placed on the repulsive part of the confining potential; (iii) both second harmonic and third harmonic coefficients are one order of magnitude larger for an impurity placed on the repulsive part of the potential and are blue-shifted by the increment of the magnetic field regardless the impurity position. 相似文献
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This work is used in the density matrix formalism and the effective mass approximation to study the third harmonic generation coefficient in a GaAs disc-shaped quantum dot with parabolic confinement potential. It is discussed the strong and weak confinement regime. The results show that the third harmonic generation coefficient is strongly dependent on the excitonic pair localization. The study is extended to consider effects such as hydrostatic pressure and temperature to show that it is possible to induce a blue-shift and/or red-shift on the resonant peaks of the third harmonic generation coefficient. 相似文献