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1.
孙玉萍  刘纪彩  王传奎 《物理学报》2009,58(6):3934-3942
以具有强双光子吸收特性的4,4′-二甲氨基二苯乙烯分子体系为研究对象,通过采用时域有限差分法和预估矫正法数值求解Maxwell-Bloch方程,模拟了飞秒脉冲在该分子介质中的传播过程,研究了含时电离对双光子吸收过程和光限幅行为的影响.研究结果表明,光电离使介质与光场的非线性相互作用减弱,同时自发辐射降低, 随着入射电场的增强,光电离对主脉冲演化有明显的影响.光电离使介质的光限幅失效行为减弱.随着光电离截面增加,光限幅的动力学窗口变宽,表明了光电离有利于增强介质的光限幅效应.在不同的传播距离处,脉冲传播呈现 关键词: 含时电离 双光子吸收 光限幅效应 超短脉冲激光  相似文献   

2.
王先华  陈烽  杨青  陈涛  梁松 《应用光学》2007,28(2):191-194
鉴于飞秒激光脉冲持续时间极短且峰值功率极高,将其紧聚焦到透明介质体内部时,易引发双光子效应、碰撞电离、雪崩击穿等一系列非线性过程,在焦点处产生微爆,从而形成微腔结构。提出采用25fs的激光脉冲在透明介质内部诱导形成微腔结构。分析了微腔的能量阈值。结合三维精密位移台,制备了三维微腔点阵。探讨了超短激光脉冲在透明介质内部形成微腔结构的方法与基本实验参数。试验发现:采用更短脉宽的飞秒脉冲时可以降低微腔形成的能量阈值;通过调整飞秒激光功率、脉冲作用次数和光束聚焦情况等因素,可以有效改变微腔的纵深比;在数值孔径较低时因无法实现紧聚焦,故不能形成微腔。  相似文献   

3.
相位对比读出三维光数据存储的实验研究   总被引:4,自引:4,他引:0  
使用波长800 nm、脉冲宽度150f s的近红外激光脉冲紧聚焦到PMMA(聚甲基丙烯酸甲酯)和熔融石英中实现了三维逐位式光数据存储,分别记录下了5、10、 15和20层数据位点.利用相位对比光学显微原理对各层数据并行读出,实验分析了各层数据位点的读出对比度的变化.结果表明:各层数据位点的折射率对比度由内至外依次增加,记录层数越多,其内部层的对比度下降越明显.由于飞秒激光脉冲与透明介质相互作用中,熔融石英内部产生的残余应力比PMMA内大,因此数据位点参数相同的情况下,利用PMMA材料记录的层数更多.  相似文献   

4.
实验研究了飞秒激光脉冲诱导熔融石英的非线性吸收特性,利用激光诱导自由电子等离子体浓度取决于多光子吸收系数和入射光强的关系;数值模拟了激光诱导折射率变化区域的大小,结合非线性吸收机理和飞秒激光脉冲与介质的相互作用,解释了飞秒激光脉冲超精细加工不受衍射极限的约束,可实现纳米级加工的机理结果表明,电介质的电离能越大,飞秒脉冲诱导的折射率变化区域就越小,但要求的激光脉冲能量也越大;为飞秒激光脉冲超精细加工的材料和激光参量选择提供了理论依据.  相似文献   

5.
飞秒激光在三维微细体系中的应用   总被引:3,自引:0,他引:3  
李承德  王丹翎  罗乐  杨宏  龚旗煌 《物理》2000,29(12):719-723
飞秒激光的超快特性使其能以极低的脉冲能量获得超强光场,并且激光加照区淀积的能量能以通过热扩散途径逸出辐照区域,其与透明物质相互作用是通过双光子或多光子吸收过程实现,故作用区限域于焦点核心很小体积内,因而在三维微制备及生物医学领域有着独到优势。文章介绍了飞秒激光应用于微爆炸、高密度三维光学数据存储、直写光波导及三维光子晶体制备、生物医学工程等方面的最新进展。飞秒激光三维微制备技术在微电子、计算机、光通信、生物医学等高技术领域有着广阔的应用前景。  相似文献   

6.
多光子纠缠态是量子通讯网络中的重要资源,光与二阶非线性介质相互作用的自发参变下转换过程是目前制备多光子态较成熟的方案之一.尽管脉冲光可以提高非线性转换效率并简化通信协议,但是进一步增强光与介质间的相互作用对提高多光子的产生效率依然必要.设计了飞秒脉冲激光谐振腔系统,在不改变脉冲重复频率和频率梳结构的情况下,提高了下转换...  相似文献   

7.
陈国夫 《物理》2005,34(10):725-730
随着飞秒(1fs=1×10-15s)激光技术的不断成熟,飞秒激光器不但在实验室能产生小于10fs的光脉冲,啁啾放大后的飞秒光脉冲的聚焦峰值功率密度可达到1021W/cm2以上,而且飞秒激光系统已实现全固体、小型化结构,其稳定性和可靠性大大提高,因此在科学技术研究中的应用越来越广.文章重点介绍飞秒激光的主要特性和它与透明介质[如熔融石英、光学玻璃、对激光透明的高分子聚合物(PMMA)等]的相互作用过程,分析它们之间的非线性相互作用过程引起的材料特性或结构变化的物理机制和可能的应用,尤其在高密度大容量三维存储和微光子器件制造等方面的应用可能性.  相似文献   

8.
啁啾飞秒激光脉冲形成的光纤光栅的Bragg反射特性   总被引:1,自引:0,他引:1       下载免费PDF全文
在800nm飞秒脉冲激光照射下光敏玻璃As2S3光纤具有双光子吸收 现象,当一束超短激光脉冲与另一束啁啾超短激光脉冲在As2S3光纤相遇时,干涉图案将 永久地记录一个空间啁啾光栅.研究了该光栅结构与入射超短脉冲激光脉冲参数的关系,数值计算表明该光栅具有较大的Bragg反射带宽. 关键词: 啁啾光纤光栅 飞秒激光脉冲 双光子吸收效应  相似文献   

9.
采用脉冲数字全息技术实现对飞秒级超快动态过程的数字显微全息记录.其中,全息记录系统将单脉冲分割成具有飞秒至皮秒量级时间延迟的角度相同的物光子脉冲序列和具有同样时间延迟的角度不同的参考光子脉冲序列,并以空间角分复用的方式在普通CCD的一帧图像上记录下包含多张子全息图的复合全息图,然后通过数字傅里叶变换和数字滤波的方法,分别再现出每张子全息图所记录的图像.通过对飞秒激光激发空气电离过程的全息记录,获得了具有飞秒时间分辨的等离子体形成和传播过程的动态图像. 关键词: 超短脉冲激光 飞秒全息 脉冲数字全息 空间角分复用  相似文献   

10.
邱建荣 《物理》2003,32(9):590-595
飞秒激光是近年来获得迅速发展的一种超快激光.超短脉冲和超高电场强度是它的两个特征.飞秒激光已广泛用于物理化学反应的动力学过程分析和热效应可忽略的超精细加工.利用飞秒激光与材料的非线性相互作用,还可以实现透明材料内部有空间选择性的三维调控光功能微结构.文章重点介绍了在可擦重写三维超高密度光存储、立体彩色内雕、可集成超快光开关等方面的应用和国内外相关领域的最新进展,并展望了应用前景。  相似文献   

11.
Optically produced arrays of planar nanostructures inside fused silica   总被引:1,自引:0,他引:1  
Linearly polarized femtosecond light pulses, focused inside fused silica to an intensity that leads to multiphoton ionization, produce arrayed planes of modified material having their normal parallel to the laser polarization. The planes are < or = 10 nm thick and are spaced at approximately lambda/2 in the medium for free space wavelengths of both 800 and 400 nm. By slowly scanning the sample under a fixed laser focus, order is maintained over macroscopic distances for all angles between the polarization and scan direction. With the laser polarization parallel to the scan direction we produce long-range Bragg-like gratings. We discuss how local field enhancement influences dielectric ionization, describe how this leads to nanoplane growth, why the planes are arrayed, and how long-range order is maintained.  相似文献   

12.
A two-dimensional axisymmetric model of the propagation of intense femtosecond laser pulses through dispersion-free transparent media is described. The effects of diffraction, nonlinear Kerr effect (instantaneous and retarded) and multiphoton ionisation are included. Numerical results concerning air and other gases are discussed. In particular, time self-compression of femtosecond pulses is predicted. Stable self-guided pulses are simulated, in agreement with recent experimental observations. Received: 19 June 1998 / Received in final form: 14 January 1999  相似文献   

13.
The photo-bleaching of single living cells excited by femtosecond laser irradiation was observed in situ to study the nonlinear interaction between ultrafast laser pulses and living human breast MDA-MB-231 cells. We conducted a systematic study of the energy dependence of plasma-mediated photo-disruption of fluorescently labeled subcellular structures in the nucleus of living cells using near-infrared (NIR) femtosecond laser pulses through a numerical aperture objective lens (0.75 NA). The behavior of photo-bleached living cells with fluorescently labeled nuclei was observed for 18 h after femtosecond laser irradiation under a fluorescence microscope. The photo-bleaching of single living cells without cell disruption occurred at between 470 and 630 nJ. To study the photo-disruption of subcellular organelles in single living cells using the nonlinear absorption excited by a NIR femtosecond laser pulse, the process of photo-bleaching without photo-disruption provides key information for clarifying the nonlinear interaction between NIR ultrashort, high-intensity laser light and transparent fluorescently labeled living cells.  相似文献   

14.
The exclusive ability of laser radiation to be focused inside transparent materials makes lasers a unique tool to process inner parts of them unreachable with other techniques. Hence, laser direct-write can be used to create 3D structures inside bulk materials. Infrared femtosecond lasers are especially indicated for this purpose because a multiphoton process is usually required for absorption and high resolution can be attained. This work studies the modifications produced by 450 fs laser pulses at 1027 nm wavelength focused inside a photostructurable glass-ceramic (Foturan®) at different depths. Irradiated samples were submitted to standard thermal treatment and subsequent soaking in HF solution to form the buried microchannels and thus unveil the modified material. The voxel dimensions of modified material depend on the laser pulse energy and the depth at which the laser is focused. Spherical aberration and self-focusing phenomena are required to explain the observed results.  相似文献   

15.
A theory of nonlinear absorption of femtosecond light pulses by bulk crystals and nanostructures of differing dimensionality is developed. The pulse width is assumed to be small compared to the relaxation times of the electron and hole momenta. Expressions for the absorbed energy under conditions of multiphoton resonance are derived for transitions between discrete or band-related electron states and between sub-band states of size quantization in quantum wells and quantum wires. The dependence of the absorbed energy on the multiphoton resonance detuning and pulse width is analyzed.  相似文献   

16.
Whispering-gallery-mode(WGM) microcavities with high-quality factors and small volumes have attracted intense interests in the past decades because of their potential applications in various research fields such as quantum information, sensing, and optoelectronics. This leads to rapid advance in a variety of processing technologies that can create high-quality WGM micro-cavities. Due to the unique characteristics of femtosecond laser pulses with high peak intensity and ultrashort pulse duration, femtosecond laser shows the ability to carry out ultrahigh precision micromachining of a variety of transparent materials through nonlinear multiphoton absorption and tunneling ionization. This review paper describes the basic principle of femtosecond laser direct writing, and presents an overview of recent progress concerning femtosecond laser three-dimensional(3D) fabrications of optical WGM microcavities, which include the advances in the fabrications of passive and active WGMs microcavities in a variety of materials such as polymer, glass and crystals, as well as in processing the integrated WGM-microcavity device. Lastly, a summary of this dynamic field with a future perspective is given.  相似文献   

17.
通过改变辐照激光脉冲数、激光的平均功率、显微镜物镜倍数/数值孔径等研究微皇冠结构形成与加工条件的关系,并借鉴激光熔池形成和液滴溅射的模型对其进行理论分析。当激光脉冲数达到一定数量后,烧蚀区域会出现微皇冠结构。烧蚀区域尺寸的改变是由于形成的液体区域中热毛细作用和化学毛细作用共同所致;微皇冠结构溅射个数的改变是由于形成的气体因多光子吸收体积迅速膨胀所致。  相似文献   

18.
We utilize the interaction of tightly focused ultrashort pulses with transparent media to imprint their local polarization in the focal region. In particular, we demonstrate that this technique allows for a subwavelength resolution diagnostic of complex polarization states including the presence of the longitudinal component of the electric field. Moreover, we demonstrate the first ever material ablation with the longitudinal electric field of femtosecond pulses.  相似文献   

19.
In recent years, femtochemistry and femtobiology have been quickly progressing. The specific characteristics of femtosecond pulses have extended the possibilities of traditional experiments and allowed obtaining new previously inacceptable information. New lines of research have emerged. This publication overviews studies performed at the Semenov Institute of Chemical Physics of the Russian Academy of Sciences. These studies cover three new directions: the mechanisms of intramolecular physicochemical processes occurring on the femto-picosecond timescale, coherent photochemistry based on the action of femtosecond pulses, and physicochemical processes initiated by multiphoton absorption of femtosecond radiation. The scope of these directions is illustrated by the results of studies of actual chemical and biological systems.  相似文献   

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