作者希望感谢这项研究由国家自然科学基金（批准号：CMMI-0653578，CBET-0853890），提供金融支持。

1。光学系统的安装（图1） <ol><li>设立一个半波片和偏振片调整激光脉冲能量的激光输出。 </li><li>成立后，分裂的两个脉冲激光脉冲的偏光分光镜：泵脉冲和探测脉冲。 </li><li>使用4个反射镜和一本手册的翻译阶段兴建泵脉冲光延迟装置。 </li><li>使用另外四个反射镜引导泵脉冲到达靶面垂直。 </li><li>设置二次谐波发生器（SHG）从800纳米到400纳米的激光脉冲的波长变换。 </li><li>使用传输800 nm脉冲谐波分离和反映的400纳米脉冲。 </li><li>成立束减速和灶性镜片的的一双调整探头脉冲的大小和收敛。 </li><li>设立另一个光学延迟装置，如在步骤1.3中提到的探测脉冲。 </li><li>使用光圈环来调整该地区的脉冲探头，确保探头的脉冲传递水平和目标表面相交泵脉冲。 </li><li>成立两个物镜和几个过滤器产生的等离子体区域的形象，要加强电荷耦合装置（ICCD）相机收到。 </li><li>连接电脑，激光，ICCD相机和它的控制器使用BNC电缆或USB电缆。 </li><li>调整相机控制器的延迟时间，直到摄像头捕捉图像探头脉冲。因此，探测脉冲和相机是同步的。 </li></ol> 2。泵探针同步<ol><li>放置在路口泵脉冲和探测脉冲分光镜，并成立了两个光电二极管接收这两个脉冲。这两个光电二极管应该有一个相同的距离，离分光镜。 </li><li>使用这两个光电二极管接收信号，示波器和移动泵脉冲光束路径上的延迟阶段，直到亲文件泵脉冲和探测脉冲在示波器屏幕上互相重叠。由于示波器的时间分辨率达到20 ps的精度。 </li><li>卸下分光镜和步骤2.1中提到的两个光电二极管。 </li><li>调整泵脉冲光束路径上的延迟阶段可能只是见ICCD屏幕上观察到的空气击穿区域。当空气击穿形成一个统一的背景，而不是可检测的时间确定为延迟时间为零。 </li></ol> 3。采样和阶段作准备<ol><li>成立一个实验室插孔和两个手动线性阶段以三自由度移动样品。 </li><li>使用千分表和高精密垫片，实现了高平整度的阶段。高度差应在1微米每25.4毫米的距离。 </li><li>切输出表的铜方片厚度为0.8毫米（30毫米×30毫米），使用铣床机。 </li><li>擦亮的铜件窄边（30毫米×0.8毫米），直到表面粗糙度为0.5微米以下。 </li><li>修复铜件抛光窄面朝上顶端手册阶段。 </li><li>步骤3.1）中提到的目标，同时监测通过ICCD相机等任何倾斜，可以通过插入以下目标的高精度垫片调整它的位置移动了一本手册阶段。 </li><li>重复步骤3.6与其他手册阶段。 </li><li>第三精度高手册阶段而有所不同焦距镜头的位置，钻一个孔打在目标上。焦点位置相对应的焦距镜头，其中最小的孔钻的位置。 </li></ol> 4。消融和测量<ol><li>将焦距镜头离中心点约50微米的距离。 </li><li>移动探头上的脉冲光束路径的延迟阶段捕捉到10 ps的图像，每2个PS 0.3毫米的间隔，或3毫米的间隔捕获图像每20 PS至480 PS。 </li><li>重复多次的重复性和准确性的步骤4.2。 </li><li>将焦距镜头离中心点约50μm的距离，并重复步骤4.3。 </li></ol> 5。代表结果 如图测量的阴影图像。 2和图。 3，略高于低于目标表面的中心点，分别。纵向和径向膨胀位置图绘制。 4和图。 5。在第100 PS这两种情况下的纵向扩展有显着不同;然而，在下面的400 PS和径向扩展其纵向扩展是相似的。对于第一种情况下，早在100 ps的等离子体具有一维扩展结构，由多个层组成。对于第二种情况，早期的PL阿斯玛有一个两维的扩展结构，这并不能改变在100 ps的非常。 12的仿真模型，用于调查的早期血浆演化机制。被定义为时间零点时，激光脉冲的峰值达到目标表面。模拟早期的等离子演化过程以及与这两种情况下的测量结果一致， 如图所示。 6和图。 7，分别为。首次采用仿真模型的情况下形成的早期血浆内1个PS还预测图。 8。早期的血浆被发现有一个空气击穿区域和Cu等离子体区域。第一所造成的空气击穿多光子电离，雪崩电离。然而，对于第二种情况，重点是以下目标表面，并没有单独的空气击穿区域形成。相反，发生空气电离附近的铜解放军SMA前，并造成影响电离由于喷出的自由电子从铜的目标。 <img alt="图1" src="/files/ftp_upload/4033/4033fig1.jpg" /> 图1。泵探针阴影测量示意图。 <img alt="图2" src="/files/ftp_upload/4033/4033fig2.jpg" /> 图2。铜在连续的延迟时间与等离子体膨胀略高于表面的焦点。激光波长：800纳米，脉冲宽度为100 fs;功率密度：4.2×10 14瓦/厘米2;目标：铜。 <img alt="图3" src="/files/ftp_upload/4033/4033fig3.jpg" /> 图3。铜在连续的延迟时间与联络点，略低于表面的等离子体膨胀。激光波长：800纳米，脉冲宽度为100 fs;功率密度：4.2×10 14瓦/厘米2;目标：铜。 &lt;IMG ALT =“图4”的src =“/ files/ftp_upload/4033/4033fig4.jpg”/&gt; 图4。等离子纵向和径向膨胀略高于表面的焦点位置在连续的延迟时间。激光波长：800纳米，脉冲宽度为100 fs;功率密度：4.2×10 14瓦/厘米2;目标：铜。 <img alt="图5" src="/files/ftp_upload/4033/4033fig5.jpg" /> 图5。血浆纵向和径向膨胀职位，在连续的延迟时间与联络点，略低于表面。激光波长：800纳米，脉冲宽度为100 fs;功率密度：4.2×10 14瓦/厘米2;目标：铜。 图6。动画的测量和计算了70 ps的延迟时间内的血浆扩张略高于表面的焦点。激光波长：800纳米，脉冲宽度100 fs的功率密度：4.2×10 14 </suP&gt;瓦/平方厘米 ;目标：铜。 <a href="http://www.jove.com/files/ftp_upload/4033/4033movie6.avi" target="_blank">点击这里查看动画</a> 。 图7。动画的测量和计算了70 ps的延迟时间内血浆扩张略低于表面的焦点。激光波长：800纳米，脉冲宽度为100 fs;功率密度：4.2×10 14瓦/厘米2;目标：铜。 <a href="http://www.jove.com/files/ftp_upload/4033/4033movie7.avi" target="_blank">点击这里查看动画</a> 。 图8。动画的测量和计算的延迟时间在1个PS血浆扩大略高于表面的焦点。激光波长：800纳米，脉冲宽度为100 fs;功率密度：4.2×10 14瓦/厘米2;目标：铜<a href="http://www.jove.com/files/ftp_upload/4033/4033movie8.avi" target="_blank">点击这里查看动画&lt;</a>/ A&gt;。

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没有利益冲突的声明。

本文提出的测量和模拟方法可以​​更准确的检查早期等离子体动力学和更好地了解空气和铜的电离机制。高品质的等离子体结构捕获了1个PS和1微米的空间分辨率，时间分辨率。这种测量方法具有较高的重复性。关键步骤是对准光束非常好，准备与高平整度以及低粗糙度目标表面。 这种方法可以应用到其他目标的材料和各种激光参数。泵探针阴影方法唯一的限制是一个过低的电子数密度的变化。

<table border="1"><tbody><tr><td> 设备名称 </td><td> 公司 </td><td> 目录编号 </td></tr><tr><td>激光</td><td>光谱物理</td><td> SPTF-100F-1K-1P </td></tr><tr><td> ICCD相机</td><td>普林斯顿仪器</td><td> 7467-0028 </td></tr><tr><td>示波器</td><td> RIGOL </td><td> DS1302CA </td></tr><tr><td>光电二极管</td><td>纽波特</td><td> 818-BB30 </td></tr><tr><td>线性阶段</td><td>纽波特</td><td> 433 </td></tr><tr><td>百分表</td><td>三丰</td><td> ID-C112E </td></tr></tbody></table>

investigation of early plasma evolution induced by ultrashort laser pulses

由于目标的高强度激光照射和随后的目标物质电离产生早期血浆。在激光材料相互作用及其动力学1显着的作用，尤其是在空气环境1-11。 早期血浆进化已被抓获，通过泵式的探头shadowgraphy 1-3 1,4-7干涉。然而，研究的时间框架和应用的激光参数范围是有限的。例如，血浆前的位置和电子数密度与激光脉冲的峰值延迟时间为100皮秒（ps）内直接考试仍然很少，尤其是持续时间超短脉冲约100飞秒（fs）的，周围10〜14瓦/厘米2的功率密度低。在这些条件下产生的早期血浆最近被抓获，高时空分辨率12。详细的设置策略和本文将说明这种高精度测量程序。测量的基本原理是眼镜的泵探针shadowgraphy的：一个超短激光脉冲被分裂泵脉冲和探测脉冲，而它们之间的延迟时间可以调整，通过改变其光束路径长度。泵脉冲烧蚀的目标，并生成早期血浆和探测脉冲传播通过血浆地区和检测电子数密度非均匀性。此外，动画生成号的仿真模型的计算结果。12，说明等离子体的形成和演化具有非常高的分辨率（0.04〜1个PS）。 实验方法和模拟方法可应用于广泛的时限和激光参数。这些方法可以用来研究早期血浆产生的不仅是金属，但也从半导体和绝缘体。

Watch this Scientific Journal Video about Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses at JoVE.com

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

实验方法来研究早期的超短激光脉冲诱导的等离子体演化描述。使用这种方法，早期血浆中的高品质的图像，得到高时空分辨率。一种新型的集成原子模型被用来模拟和解释早期血浆机制。

超短激光脉冲诱导的等离子体演化早期的调查

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a ...

investigation-early-plasma-evolution-induced-ultrashort-laser

Research

JoVE Journal

Engineering

14.8K 次观看.  Purdue University. 实验方法来研究早期的超短激光脉冲诱导的等离子体演化描述。使用这种方法，早期血浆中的高品质的图像，得到高时空分辨率。一种新型的集成原子模型被用来模拟和解释早期血浆机制。

视频: Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

制备纳米设计的脉冲激光沉积透明导电氧化物

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

科研

工程学

Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle's Mapping and Quantification in Organ Tissue

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) performed on thin sections of rodent tissues: kidneys and tumor, allows the detection of inorganic elements such as (i) Na, Ca, Cu, Mg, P, and Fe, naturally present in the body and (ii) Si and Gd, detected after the injection of gadolinium-based nanoparticles. The animals were euthanized 1&#160;to 24 hr&#160;after intravenous injection of particles. A two-dimensional scan of the sample, performed using a motorized micrometric 3D-stage, allowed the infrared laser beam exploring the surface with a lateral resolution less than 100 &#956;m. Quantitative chemical images of Gd element inside the organ were obtained with sub-mM sensitivity. LIBS offers a simple and robust method to study the distribution of inorganic materials without any specific labeling. Moreover, the compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of the same biological tissue with different types of response:&#160;elemental, molecular, or cellular.

Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle&#039;s Mapping and Quantification in Organ Tissue

Laser-induced breakdown spectroscopy performed on thin organ and tumor tissue successfully detected natural elements and artificially injected gadolinium (Gd), issued from Gd-based nanoparticles. Images of chemical elements reached a resolution of 100 &#956;m and quantitative sub-mM sensitivity. The compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of a same biological tissue.

激光诱导击穿光谱：对于纳米粒子的映射和定量的器官组织的新方法

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) ...

Laser-induced Forward Transfer for Flip-chip Packaging of Single Dies

Flip-chip (FC) packaging is a key technology for realizing high performance, ultra-miniaturized and high-density circuits in the micro-electronics industry. In this technique the chip and/or the substrate is bumped and the two are bonded via these conductive bumps. Many bumping techniques have been developed and intensively investigated since the introduction of the FC technology in 19601 such as stencil printing, stud bumping, evaporation and electroless/electroplating2. Despite the progress that these methods have made they all suffer from one or more than one drawbacks that need to be addressed such as cost, complex processing steps, high processing temperatures, manufacturing time and most importantly the lack of flexibility. In this paper, we demonstrate a simple and cost-effective laser-based bump forming technique known as Laser-induced Forward Transfer (LIFT)3. Using the LIFT technique a wide range of bump materials can be printed in a single-step with great flexibility, high speed and accuracy at RT. In addition, LIFT enables the bumping and bonding down to chip-scale, which is critical for fabricating ultra-miniature circuitry.

We demonstrate the use of the Laser-induced Forward Transfer (LIFT) technique for flip-chip assembly of optoelectronic components. This approach provides a simple, cost-effective, low-temperature, fast and flexible solution for fine-pitch bumping and bonding on chip-scale for achieving high-density circuits for optoelectronic applications.

激光诱导转发转移单人死于倒装芯片封装

Flip-chip (FC) packaging is a key technology for realizing high performance, ultra-miniaturized and high-density circuits in the micro-electronics ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

硅表面润湿性的选择区域改性脉冲紫外激光照射在液体环境

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a stable and continuous operation of the plasma is possible and the plasma torch can be used for many different applications. On one hand, the hot (3,600 K gas temperature) plasma can be used for chemical processes and on the other hand the cold afterglow (temperatures down to almost RT) can be applied for surface processes. For example chemical syntheses are interesting volume processes. Here the microwave plasma torch can be used for the decomposition of waste gases which are harmful and contribute to the global warming but are needed as etching gases in growing industry sectors like the semiconductor branch. Another application is the dissociation of CO2. Surplus electrical energy from renewable energy sources can be used to dissociate CO2 to CO and O2. The CO can be further processed to gaseous or liquid higher hydrocarbons thereby providing chemical storage of the energy, synthetic fuels or platform chemicals for the chemical industry. Applications of the afterglow of the plasma torch are the treatment of surfaces to increase the adhesion of lacquer, glue or paint, and the sterilization or decontamination of different kind of surfaces. The movie will explain how to ignite the plasma solely by microwave power without any additional igniters, e.g., electric sparks. The microwave plasma torch is based on a combination of two resonators &#8212; a coaxial one which provides the ignition of the plasma and a cylindrical one which guarantees a continuous and stable operation of the plasma after ignition. The plasma can be operated in a long microwave transparent tube for volume processes or shaped by orifices for surface treatment purposes.

This movie shows how an atmospheric plasma torch can be ignited by microwaves with no additional igniters and provides a stable and continuous plasma operation suitable for plenty of applications.

如何点燃常压微波等离子体炬没有任何额外的点火器

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

锁模自动化的非线性偏振旋转光纤激光器通过输出偏振测量

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Laser-induced Forward Transfer of Ag Nanopaste

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip.

We demonstrate the use of the Laser-induced forward transfer technique (LIFT) for the printing of high-viscosity Ag paste. This technique offers a simple, low temperature, robust process for non-lithographically printing microscale 2D and 3D structures.

银纳米糊膏的激光诱导正向传输

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of ...

An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O2, N2, air, H2O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of &#39;high&#39; voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry.

An experimental setup was created for the helium-operated kHz frequency plasma jet. The setup includes a cage for the plasma power supply and jet and an in-house built reactor to monitor plasma-induced reactive species without the interference of the ambient atmosphere.

大气压等离子体设置调查活性物种形成

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. ...

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using femtosecond laser-induced ablation. We show that thousands of periodic nano-craters are fabricated on an optical nanofiber by irradiating with just a single femtosecond laser pulse. For a typical sample, periodic nano-craters with a period of 350 nm and with diameter gradually varying from 50 - 250 nm over a length of 1 mm are fabricated on a nanofiber with diameter around 450 - 550 nm. A key aspect of such a nanofabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. Moreover, the single-shot fabrication makes it immune to mechanical instabilities and other fabrication imperfections. Such periodic nano-craters on nanofiber, act as a 1-D PhC and enable strong and broadband reflection while maintaining the high transmission out of the stopband. We also present a method to control the profile of the nano-crater array to fabricate apodized and defect-induced PhC cavities on the nanofiber. The strong confinement of the field, both transverse and longitudinal, in the nanofiber-based PhC cavities and the efficient integration to the fiber networks, may open new possibilities for nanophotonic applications and quantum information science.

We present a protocol for fabricating 1-D photonic crystal cavities on subwavelength diameter silica fibers (optical nanofibers) using femtosecond laser-induced ablation.

1-D光子晶体空穴对纳米纤维使用飞秒激光诱导消融制造

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

使用激光投射光热法构造加热的地下缺陷定位

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...