This work was funded by the Science and Technology Facilities Council (STFC).

序言：在本协议部分中，我们假设，一个纯粹的，噪音低，功率稳定的基模高斯光束，例如含图3中所示的标准设置，通过商业的Nd：YAG激光器产生连续波在1064纳米的波长的光;法拉第隔离器（FI），以避免对激光源的背面反射的光的一个电光调制器（EOM）的红外光的光的相位调制。由此产生的光束被注入到一个三角形的光学谐振腔，其中通过有效的控制回路27的激光频率的光功率稳定，而谐振腔提供不必要的波束形状的空间滤波。 上面描述的设置， 如图3所示，是一个传统的实验安排，科学装置中使用的精度要求低噪声激光稳定测量1-8。协议部分说明这个基本模式高斯光束可以有效地转换成高阶拉盖尔 - 高斯光束相媲美的表演，如果不相同，在纯度，噪声和稳定。这是通过所示的装置在图4中 ，其设计，建设，和操作在下面的章节描述的装置。在这项工作中提出了在这个例子中，所生成的模式将是一个所有33。然而，值得强调的是​​，该技术具有普遍的有效性和描述的协议，适用于任何所需的高阶LG模式。 1。光学模式转换为基本模式激光束的优化转换高阶LG梁的设计和原型一个基本模式束转换成高阶LG光束的相位调制档案中的要求是复制的相位CROβ-边的所需的LG模式，该模式将被印上的波阵面的入射光束26通过成比例的相移。两种类型的模式转换器以这种方式工作：空间光调制器（SLM） - 计算机控制的液晶显示器，其可以控制到压印相的像素上的入射光转变 - 衍射相位板 - 蚀刻玻璃基板所需在传输中产生的相移由故意不同厚度的玻璃元件。 SLM的是灵活的，但缺乏稳定性和效率，而相位板是稳定的，有效的，但缺乏灵活性。因此，我们建议使用最初的研究和原型设计和使用的相位板的长期操作的SLM。 最佳的转换依赖于精确的选择参数（腰围的大小和位置）的形状的光束。因此，注入到模式转换器之前，最初的基本模式时，必须将其特征在于，和它的参数重新塑造，以提供最佳的转换的匹配 - 该操作被称为“模式匹配的”。 <ol><li>拿起束从图3中描述的基本模式设置。 </li><li>使用光束分析仪配备了实时图像分析软件，可以衡量光束半径沿光路。一旦已获得足够一套半径（一般至少10个数据点都需要一个良好的质量结果），适合测量半径和提取束腰的规模和它的位置。 </li><li>建立所需的光束半径转换点。使用大束数毫米大小的顺序才能使用相位转换区域的充分程度。 </li><li>选择一组沿光路的透镜和它们的位置，将重新塑造成所需的入射光束参数（腰围的大小和位置）。对于对齐的目的，可以很方便地放置的模式转换器吨的入射光束的腰身。 </li><li>重复步骤1.2和1.4，通过连续的透镜位置调整，直到已获得所期望的光束模式转换参数。 </li><li> SLM模式转换沿入射光束路径，并注入到SLM束。反射型SLM，我们建议使用一个小的入射角度，5度或以下的订单。在生成的光束入射角大，会造成散光，打破了LG模式圆柱对称。 </li><li>应用相位分布到SLM的液晶显示装置 - ，相位将其转换为所需的高阶LG电子束的横截面。 33的LG模式，这是目前的研究在未来的毛重检测器16的应用程序，在图5中所示的例子中的相位调制模式。 </li><li>选择适当的相位图案的大小（对应的光束的相位图案的大小）的大小的基础上的注入TED束表1到9的顺序，使用数值模拟28导出最佳的光束大小比为LG模式的列表。或者，找到最佳的光束是通过改变施加到空间光调制器的相位图案的大小和分析所得到的光束的图像的图像尺寸比实验。 </li><li>观察反射光束从SLM使用的CCD照相机，在距离中的一个或多个瑞利范围相差从SLM。仔细对准，以优化在CCD上的光束的对称图像的SLM。 </li></ol>一些注入光的相位调制装置的交互期间，仍然未调制的相位调制电平由于量化。此未转化的光转换后的光束沿同一轴线上，损坏所需的相位调制效应。为了规避这个问题，可以对LG模式转换相位图像覆盖闪耀光栅轮廓。调制后的升搭载LG模式相位轮廓的洞察力将闪耀光栅偏转，而未灯光，不与基材互动的，将继续不受干扰。这将导致在两种类型之间的光束的空间分离。 <ol start="10"><li>熊熊结构重叠先前SLM产生的相位分布。 LG模与方位指数升&gt; 0的相位图案将有一个叉形光栅的特点，如在图6的例子中看到。 </li><li>优化燃烧的角度，使得入一阶的衍射角的光束的发散角大于。继续进行，直到较高的衍射级之间的一个合理的分离结果（使用作为外圈本身的直径一样大的连续梁的外圈之间的分离）。 </li><li>一旦实现最佳的转换模式，进行相板的制造。这些是商业上阿瓦伊标签和制造，以满足广泛的定制要求。使用与SLM在优化过程中所获得的结果，确定最佳的相位变换的图案被蚀刻到的相位板。可选步骤：应用中的至少一个的相位板的表面上的防反射涂层，以尽量减少散射的光反射回的光功率向所述激光源和分散。 </li></ol> 2。相板，模式转换和纯度增强操作<ol><li>更换空间光调制器的相位板。至于在SLM，它是方便的，以将其定位在注入的基本模式要转换的光束的腰身。 </li><li>小心地将相位板等的初始光束的相位板是垂直于梁，相对于光束的中心的相结构。 </li><li>传播的光束透过的相位板，直到较高的差异分离raction订单发生。梁与梁卡可以很容易地可视。 </li><li>当达到一个足够的“好”的分离（在步骤1.12中所述），遮掩较高的衍射级次光束的孔为中心的主衍射阶。 </li></ol>所讨论的相位板设计，不能调节幅度以及相位意味着他们将不能转换成所需的模式所有传入的根本束。其结果是一个组合梁的显性其他高阶模式轻微的强度，如在图7中示出的背景下进行所需的LG光束。为了在空间上过滤掉不想要的LG模式和增强模式的纯度，可以将转换后的光束的光学谐振腔的注入。这样的空腔，也可作为一个“模式选择”只允许特定的光学模式的传输，相对于光的波长的谐振腔长度根据。 <ol start="5"><li>设计莫清洁腔。如果在其实施简单，使用由两个反光镜的线性腔结构， 如图4所示，在这种反射镜是平的（通常是输入镜）和其他的反射镜（输出）是凹的。这提供了实施的光稳定性和简单。甲行之有效的具体设计是一个的输出反射镜的曲率半径为1米，而反射镜的反射表面之间的距离是21厘米29。在这种情况下，最佳的输入光束半径大约是365微米在腰部，位于平面镜的反射表面。 </li><li>选择腔镜的反射率来确定的腔技巧。使用低为了几百技巧，有良好的抑制不必要的模式订单，而不会引入大的扭曲，由于耦合退化模式（见第4步）。最好是使用具有相同反射率的反射镜，以最大限度地提高模腔通过。 </li><li>使用RIGID间隔为两腔的支持反映机械振动增强免疫力。胶的反射镜在隔板上，并插入一个压电环元件之间的两个反射镜的一个，与间隔件的纵向长度的控制和稳定的目的，以允许谐振腔长度的微观调整。 </li><li>模式匹配的光束所产生的相位板模式清洁器腔体本征模式。的LG光束的束仿形可以不被执行使用相同的工具用于根本模式束，因此，记录的强度分布的光束与一个放置在不同的位置沿光束路径的CCD相机和分析采用量身定制合身的记录，图像脚本，它可以识别主导的LG模式和光束半径估计在给定的位置30。该光束的强度分布拟合程序的一个例子示于图8。 </li><li>一旦有足够的光束直径已成为连接测量（通常，至少10个数据点所需要的良好的质量的结果），适合测得的半径和外推的束腰直径和它的位置。一个很好的光束轮廓看起来像一个如图9所示。在1.2和1.4，选择透镜，并重复该过程，直到最优波束的大小和位置被发现，2.7，2.8和2.9中描述。一旦实现模式匹配，注入所产生的光束进入模式吸尘器腔，确保输入（平坦）的反射面的反射镜是否正确放置在腰部注入光束。 </li><li>到空腔优化注入的光束的对准，同时，通过移动反射镜与压电扫描腔长，监视发送波束。 </li><li>使用由模式清洁器腔作为调查对LG光束所产生的相位板的模式内容的谐振腔长度（也称为空腔扫描）的函数的透射光的测量，前夕ntually评估的相位板本身的转换效率。 </li><li>通过检查的CCD图像识别有关的寄生模式。评估这种模式下的功率通过在光电二极管的信号其振幅和计算准确的整体光束的模式的内容。的测量结果和确切形式的内容可以进行复制，数值模拟21。的分析结果在图10中给出一个很好的例子，模式含量结果示于表2。 </li></ol>一旦成束的最佳取向模式清洁器腔被实现，分析已注入的光束模式的内容，可以最终实现方式清洁和增强的复合LG束纯度。一斤德雷弗霍尔锁定方案27可用于稳定腔长到所需的谐振模式。光传输模式吸尘器CAVITY可以读取由一个光电二极管，它可以提供错误的信号所​​必需的控制回路，控制腔长。 <ol start="13"><li>腔长锁定到发送的诊断所产生的光束，并限定其纯度与CCD摄像机的空腔产生的光束的档案的主共振和记录图像。 </li></ol> 3。生成的LG光束诊断和表征在这个实验中，两个主要的属性定义一个&#39;好&#39;光束质量的高精度干涉测量的成功实施：束功率和光束的纯度。使用上实现的基本模式的光束中，如上所述的相同的控制技术，可以保存其他相关的属性如频率或功率稳定。 <ol><li> LG电子束功率测量，通过激光功率计。注意梁剪切：LG光束具有较大EXTEN锡永相比，传统的高斯光束，它可能会超过大多数商业工具的敏感面积的尺寸。最高权力明显。 </li><li>通过比较与理论光束​​剖面评估生成的LG电子束的纯度。要做到这一点，通过CCD相机探查和拍摄照片的光束强度估计它的光束半径，推导出理论束振幅剖面比较测量。通过评估的纯度平方内积<img alt="公式1" fo:src="/files/ftp_upload/50564/50564eq1highres.jpg" src="/files/ftp_upload/50564/50564eq1.jpg" />理论和测量振幅分布。高纯度的建议。 </li></ol>两个重要的品质因数是有用的的整个模式转换过程中的质量评价：相板的转换效率和整体设置。 <ol start="3"><li>为了评估CONVERS离子相板效率，遵循腔扫描程序步骤2.11和2.12。 </li><li>评估的生成所需的LG光束的功率与注入基模高斯光束的功率之间的比率设置为整体的转换效率。高转换效率显然是可取的。 </li></ol> 4。注入大干涉模拟研究这个协议的应用之一是调查他们的引力波探测器使用LG光束。这些长基线高精度干涉。基线需要比较大的反射镜和光束大小。然而，这提高了不完善的光学元件的影响，特别是当使用高次模。本节介绍了一种基于模拟的方法进行调查的行为高阶LG模式在现实探测器。 <ol><li>选择光场建模仿真工具，在interferomet的呃为了测试高阶LG模式。仿真软件应该能够在设置不完善的影响（错位，模式不匹配，镜子数字错误等 ）建模的模式内容的光束。一个例子是仿真工具FINESSE 28。 </li><li>建立一个模型，一个真正的探测器使用选定的模拟工具。在高级LIGO的情况下，这是一个双循环迈克耳孙干涉仪臂腔的Fabry-Perot。这些初始模拟的目的是验证了模型的可靠性，假设完美的光学系统。 </li><li>测试模型与完善的基本模式横梁。为了验证该模型的可靠性，这应该允许再生的列表，在实际的检测器进行的实验程序，如：对臂腔，腔的扫描循环中的电源，如预期的数字误差信号，并检查，并角度和长度的干涉仪，其子系统的控制S通过传感和控制方案。进一步的模拟应包括干涉仪引力波信号的响应。一旦模拟按预期执行，该模型可以适于高阶LG模。 </li><li>测试模型与完美的LG33梁：适应干涉仪的设计，使用LG模式。这就需要减少上的空腔，其中可以实现通过改变的反射镜的曲率半径的反射镜的光束的大小。一旦模型已被改编为LG模式，应重复进行的测试4.3的新的输入束。如果在完美的光学系统的情况下，结果应该是非常相似，使用HG 00（见实例19）。 </li></ol>使用更高阶的光束引入了简并性的光学腔，因为有几个不同的光束形状，争取主导地位。高斯模式的光学谐振腔的谐振该命令适用于所有模式。一个HG00 0阶模式是唯一的模式，因此所有其他模式抑制。例如，LG 33模式10模式9阶的一个，所有这些都将在干涉仪得到加强。镜面扭曲，总是存在于真实的干涉夫妇到其他的事件模式。如果这些新的模式是相同的顺序，作为入射光束在臂腔增强，导致高度扭曲的循环光束。这最终会恶化仪器的灵敏度。 <ol start="5"><li>设置一个现实的干涉模型：将腔反射镜的表面数字的真实数据。此数据的属性几何高度或反射率的反射镜的表面，如一个“地图”的形式，在图11中的高级LIGO镜子看到一个例子。包括这些影响后，高阶模的性能，应进行调查，特别是在在检测器的输出和误差信号中的多个过零点的可能性的对比度缺陷。在这些领域中，高阶模式预计将表现逊于HG 00。 </li><li>模拟子系统：为了更好地了解模型中存在的退化效果，模拟子系统简，例如高级LI​​GO的法布里 - 珀罗臂腔。这些子系统模拟产生腔内扫描和错误信号，以识别任何的频率分裂和流通领域的检测，可以分析其模式内容。 </li><li>镜面要求：获得更严格的要求的情况下镜面的平整度4.6步的结果显示这将使执行高阶LG光束不可能在其他模式下的频率分裂或电源不可接受的程度。对于这一点，分析耦合等造成的直接跨阶其中可以实现数字或使用的解析近似19的表面。使用这种方法来识别任何特定的镜子的形状，是造成大量相同的顺序输入光束和模式之间的耦合。通过比较这些结果与模拟，估算为这些形状的镜像要求，对于一个特定的循环束纯度。最后模拟满量程的干涉仪模型修改为新规格的镜像地图，示出了改进对比度的缺陷和频率分裂。 </li></ol>

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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=the+LIGO+Collaboration.+Advanced+LIGO:+the+next+generation+of+gravitational+wave+detectors.">the LIGO Collaboration. Advanced LIGO: the next generation of gravitational wave detectors.</a> Classical and Quantum Gravity. 27, 084006 (2010).</li><li>Accadia, T., Acernese, F., Antonucci, F., Astone, P., Ballardin, G., Barone, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Status+of+the+VIRGO+project.">Status of the VIRGO project.</a> Classical and Quantum Gravity. 28, 114002 (2011).</li><li>Sathyaprakash, B., Abernathy, M., Acernese, F., Ajith, P., Allen, B., Amaro-Seoane, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scientific+objectives+of+Einstein+Telescope.">Scientific objectives of Einstein Telescope.</a> Classical and Quantum Gravity. 29 (12), 124013 (2012).</li><li>Bondarescu, M., Thorne, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+family+of+light+beams+and+mirror+shapes+for+future+LIGO+interferometers.">New family of light beams and mirror shapes for future LIGO interferometers.</a> Physical Review D. 74, 082003 (2006).</li><li>Bondarescu, M., Kogan, O., Chen, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimal+light+beams+and+mirror+shapes+for+future+LIGO+interferometers.">Optimal light beams and mirror shapes for future LIGO interferometers.</a> Physical Review D. 78, 082002 (2008).</li><li>Tournefier Mours, E., Vinet, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+noise+reduction+in+interferometric+gravitational+wave+antennas:+using+high+order+TEM+modes.">Thermal noise reduction in interferometric gravitational wave antennas: using high order TEM modes.</a> Classical and Quantum Gravity. 23, 5777 (2006).</li><li>Chelkowski, S., Hild, S., Freise, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prospects+of+higher-order+Laguerre-Gauss+modes+in+future+gravitational+wave+detectors.">Prospects of higher-order Laguerre-Gauss modes in future gravitational wave detectors.</a> Physical Review D. 79, 122002 (2009).</li><li>Vinet, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reducing+thermal+effects+in+mirrors+of+advanced+gravitational+wave+interferometric+detectors.">Reducing thermal effects in mirrors of advanced gravitational wave interferometric detectors.</a> Classical and Quantum Gravity. 24, 3897 (2007).</li><li>Fulda, P., Kokeyama, K., Chelkowski, S., Freise, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+demonstration+of+higher-order+Laguerre-Gauss+mode+interferometry.">Experimental demonstration of higher-order Laguerre-Gauss mode interferometry.</a> Physical Review D. 82, 012002 (2010).</li><li>Bond, C., Fulda, P., Carbone, L., Kokeyama, K., Freise, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Higher+order+Laguerre-Gauss+mode+degeneracy+in+realistic,+high+finesse+cavities.">Higher order Laguerre-Gauss mode degeneracy in realistic, high finesse cavities.</a> Physical Review D. 84, 102002 (2011).</li><li>Sorazu, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+test+of+higher-order+Laguerre-Gauss+modes+in+the+10+m+Glasgow+prototype+interferometer.">Experimental test of higher-order Laguerre-Gauss modes in the 10 m Glasgow prototype interferometer.</a> Class. Quantum Grav. 30, 035004 (2013).</li><li>Carbone, L., Bogan, C., Fulda, P., Freise, A., Willke, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+High-Purity+Higher-Order+Laguerre-Gauss+Beams+at+High+Laser+Power.">Generation of High-Purity Higher-Order Laguerre-Gauss Beams at High Laser Power.</a> Physical Review Letters. 110, 251101 (2013).</li><li>Fulda, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phaseplate+design+for+Laguerre-Gauss+mode+conversion.">Phaseplate design for Laguerre-Gauss mode conversion.</a> , (2013).</li><li>Willke, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stabilized+lasers+for+advanced+gravitational+wave+detectors.">Stabilized lasers for advanced gravitational wave detectors.</a> Laser &amp; Photonics Rev. , 1-15 (2010).</li><li>Granata, M., Buy, C., Ward, R., Barsuglia, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Higher-Order+Laguerre-Gauss+Mode+Generation+and+Interferometry+for+Gravitational+Wave+Detectors.">Higher-Order Laguerre-Gauss Mode Generation and Interferometry for Gravitational Wave Detectors.</a> Physical Review Letters. 105, 231102 (2010).</li><li>Matsumoto, N., Ando, T., Inoue, T., Ohtake, Y., Fukuchi, N., Hara, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+high-quality+higher-order+Laguerre+Gaussian+beams+using+liquid-crystal-on-silicon+spatial+light+modulators.">Generation of high-quality higher-order Laguerre Gaussian beams using liquid-crystal-on-silicon spatial light modulators.</a> J. Opt. Soc. Am. 25, 1642-1651 (2008).</li><li>Kennedy, S. A., Szabo, M. J., Teslow, H., Porterfield, J. Z., Abraham, E. R. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Creation+of+Laguerre-Gaussian+laser+modes+using+diffractive+optics.">Creation of Laguerre-Gaussian laser modes using diffractive optics.</a> Physical Review A. 66, 043801 (2002).</li><li>Black, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+introduction+to+Pound-Drever-Hall+laser+frequency+stabilization.">An introduction to Pound-Drever-Hall laser frequency stabilization.</a> American Journal of Physics. 69, 79-87 (2001).</li><li>Freise, A., Heinzel, G., Lueck, H., Schilling, R., Willke, B., Danzmann, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frequency-domain+interferometer+simulation+with+higher-order+spatial.">Frequency-domain interferometer simulation with higher-order spatial.</a> Class.Quant.Grav. 21, (2004).</li><li>Uehara, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mode+cleaner+for+the+Initial+LIGO+10+Watt+Laser.">Mode cleaner for the Initial LIGO 10 Watt Laser.</a> LIGO internal report. 12, (1997).</li></ol>

Authors have nothing to disclose.

The output beams of most lasers used in high-precision measurements are designed to have a shape well described as a fundamental Gaussian mode. This particular beam geometry combines low diffraction with a spherical wave front. While the low diffraction is one of the key advantages of laser light, the spherical wave front is equally important, as it allows the low-loss transformation of the laser beam by standard optical components with spherical surfaces. Different beam shapes can be created as well, and recently Laguerre-Gauss beams have become of interest for their potential application in high-precision interferometry.
In this paper we demonstrated the experimental procedure to create higher-order Laguerre-Gauss modes with 95% purity for high-power, ultra stable laser beams. To achieve this, we have combined standard techniques from different aspects of optical research, namely diffractive phase plates and laser pre-stabilization to mode cleaner cavities. Our experiment provides a simple, modular and very reliable method to create high power beams in user defined higher-order modes. A commercial ultra-stable laser is used as the light source. Its output is injected to a diffractive phase plate, which can convert up to 75% of the light into the desired Laguerre-Gauss mode. This light is then injected to a small optical cavity and an electronic feedback loop is used to stabilize the laser frequency of the laser to the cavity length. The beam transmitted by the cavity is to 95% in the desired mode and, like the fundamental mode beam at the origin of the setup, has very good frequency stability at audio frequencies. All the parts represent standard components in modern optical experiments. We have successfully demonstrated this technique for laser powers up to 80 W pure Laguerre-Gauss 33 mode.
It could be possible to achieve similar results by replacing the phase plate with another mode-converting element (for example, other diffractive elements or astigmatic mode converters). Alternatively a laser could be setup with an optical resonator tuned for the desired Laguerre-Gauss modes, using for example, an amplitude mask. Finally the laser frequency stabilization to the reference optical cavity could be exchanged with a similar scheme that uses an atomic reference. The need for an electronic feedback system is probably the main disadvantage, but this is inevitable for any light source used for precision interferometer.
However, we believe that the method demonstrated in this paper provides a simple and modular scheme which can be scaled to all ranges of required laser frequency, power, or shape and thus presents a powerful and versatile method. Each part, the laser source, the diffractive element, as well as the optical cavity can be changed or optimized individually, which means that also existing laser injection systems can be upgraded to use Laguerre-Gauss modes.

在过去的几十年里，高精度干涉实验推向最终灵敏度制度量子效应开始发挥了决定性的作用。在这些目前和未来的实验，如激光冷却机械振荡器1，光学陷阱一代纠缠测试群众镜2，3，量子非拆迁干涉的4刚性腔5，稳频激光器，引力波探测6 ，7，8，研究人员正面临着许多限制基本面和技术面的噪声源。最严重的问题之一是谐振器反射镜的干涉的设置，这是造成由热激发的原子构成的反射镜基板和反射涂层的反射镜7，8，9的热噪声。这样的效果，也被称为布朗运动 ，将导致一个不确定性的相位反射光的任何测试的群众，所以会表现为根本干涉仪的输出噪声限制。例如，在项目设计先进的引力波天线，如高级，高级LIGO的处女座，和爱因斯坦望远镜的灵敏度是有限的这种类型的噪声最敏感的区域的观测频段10，11，12。 实验物理学家在社区努力做出持续的努力，以尽量减少这些噪声贡献，并提高他们的仪器的灵敏度。在镜子布朗噪声的特定情况下，缓解的一个方法是采用更大范围内的光束点的大小，因为目前使用的标准的基本HG 00束测试质量表面的更有效的表面的随机运动的更大范围内的平均束13，14。已经显示出扩展的反射镜的热噪声的功率谱密度逆高斯光束的大小的反射镜基板和镜子9平方成反比。然而，束斑变大时，较大部分的光功率丢失的反射面的边缘。如果使用比通常使用的HG 00束（见例如图1）的径向光强分布更均匀的光束， 布朗热噪声电平可以减小而不会增加这种类型的损失。在所有的更均匀的光束类型，已经提出了新版本的高精度的干涉，例如梅萨梁或圆锥形模式13，14，最有前途的是高阶LG与目前使用的球形光束由于其潜在的兼容性反射镜表面15。例如，二进制中子星螺旋系统的检出率 - 这被认为是最有前途的天体物理源第一毛重检测-离子约为系数2或更大的16上面的最小量的成本在目前正在建设10，11的第二代干涉仪的设计修改，可以增强。除了 ​​热噪声的好处，更广泛的高阶LG光束的强度分布（见，例如， 图2）已被证明，以减轻热像差的光学干涉仪内的幅度。这将减少热补偿系统在何种程度上依赖在未来的实验，以达到设计的敏感性19。 我们也调查，成功证明了可行性产生LG光束成功运作最好的灵敏度16，18，19，20，21，22 GW干涉所需的纯度和稳定性水平。该方法结合在不同的领域物理和光学齐全的开发技术和专业知识h为新一代的高稳定性，低噪声的单模激光束23，利用空间光调制器，衍射光学元件的操纵空间分布的光束18，22，24，25，26，和使用旨在进一步纯化和稳定的激光的光学谐振腔27的感测，控制和稳定化的先进技术。该方法已成功地证明，在实验室实验中，出口为测试在大型原型干涉仪20，用于产生在高的激光功率的LG模式高达80 W 21。在这篇文章中，我们提出高阶LG光束的方法的细节，并讨论所产生的光束的表征和验证的方法论。另外，在步骤4中概述了数值研究了一种用于与非完美反射镜19的空腔。

<table border="1">
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			<td>The experimental apparatus discussed in this paper requires the following types of instruments:</td>
		</tr>
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			<td></td>
			<td></td>
			<td></td>
			<td>Instrument</td>
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			<td>Solid state Laser source, Nd:YAG 1064 nm CW laser</td>
			<td></td>
			<td></td>
			<td>Quantity: 1</td>
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		<tr>
			<td>Faraday Isolator</td>
			<td></td>
			<td></td>
			<td>Quantity: 1</td>
		</tr>
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			<td>Electro-Optic Modulator (EOM)</td>
			<td></td>
			<td></td>
			<td>Quantity: 1</td>
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			<td>CCDcamera beam profiler</td>
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			<td></td>
			<td>Quantity: 1</td>
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			<td>Lenses</td>
			<td></td>
			<td></td>
			<td>Quantity: depending on apparatus design</td>
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			<td>Steering Mirrors</td>
			<td></td>
			<td></td>
			<td>Quantity: depending on apparatus design</td>
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			<td>Aperture</td>
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			<td></td>
			<td>Quantity: 1</td>
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			<td>High reflectivity mirrors (for normal incidence)</td>
			<td></td>
			<td></td>
			<td>Quantity: 2</td>
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			<td>Piezoelectric ring</td>
			<td></td>
			<td></td>
			<td>Quantity: 1</td>
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			<td>Cavity spacer</td>
			<td></td>
			<td></td>
			<td>Quantity: 1</td>
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			<td>Photodiodes and related control electronics</td>
			<td></td>
			<td></td>
			<td>Quantity: 1 or more, depending on apparatus design</td>
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			<td>Spatial light modulator</td>
			<td></td>
			<td></td>
			<td>Quantity: 1 
			Holoeye LCR-2500</td>
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			<td></td>
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			<td>All the above instruments are commercially available and no particular specification is required. We leave the choice of the most suitable instruments to the experimenter's discretion.</td>
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			<td></td>
			<td></td>
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			<td>For the interest of the experimenter interested in reproducing the protocol, we recommend the following tools used in our experiment:</td>
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			<td></td>
			<td></td>
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			<td>Tools</td>
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			<td>Innolight OEM 300NE, 1064 nm, 300 mW</td>
			<td></td>
			<td></td>
			<td>Laser Source:</td>
		</tr>
		<tr>
			<td>SIMTOOLs</td>
			<td></td>
			<td></td>
			<td>Software for data analysis, available at <a href="http://www.gwoptics.org/simtools/" target="_blank">www.gwoptics.org/simtools/</a></td>
		</tr>
		<tr>
			<td>FINESSE</td>
			<td></td>
			<td></td>
			<td>Software for optical simulations, <a href="http://www.gwoptics.org/finesse/" target="_blank"> www.gwoptics.org/finesse/</a></td>
		</tr>
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			<td></td>
			<td></td>
			<td></td>
			<td>Finally, the phase plate employed in the present experiment was manufactured by Jenoptik GmbH, based on a custom design provided by the Authors.</td>
		</tr>
	</tbody>
</table>

the generation of higher-order laguerre-gauss optical beams for high-precision interferometry

在高反射镜的热噪声是几种类型的高精度干涉实验，旨在达到标准量子极限或机械系统冷却到其量子基态的一个主要障碍。这是，例如预计将在最敏感的频段限制的情况下，未来的引力波观测站，其引力波信号的敏感性，通过原子振动镜群众。一所追求的有前途的方法来克服这个限制是采用高阶拉盖尔 - 高斯（LG）光束代替传统使用的基本模式。由于他们的更均匀的光强度分布的光束平均更有效地在热驱动的镜子，这反过来又降低了检测出的激光在反射镜的位置的不确定性的波动。 我们展示了一个有前途的方法来生成高阶LG光束的帮助下，衍射光学元件的一个基本的高斯光束整形。我们表明，与传统的传感和控制技术是已知的用于稳定基波激光束的高阶LG模可以被纯化，并稳定在一个相对较高的水平一样好。了一套诊断工具，使我们能够控制和定制生成的LG光束的属性。这使我们生产的LG电子束报告日期纯度最高。证明高阶LG干涉测量技术与标准和使用标准球面光学模式的兼容性，使得应用在下一代的高精度干涉他们的理想人选。

All the experimental results so far described in the text and shown in the figures constitute a representative example of a successful execution of the beam conversion protocol. The most representative result is the purity of the generated beam: a successful beam conversion should lead to a beam purity on the order of 95% or above. A good example of successful beam conversion is the measurement of the intensity profile of an 82.8 Watts, 96% pure LG33 beam obtained in 21 and here shown in Figure 12.
Similarly, as discussed in protocol sections, the mode conversion efficiencies of the phase plate and of the overall experimental setup are a good indicator of the successful design of the experimental apparatus, including the phase plate and the mode cleaner cavity. Values of order 50% to 60% and above are generally considered a good value for the mode conversion efficiency. The highest conversion efficiency reported so far with this type of setup is about 70% 21.
The simulation investigation described in Protocol Sec 4 should result in numbers for beam purity with realistic mirrors, suggested mirror specifications and the resulting beam purity when these specifications are adopted. An example of the results you can expect with realistic mirror maps are shown in 19 where an original LG33 purity of 89% is obtained, compared to a purity of &gt;99% for HG00. A purity of &gt;99% for the LG33 mode is achieved using specific mirror requirements with a major reduction of astigmatism in the mirror surface.
<img alt="Figure 1" src="/files/ftp_upload/50564/50564fig1.jpg" /> 
Figure 1. Intensity patterns for Hermite-Gauss (HG) modes up to order 6. The intensity patterns are normalized to have the same peak intensity, for visibility.
<img alt="Figure 2" src="/files/ftp_upload/50564/50564fig2.jpg" /> 
Figure 2. Intensity patterns for helical LG modes up to order 9. The intensity patterns are normalized to have the same peak intensity, for visibility.
<img alt="Figure 3" fo:conten-width="5in" fo:src="/files/ftp_upload/50564/50564fig3highres.jpg" src="/files/ftp_upload/50564/50564fig3.jpg" /> 
Figure 3. Sketch of a conventional setup for production and stabilization of HG00 beams.
<img alt="Figure 4" fo:conten-width="5in" fo:src="/files/ftp_upload/50564/50564fig4highres.jpg" src="/files/ftp_upload/50564/50564fig4.jpg" /> 
Figure 4. A sketch of the experimental setup discussed in this paper. The HG00 beam is first mode-matched to a desired waist size via a telescope then injected on the phase plate. The main diffracted beam is separated from the higher diffraction orders with an aperture and then sent to the Mode Cleaner cavity. A photodiode is used to extract the error signal for controlling the cavity length. The beam intensity is analyzed by a CCD camera.
<img alt="Figure 5" src="/files/ftp_upload/50564/50564fig5.jpg" /> 
Figure 5. Phase modulation profile to convert a HG00 mode to LG33 mode.
<img alt="Figure 6" src="/files/ftp_upload/50564/50564fig6.jpg" /> 
Figure 6. Example of blazed phase modulation profiles for generating LG33 modes.
<img alt="Figure 7" src="/files/ftp_upload/50564/50564fig7.jpg" /> 
Figure 7. Comparison between the intensity distribution of the composite beam generated by the phase plate (left) and the theoretical intensity distribution for a pure LG33 beam with same parameters.
<img alt="Figure 8" src="/files/ftp_upload/50564/50564fig8.jpg" /> 
Figure 8. Example of beam intensity profile fitting applied to a real LG33 beam transmitted from a phase plate (left) compared to fit results (center) and residuals of fit (right). <a href="https://www.jove.com/files/ftp_upload/50564/50564fig8large.jpg" target="_blank"> Click here to view larger figure</a>.
<img alt="Figure 9" fo:conten-width="4.5in" fo:src="/files/ftp_upload/50564/50564fig9highres.jpg" src="/files/ftp_upload/50564/50564fig9.jpg" /> 
Figure 9. Profile of an LG33 beam with Gaussian fit shown for comparison.
<img alt="Figure 10" fo:conten-width="4.5in" fo:src="/files/ftp_upload/50564/50564fig10highres.jpg" src="/files/ftp_upload/50564/50564fig10.jpg" /> 
Figure 10. Light power transmitted by a linear cavity as a function of the cavity length, when injecting a beam generated by the phase plate. The resonant peaks at 0 and 1 FSR correspond to the desired LG33 mode. A fit to this dominant mode is shown for comparison (blue line). The red curve shows the result of the numerical model, based on the modal content described in Table 2. Pictures of the unwanted beams to be filtered by the cavity are shown in the insets.
<img alt="Figure 11" fo:conten-width="5in" fo:src="/files/ftp_upload/50564/50564fig11highres.jpg" src="/files/ftp_upload/50564/50564fig11.jpg" /> 
Figure 11. An example of a mirror surface map for one of the Advanced LIGO optical mirrors 19.
<img alt="Figure 12" src="/files/ftp_upload/50564/50564fig12.jpg" /> 
Figure 12. Intensity profile of a 82.8 W LG33 beam transmitted by a linear cavity (left) compared with fit residuals (right).
<table border="1">
	<tbody>
		<tr>
			<td>p</td>
			<td>l</td>
			<td>0</td>
			<td>1</td>
			<td>2</td>
			<td>3</td>
			<td>4</td>
			<td>5</td>
			<td>6</td>
			<td>7</td>
			<td>8</td>
			<td>9</td>
		</tr>
		<tr>
			<td colspan="2">0</td>
			<td>1.0</td>
			<td>2.8</td>
			<td>1.7</td>
			<td>2.0</td>
			<td>2.2</td>
			<td>2.5</td>
			<td>2.6</td>
			<td>3.1</td>
			<td>3.0</td>
			<td>3.2</td>
		</tr>
		<tr>
			<td colspan="2">1</td>
			<td>1.7</td>
			<td>2.7</td>
			<td>2.2</td>
			<td>2.4</td>
			<td>2.6</td>
			<td>2.8</td>
			<td>2.9</td>
			<td>2.8</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td colspan="2">2</td>
			<td>2.2</td>
			<td>2.4</td>
			<td>2.5</td>
			<td>2.7</td>
			<td>2.9</td>
			<td>3.0</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td colspan="2">3</td>
			<td>2.5</td>
			<td>2.7</td>
			<td>2.8</td>
			<td>3.0</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td colspan="2">4</td>
			<td>2.9</td>
			<td>3.0</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>
Table 1. Optimum ratio between input HG00 beam size and LGpl phase image beam size for LG modes up to the order 9.
<table border="1">
	<tbody>
		<tr>
			<td>Mode</td>
			<td>LG33</td>
			<td>LG63</td>
			<td>LG43</td>
			<td>LG53</td>
			<td>LG32</td>
			<td>LG62</td>
		</tr>
		<tr>
			<td>Power</td>
			<td>75%</td>
			<td>8%</td>
			<td>4%</td>
			<td>4%</td>
			<td>4%</td>
			<td>1%</td>
		</tr>
	</tbody>
</table>
Table 2. Mode content analysis described by the cavity scan shown in Figure 10.

Watch this Scientific Journal Video about The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry at JoVE.com

The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry

Large laser-interferometers are being constructed to create a new type of astronomy based on gravitational waves. Their sensitivities, as for many other high-precision experiments, are approaching fundamental noise limits such as the atomic vibration of their components. We are pioneering technologies to overcome these limits using novel laser beam shapes.

代高阶拉盖尔 - 高斯光束的高精度干涉

Thermal noise in high-reflectivity mirrors is a major impediment for several  types of high-precision interferometric experiments that aim to reach the  ...

the-generation-higher-order-laguerre-gauss-optical-beams-for-high

Research

Education

JoVE Journal

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Physics

Engineering

Unit 1

Gravitation

SCIENTISTS IN ACTION

21.5K 次观看.  University of Birmingham. Large laser-interferometers are being constructed to create a new type of astronomy based on gravitational waves. Their sensitivities, as for many other high-precision experiments, are approaching fundamental noise limits such as the atomic vibration of their components. We are pioneering technologies to overcome these limits using novel laser beam shapes.

视频: The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

钮扣电池锂离子电池的建设和测试

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime.  Lithium ion ...

科研

工程学

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

制造超材料使用光纤拉丝法

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

纳米粒子的光学捕获

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

Bringing the Visible Universe into Focus with Robo-AO

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, &lambda;, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes - even telescopes with four times the diameter of HST - appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best.
Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images.
The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled1. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system2,3 employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope.

Light from astronomical objects must travel through the earth's turbulent atmosphere before it can be imaged by ground-based telescopes. To enable direct imaging at maximum theoretical angular resolution, advanced techniques such as those employed by the Robo-AO adaptive-optics system must be used.

将成为关注的焦点，可见的宇宙ROBO-AO

The angular  resolution of ground-based optical telescopes is limited by the degrading  effects of the turbulent atmosphere. In the absence of an ...

Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats &amp; Spheres

Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial shape (i.e., surface figure), will converge to final surface figure with excellent surface quality under a fixed, unchanging set of polishing parameters in a single polishing iteration. In contrast, conventional full aperture polishing methods require multiple, often long, iterative cycles involving polishing, metrology and process changes to achieve the desired surface figure. The Convergent Polishing process is based on the concept of workpiece-lap height mismatch resulting in pressure differential that decreases with removal and results in the workpiece converging to the shape of the lap. The successful implementation of the Convergent Polishing process is a result of the combination of a number of technologies to remove all sources of non-uniform spatial material removal (except for workpiece-lap mismatch) for surface figure convergence and to reduce the number of rogue particles in the system for low scratch densities and low roughness. The Convergent Polishing process has been demonstrated for the fabrication of both flats and spheres of various shapes, sizes, and aspect ratios on various glass materials. The practical impact is that high quality optical components can be fabricated more rapidly, more repeatedly, with less metrology, and with less labor, resulting in lower unit costs. In this study, the Convergent Polishing protocol is specifically described for fabricating 26.5 cm square fused silica flats from a fine ground surface to a polished ~&#955;/2 surface figure after polishing 4 hr per surface on a 81 cm diameter polisher.

A novel optical polishing process, called &#8220;Convergent Polishing&#8221;, which enables faster, lower cost polishing, is described. Unlike conventional polishing processes, Convergent Polishing allows a glass workpiece to be polished in a single iteration and with high surface quality to its final surface figure without requiring changes to polishing parameters.

收敛抛光：高品质光学平面与球的一种简单，快速，全口径抛光工艺

Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

通过光学吸收跃迁图案 - 制备与表征

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

Writing Bragg Gratings in Multicore Fibers

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

We describe a technique for inscribing identical fiber Bragg gratings into each core of a multicore fiber. This is achieved by introducing an additional surface into the optical path to mitigate lensing by the curved surface of the fiber cladding.

写布拉格光栅在多核纤维

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong ...

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

We present a compact reflection digital holographic system (CDHM) for inspection and characterization of MEMS devices. A lens-less design using a diverging input wave providing natural geometrical magnification is demonstrated. Both static and dynamic studies are presented.

紧凑的镜头少数字全息显微镜的MEMS检测与表征

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and ...

Scanning Light Scattering Profiler (SLPS) Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

The scanning light scattering profiler (SLSP) methodology has been developed for the full-angle quantitative evaluation of forward and backward light scattering from intraocular lenses (IOLs) using goniophotometer principles. This protocol describes the SLSP platform and how it employs a 360&#176; rotational photodetector sensor that is scanned around an IOL sample while recording the intensity and location of scattered light as it passes through the IOL medium. The SLSP platform can be used to predict, non-clinically, the propensity for current and novel IOL designs and materials to induce light scatter. Non-clinical evaluation of light scattering properties of IOLs can significantly reduce the number of patient complaints related to unwanted glare, glistening, optical defects, poor image quality, and other phenomena associated with the unintended light scattering. Future studies should be conducted to correlate SLSP data with clinical results to help identify which measured light scatter is most problematic for patients that have undergone cataract surgery subsequent to IOL implantation.

Scanning Light Scattering Profiler SLPS Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

This protocol describes the scanning light scattering profiler (SLSP) that enables the full-angle quantitative evaluation of forward and backward scattering of light from intraocular lenses (IOLs) using goniophotometer principles.

基于扫描光散射分析器（SLPS）的方法来量化评估来自眼内镜的前向和后向光散射

The scanning light scattering profiler (SLSP) methodology has been developed for the full-angle quantitative evaluation of forward and backward light ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.