笔者想感谢基督教Olivier和菲利普·克雷蒂安对有关电子有价值的帮助，埃里克吉拉德在GIGA概念公司与电动偏振控制器的支持，真正的教授为河谷商业旋光仪教授米歇尔Piché的贷款为许多富有成效的讨论。 自然等技术（FRQNT）中，加拿大自然科学和工程研究理事会（NSERC）和加拿大暑期工作 - 这项工作是由全宗德RECHERCHE魁北克的支持。

1.建立一个光纤ML光纤激光器，包括电动PSC <ol><li>收集以下组件：单模掺铒光纤，一个980 / 1,550nm处波分复用器（WDM），一个980 / 1,550nm处的WDM-1,550nm处隔离混合组件，50/50光纤耦合器，一个光纤偏振器，机动化的PSC，二980nm的激光泵浦二极管，一个99/1光纤耦合器和手动联的PSC。 </li><li>切断掺铒光纤和所有其他光纤尾纤组件，以适应与所需腔设计。 注：所提出的自动化方法适用于基于非线性偏振旋转光纤激光器。它应为不同的操作机制工作，如孤子激​​光器，展宽脉冲激光，耗散孤子激光器和similariton激光。后者政权在该实验中使用。 </li><li>要构建激光腔，利用光纤熔接加入腔体组件的图（ 图3显示的顺序&lt;/ STRONG&gt;）。执行每个熔接之前，清洁纤维用异丙醇终止，并用光纤切割刀切割它们。 注意：激光的内部组件，在环形腔，机动PSC顺时针顺序，一个980 / 1,550nm处的WDM中，掺铒光纤，一个980 / 1,550nm处的WDM隔离混合组件，50/50输出耦合器和光纤偏振器。外部元件是一个99/1光纤耦合器和手动联的PSC（如在步骤1.7和1.8中讨论）。 注：的约为30厘米的纤维段必须在机动PSC插入的接头与所述腔体的其他组件执行之前。虽然一个标准单模光纤将工作，建议该段使用聚酰亚胺涂覆的纤维，因为它是由控制器的螺钉所施加的压力更耐并因此将持续较长时间。 </li><li>加入泵浦激光二极管使用熔接机的波分复用器。同样，清洁纤维与异人结束cohol，履行各自熔接前，用光纤切割刀切割它们。 </li><li>激光二极管连接到各自的温度控制器和最新的驱动程序。 </li><li>所述腔内机动瑶型光纤挤压PSC（ 图4）连接到它的驱动模块，然后将驱动模块连接到计算机的USB端口。 注意：此端口由数字“COM4”确定为显示在计算机的“设备管理器”。 </li><li>在激光的输出， 即在50/50耦合器的端口尚未剪接，剪接一个99/1耦合器。 注：99％的端口是可用输出。的1％端口用于监视自动化过程中的偏光状态。 </li><li>插入沿1％端口的纤维手动PSC。要做到这一点，拧开螺丝，打开PSC。将光纤在适当的插槽，然后把螺丝放回孔，拧他们进来。 </li><li>拼接角打磨纤维有限公司nnector（APC）在1％端口光纤（手动PSC之后）的末尾。在进行熔接前，清洁和切割光纤结束。 </li><li> 99％的输出连接到使用裸光纤适配器光谱分析仪（OSA）。 注：如稍后所讨论的，看到的在OSA光谱将为检查如果激光是ML的替代方式。 </li><li>用聚酰亚胺膜带保护所有的纤维和成分在空腔正常。 注：纤维和部件必须从在任何条件下移动地防止如当表振动或风扇吹空气。的聚酰亚胺薄膜带是为了避免损坏纤维使用。 </li><li>拧紧腔内PSC的压力螺丝，直到纤维开始略有挤压。 </li><li>打开泵激光器二极管和由激光二极管制造商指定调整其电流为它们的最大值。 </li><li>启动仪器通讯接口。在“每ipherals和接口“在左边栏中，选择”COM4“，点击”打开VISA测试面板“，点击”输入/输出“，然后在”选择或输入命令“式的”SM，500,3000 n“然后点击“查询”按钮，这个命令PSC 3000人步骤顺时针方向0.1125°旋转。尽管这样，PSC到达机械停止。 </li><li>在“COM4”测试面板中，键入“SM，500，-10 N”的“选择或输入命令”，然后点击“查询”按钮。力晶然后旋转约100°逆时针。检查是否通过观察在OSA的光谱达到ML。当全宽光谱的半值是几十纳米的（ 图5）的顺序到达的ML。如果达到ML，保持双折射和固定角度和转到步骤1.18。 </li><li>如果未达到ML，重复1.15直到ML或最大角度attai达到nable与PSC。 </li><li>如果达到所述PSC的最大角度的ML发生之前，通过稍微拧紧压力螺丝增加PSC的双折射，并根据需要对得到的ML重复步骤1.14，1.15和1.16多次。 </li><li>一旦达到ML，降低泵的权力，他们的最小值，允许ML到自启动。这样做，减小泵功率，直到ML会丢失。然后，把他们带回慢慢的走向，这将使ML重新出现的最小值。关闭水泵关闭并重新上本身如果激光模式锁定检查。增加泵浦功率略微更加确保对ML是稳定的，并会每个激光被接通时的自启动。 </li></ol> 2.分析输出信号的偏振<ol><li> 1％的抽头链接到一个商业旋光仪。 </li><li>旋光仪连接使用USB端口的计算机。 </li><li>在“选择或输入命令”中的“COM4”测试面板，TYPE“SM，500,3000 n”，然后点击“查询”按钮。 </li><li>运行商用偏振控制软件，并通过点击“Start”按钮开始极化测量。 </li><li>在“COM4”测试面板中，键入“SM，500，-10 N”的“选择或输入命令”，然后点击“查询”按钮。观察对偏振极化状态。 </li><li>重复步骤2.5根据需要覆盖由腔内PSC允许角度的整个范围多次。观察该偏振状态，除了在哪里ML达到如通过同时观看在OSA的光谱的宽度可以看出，特定的角度的角度变化非常顺利。 </li><li>重复步骤2.3至2.6，但这个时候，而不是仅仅看偏振态，记录斯托克斯参数值S 1，S 2和S 3的功能所述PSC的角度秒（ 图6）。要清楚地看到这些值，选择“测量- →示波器”，在软件的菜单，查找S 1，S 2和S 3的平均值。同时观看光谱并记录其中激光是ML的角度。 </li></ol> 3.建立一个反馈回路实现自动化PSC的对齐使用商业测量光仪<ol><li>关闭计算机。 </li><li>商业旋光仪的串行端口连接到计算机的串行端口“COM1”。重新启动计算机，旋光仪。 </li><li>启动图形化编程语言界面（GPLI），将允许通过“COM1”，并通过“COM4”电动PSC的控制旋光仪的读数。 </li><li>在GPLI，点击“空白VI”。然后，选择“窗口→瓦左右。“ 注：屏幕然后将两部分进行分割。框图被显示在右边。它被用来创建使用具有不同的图标相关联的不同功能的脚本。前面板显示在左侧。它被用于显示命令和当脚本运行测量。 </li><li>在GPLI的程序框图窗口，发展ML自动化脚本与商业旋光仪使用（ 见图7）。 注：此脚本从偏振读取S1和使用它的值来提供反馈，并达到PSC角度导致ML的正确对齐。 ML的检测是通过作为角度是变化的搜索S中1的变形例的不连续性来实现。 注意：用于通过“COM4”来控制所述PSC的命令中的相同的步骤2.3和2.5给出的那些。该命令阅读S 1 </在通过“COM1”商业偏光子&gt;为“* SOP吗？ n”。 </li><li>点击“文件→保存”保存脚本，然后通过点击“→”键运行它。所述PSC被带回到其机械停止，然后将其旋转以约1°至ML步骤达到，表示S1的，因为它的发展的值。 </li></ol> 4.建立一个简陋的自制偏振分析器<ol><li>连接示波器使用GPIB接口的电脑。 </li><li>把偏振分光器立方体（PBS）的光学台上。 </li><li>设置了三个FC / APC光纤端口准直器与PBS（ 图8）。 注意：其中一个端口为输入。另外两个是用于信号的x和y偏振分量的输出。 </li><li>纤维尾纤的InGaAs PIN光电二极管连接到第一输出。 </li><li>光电二极管连接到反式impedaNCE电路（ 图9）。 </li><li>连接电路的电输出到示波器的通道1。 </li><li>转跨阻抗电路上。 </li><li>在GPLI，通过使用命令GPIB接口读取示波器的通道1的电压的平均值“：IMM：MEASU SOU CH1;”选择示波器的通道1，“MEASU：IMM：TYPE均值;”以定义测量是一个平均电压，“MEASU：IMM：VAL”来获取值，最后“MEASU：IMM：UNI？”获得的测量单位。点击“文件→保存”保存脚本，然后通过点击“→”键运行它。 </li><li>激光器的输出的1％连接在PBS中的输入端口，并打开激光器上以任意的泵浦功率。此发送一个1550nm波长的光信号到输入。 </li><li>测量在第一输出上的平均电压。然后，断开光纤尾纤光电二极管和替换它由商业电表。测量在此输出的光功率。 </li><li>重复步骤4.10，同时改变所述输入光信号的功率。电压应与光功率线性变化。发现此线性关系的系数。 注：这种关系将在步骤4.20被用于从测得的电压获取P X [。 </li><li>第二光纤尾纤的InGaAs PIN光电二极管连接到PBS中的第二输出。 </li><li>光电二极管连接到一第二跨阻抗电路。 </li><li>连接电路的电输出到示波器的通道2。 </li><li>转跨阻抗电路上。 </li><li>在GPLI，通过使用命令GPIB接口读取示波器通道2的电压的平均值“：IMM：MEASU SOU CH2;”选择示波器的通道2，“MEASU：IMM：TYPE均值;”以定义测量是一个平均电压，“MEASU：IMM：VAL？4;来获取值，最后“MEASU：IMM：UNI？”获得的测量单位。点击“文件→保存”保存脚本，然后通过点击“→”键运行它。 </li><li>打开激光上任意泵浦功率。 </li><li>测量在第二输出上的平均电压。然后，断开光纤尾纤光电二极管和商用电表更换。测量在此输出的光功率。 </li><li>重复步骤4.18，同时改变所述输入光信号的功率。确保电压与光功率线性变化。 注：找到该线性关系的系数。这种关系将在步骤4.20被用于从测得的电压获取P Y [。 </li><li>设立第二个探测器测量P Y [之后，使用GPLI计算定义为S = 1的第一个斯托克斯参数S 1（ <eM&gt; P X [ - P Y）/（P X + P Y [）。自制的简陋偏器现在可以使用了。 </li></ol> 5.国产偏振仪自动化过程中更换商业旋光仪<ol><li>连接激光自制检偏器的输入输出的1％（如在步骤4.9完成）。 </li><li>通过使用自制的偏振分析仪（而不是商业旋光）重复步骤2.7测量第一斯托克斯参数S 1作为对PSC（ 图10）的角度的函数。观察第 1条曲线在每一步自动更新。观察在S1的值的不连续跳跃时的ML发生时（这是在使用商用光仪的情况下）。 注：使用GPLI脚本来执行此任务自动售货机ically。该脚本是基于一个循环，通过1°步骤改变所述PSC的角（使用命令“SM，500，-10 N”发送到“COM4”），并从自制读出S1的值偏振分析器在每一个步骤。 </li><li>修改在3.5，使开发的，而不是使用由商业偏振给定的值时，脚本，它得到从自制偏振分析器P X [和P y，然后计算的 1 =（P X [-P Y）/（P X + P Y [）。 </li><li>使用基于自制偏振分析器新脚本，以类似于步骤3.6的方式自动毫升激光器。 </li></ol>

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已经表明，有可能通过使用基于输出偏振测量的反馈回路来自动NPR光纤环形激光器的ML。为了实现这一任务，关键的是要插入在空腔的可调节的P​​SC。腔的输出耦合器必须只偏振片之前位于以看到一个CW信号的极化状态与一个脉冲信号（ 图2）之间的差。所述PSC的双折射必须预先调整，使ML可以发现和泵功率必须为了得到在空腔的单脉冲，并尽量减少可能发生的竞争机制的数目被设置...

本文的目的是提出一种自动化校准过程来获得非线性偏振旋转光纤激光器模式锁定（ML）。这个过程是基于两个基本步骤：通过测量激光器的输出信号的偏振，然后设置向上的自启动控制系统，以获得到ML检测ML制度。 光纤激光器已经成为时下光学的重要工具。它们是相干的近红外光的有效源和它们现在延伸到所述电磁光谱的中红外部分。其成本低，易于使用都使得他们有吸引力的替代相干光的其它来源，例如固态激光器。光纤激光器也能提供超短脉冲（100 FSEC或更小）时，ML机构被插在纤维空腔中。有许多方法来设计这种ML机制如非线性循环反射镜和可饱和吸收器。其中之一，广泛使用˚F或它的简单性，基于所述信号1,2的非线性偏振旋转（NPR）。它使用的信号的极化椭圆经历旋转正比于它的强度，因为它在激光腔中的纤维中传播的事实。通过在空腔中插入一个偏振器，本NPR的信号的往返过程中导致依赖于强度的损失。 激光然后可以通过控制偏振状态被强制ML。有效地，信号的高功率部分将经受降低损失（ 图1），这最终将导致光的超短脉冲的形成时的激光被接通和从低功率噪声信号开始。然而，这种方法的缺点是，偏振状态控制器（PSC）必须正确对齐获得的ML。通常，操作者通过用快纵改变PSC的位置和分析激光的输出信号手动发现对MLhotodiode，光频谱分析仪或一非线性光学自相关器。一旦被检测到的脉冲的发射时，操作者停止改变所述PSC的位置，因为激光是ML。显然，获得激光自启动自动导致效率的重要收获。这是特别真实当激光受扰动改变取向或空腔配置，因为操作者必须一次次经过对齐过程。在过去十年中，不同的方法已经被提出来实现这种自动化。海尔威格等 3中使用压电榨汁控制在组合偏振与信号的极化状态的具有分裂振幅的-全光纤光仪检测ML全面分析。 Radnarotov 等 4中使用的液晶板的PSCs基于所述RF频谱检测ML的分析。 Shen等人 5中使用压电榨汁控制偏振和光电二极管/高速计数器系统来检测的ML。最近，提出根据一种进化算法的策略，其中所述检测是通过一个高带宽的光电二极管与一个intensimetric二阶自相关器和一个光学频谱分析仪提供组合。控制然后与空腔6内的两个电子驱动的PSCs进行。 本文介绍的检测ML并将其应用到自动化技术迫使光纤激光器ML的创新方式。激光的ML的检测是通过分析作为所述PSC的角度被扫过的信号的输出偏振状态如何变化来实现的。如将要示出，到ML的过渡与在偏振态通过测量输出信号的斯托克斯参数的一个可检测一个突然的变化相关联。一个事实，即脉冲比CW信号越强，将进行更重要的NPR EXPlains这种变化。由于激光的输出立即位于空腔中的偏振器之前，在该位置的脉冲的偏振状态是由一个CW信号的偏振状态（ 图2）不同，将用于鉴别对ML状态。这个过程，它的第一个实验实现的理论方面奥利弗等人作了介绍。7。在这篇文章中，重点将放在程序，它的局限和自身优势的技术方面。 这种技术是实现相对简单，并且不需要复杂的测量仪器来检测ML状态并自动激光的对准来获得的ML。通过可编程接口可调外使用PSC是必需的。不同的PSCs可以在原则上可以使用：压电榨汁，液晶，由电动机，磁光晶体或机动的全光纤PSC基于ö旋转波片ñ挤压和扭曲纤维8。在这篇文章中，后者被使用，全光纤机动姚明型PSC。以检测的偏振状态的昂贵的商业偏振都可以使用。然而，由于只需要第一斯托克斯参数的值，在组合偏振分束器与两个光电二极管将足以所示在这篇文章。 所有这些组件是廉价的广泛使用的掺铒光纤激光器。基于此过程的反馈回路可以在几分钟内找到的ML。这个反应时间是合适的光纤激光器的大多数应用是相媲美的其它现有技术。实际上，响应时间是由用于分析的信号的极化电子的限制。最后，虽然该过程这里施加到similariton 9掺铒光纤激光器，它可以立即用于任何基于NPR的光纤激光器作为上述设备或其equivalen吨在感兴趣的波长变得可用。

<table border="0" cellpadding="0" cellspacing="0" width="903">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Bare-Fiber adaptor</td>
			<td style="width:163px;">Bullet</td>
			<td style="width:183px;">NGB-14</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:391px;">Drop-in polarization controller</td>
			<td style="width:163px;">General Photonics Corp.</td>
			<td style="width:183px;">Polarite PLC-006</td>
			<td>Manual polarization controller.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:391px;">DSP In-line polarimeter</td>
			<td style="width:163px;">General Photonics Corp.</td>
			<td style="width:183px;">POD-101D PolaDetect</td>
			<td>Polarimeter with USB/serial computer connectivity.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Fiber Cleaver</td>
			<td style="width:163px;">Fitel</td>
			<td style="width:183px;">S323</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">FiberPort</td>
			<td style="width:163px;">Thorlabs Inc.</td>
			<td style="width:183px;">PAF-X-2-C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Fixed Fiber-to-Fiber Coupler Bench</td>
			<td style="width:163px;">Thorlabs Inc.</td>
			<td style="width:183px;">FBC-1550-APC</td>
			<td>Any optical bench could be used. A 3-way bench would even be better.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Fusion Splicer</td>
			<td style="width:163px;">Fujikura</td>
			<td style="width:183px;">FSM-40PM</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">High resolution all fiber polarization controller</td>
			<td style="width:163px;">Giga Concept Inc.</td>
			<td style="width:183px;">GIG-2201-1300</td>
			<td>All-fiber motorized polarization controller with USB computer connectivity.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">InGaAs PIN PD module</td>
			<td style="width:163px;">Optoway</td>
			<td style="width:183px;">PD-1310</td>
			<td>Pigtailed photodiode.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Instrument communication interface</td>
			<td style="width:163px;">National Instruments</td>
			<td style="width:183px;">NI MAX</td>
			<td>It comes packaged with National Instruments drivers (NI-VISA, NI-DAQmx, etc.)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Operational amplifier</td>
			<td style="width:163px;">Texas Instruments</td>
			<td style="width:183px;">TLO81ACP</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Optical Powermeter</td>
			<td style="width:163px;">Newport</td>
			<td style="width:183px;">818-IS-1 with 1835-C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Optical spectrum analyzer</td>
			<td style="width:163px;">Anritsu</td>
			<td style="width:183px;">MS9710C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Oscilloscope</td>
			<td style="width:163px;">Tektronix</td>
			<td style="width:183px;">TDS2022</td>
			<td>Oscilloscope with GPIB computer connectivity.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Polarizing beamsplitter module</td>
			<td style="width:163px;">Thorlabs Inc.</td>
			<td style="width:183px;">PSCLB-VL-1550</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Polyimide Film Tape</td>
			<td style="width:163px;">3M</td>
			<td style="width:183px;">5413</td>
			<td>Tape to fix the components on the table without damaging the fibers.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Graphical programming language interface (GPLI)</td>
			<td style="width:163px;">National Instruments</td>
			<td style="width:183px;">LabVIEW</td>
			<td>Interface to program in G Programming Language and communicate with laboratory instruments.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:391px;">Polarimeter controlling software</td>
			<td style="width:163px;">General Photonics Corp.</td>
			<td style="width:183px;">PolaView</td>
			<td>Comes with the polarimeter General Photonics POD-101D.</td>
		</tr>
	</tbody>
</table>

automation of mode locking in a nonlinear polarization rotation fiber laser through output polarization measurements

当激光是锁模，它发射由激光腔长度来确定的重复率超短脉冲序列。本文概述了新的和廉价的步骤来强制模式锁定在预调节非线性偏振旋转光纤激光器。当锁模发生此程序是基于该检测输出偏振状态的突然变化的。这种变化被用来命令腔内偏振控制器的取向，以便找到锁模条件。更具体地，当偏振控制器的角度被横扫第一斯托克斯参数的值而变化，而且，当激光进入锁模状态它经历了一个突然变化。监控这个突然变化提供了可以用来命令偏振控制器的取向和驱动朝模式锁定激光器的实用易于检测信号。这种监测是通过将一小部分来实现该信号的偏振分析仪测量第一斯托克斯参数。当激光进入锁模状态将发生在读出此参数的来自分析器的突然改变。在这一刻，该偏振控制器的所需角度保持固定。对准完成。此过程提供了一个替代的方式来使用的设备，如一个光学频谱分析仪，一个RF频谱分析仪，连接到电子脉冲计数器或基于双光子吸收或产生二次谐波的非线性检测方案的光电二极管的现有自动化程序。它适用于由非线性偏振旋转锁定激光器模式。这是比较容易实现，它需要廉价的方法，尤其是在1550nm的波长，它降低相比于上述技术产生的生产和运行成本。

NPR锁模光纤激光器是已知的，以提供大量的各种脉冲制度如Q-开关脉冲10，相干ML脉冲，类噪声脉冲，ML脉冲束缚态，谐波ML和相互作用ML脉冲11的复杂的结构。在这里所描述的激光，所述PSC的双折射后固定为能够得到ML，泵浦功率调整为相对接近单脉冲ML的阈值。在这样做时，竞争制度的数量减少到最低限度。在这个泵功率并根据PSC的角度，提出了激光不同?...

Watch this Scientific Journal Video about Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements at JoVE.com

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

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 ...

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11.3K 次观看.  Université Laval. 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.

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

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing technology is used to fabricate particles with slender arms connected at a common center. Shapes explored are crosses (two perpendicular rods), jacks (three perpendicular rods), triads (three rods in triangular planar symmetry), and tetrads (four arms in tetrahedral symmetry). Methods for producing on the order of 10,000 fluorescently dyed particles are described. Time-resolved measurements of their orientation and solid-body rotation rate are obtained from four synchronized videos of their motion in a turbulent flow between oscillating grids with R&#955; = 91. In this relatively low-Reynolds number flow, the advected particles are small enough that they approximate ellipsoidal tracer particles. We present results of time-resolved 3D trajectories of position and orientation of the particles as well as measurements of their rotation rates.

We use 3D printing to fabricate anisotropic particles in the shapes of jacks, crosses, tetrads, and triads, whose alignments and rotations in turbulent fluid flow can be measured from multiple simultaneous video images.

测量的方向和旋转速率方法3D打印在湍流颗粒

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing ...

科研

工程学

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

不锈钢滑面的制备及高温抗粘接性能研究

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

静态和扫描模式下中子伽马分析法测量土壤碳

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...

Ultrasonic Fatigue Testing in the Tension-Compression Mode

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. It is also used to simulate loading of material during operation in high speed conditions, such as those experienced by components of jet engines or car turbo pumps. It is necessary to operate only in the high and ultra-high cycle region, due to the possibility of extremely high deformation rates, which can have a significant influence on the test results. Specimen shape and dimensions have to be carefully selected and calculated to fulfill the resonance condition of the ultrasonic system; thus, it is not possible to test the full components or specimens of arbitrary shape. Before each test, it is necessary to harmonize the specimen with the frequency of the ultrasonic system to compensate for deviations of the real shape from the ideal one. It is not possible to run a test until a total fracture of the specimen, since the test is automatically terminated after initiation and propagation of the crack to a certain length, when the stiffness of the system changes enough to shift the system out of the resonance frequency. This manuscript describes the process of evaluation of materials' fatigue properties at high-frequency ultrasonic fatigue loading with use of mechanical resonance at a frequency close to 20 kHz. The protocol includes a detailed description of all steps required for a correct test, including specimen design, stress calculation, harmonizing with the resonance frequency, performing the test, and final static fracture.

A protocol for ultrasonic fatigue testing in the high and ultra-high cycle region in axial tension-compression loading mode.

拉伸压缩模式下的超声疲劳试验

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser (laser-SARPES), and demonstrate a power of this technique for studying solid state physics. Laser-SARPES achieves two great capabilities. Firstly, by examining orbital selection rule of linearly polarized lasers, orbital selective excitation can be carried out in SAPRES experiment. Secondly, the technique can show full information of a variation of the spin quantum axis as a function of the light polarization. To demonstrate the power of the collaboration of these capabilities in laser-SARPES, we apply this technique for the investigations of spin-orbit coupled surface states of Bi2Se3. This technique affords to decompose spin and orbital components from the spin-orbit coupled wavefunctions. Moreover, as a representative advantage of using the direct spin detection collaborated with the polarization-variable laser, the technique unambiguously visualizes the light polarization dependence of the spin quantum axis in three-dimension. Laser-SARPES dramatically increases a capability of photoemission technique.

Here, we combine polarization-variable 7-eV laser with spin- and angle-resolved photoemission technique to visualize the spin-orbital coupling effect in solid states.

自旋角分辨光电子光谱与偏振变激光相结合的实验方法

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser ...

Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due to their potential applications for future device technologies such as sensors and storage. However, conventional approaches, which usually utilize materials containing magnetic metal ions (or radicals), have a major problem: only a few materials have been found to show the coupling phenomena at room temperature. Recently, we proposed a new approach to achieve room-temperature magnetoelectrics. In contrast to conventional approaches, our alternative proposal focuses on a completely different material, a &#34;liquid crystal&#34;, free from magnetic metal ions. In such liquid crystals, a magnetic field can be utilized to control the orientational state of constituent molecules and the corresponding electric polarization through magnetic anisotropy of the molecules; it is an unprecedented mechanism of the magnetoelectric effect. In this context, this paper provides a protocol to measure ferroelectric properties induced by a magnetic field, that is, the direct magnetoelectric effect, in a liquid crystal. With the method detailed here, we successfully detected magnetically-tuned electric polarization in the chiral smectic C phase of a liquid crystal at room temperature. Taken together with the flexibility of constituent molecules, which directly affects the magnetoelectric responses, the introduced method will serve to allow liquid crystal cells to acquire more functions as room-temperature magnetoelectrics and associated optical materials.

In this report, we present a protocol to examine direct magnetoelectric effects, i.e., induction of ferroelectric polarization by applying magnetic fields, in liquid crystals. This protocol provides a unique approach, supported by the softness of liquid crystals, to achieve room-temperature magnetoelectrics.

液晶中磁调谐铁电极化的测量

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due ...

Carrier Lifetime Measurements in Semiconductors through the Microwave Photoconductivity Decay Method

This work presents a protocol employing the microwave photoconductivity decay (&#956;-PCD) for measurement of the carrier lifetime in semiconductor materials, especially SiC. In principle, excess carriers in the semiconductor generated via excitation recombine with time and, subsequently, return to the equilibrium state. The time constant of this recombination is known as the carrier lifetime, an important parameter in semiconductor materials and devices that requires a noncontact and nondestructive measurement ideally achieved by the &#956;-PCD. During irradiation of a sample, a part of the microwave is reflected by the semiconductor sample. Microwave reflectance depends on the sample conductivity, which is attributed to the carriers. Therefore, the time decay of excess carriers can be observed through detection of the reflected microwave intensity, whose decay curve can be analyzed for estimation of the carrier lifetime. Results confirm the suitability of the &#956;-PCD protocol in measuring the carrier lifetime in semiconductor materials and devices.

As one of the important physical parameters in semiconductors, carrier lifetime is measured herein via a protocol employing the microwave photoconductivity decay method.

微波导光衰减法测量半导体中的载波寿命

This work presents a protocol employing the microwave photoconductivity decay (&#956;-PCD) for measurement of the carrier lifetime in semiconductor ...

Implementation of a Nonlinear Microscope Based on Stimulated Raman Scattering

Stimulated Raman scattering (SRS) microscopy uses near-infrared excitation light; therefore, it shares many multi-photon microscopic imaging properties. SRS imaging modality can be obtained using commercial laser-scanning microscopes by equipping with a non-descanned forward detector with proper bandpass filters and lock-in amplifier (LIA) detection scheme. A schematic layout of a typical SRS microscope includes the following: two pulsed laser beams, (i.e., the pump and probe directed in a scanning microscope), which must be overlapped in both space and time at the image plane, then focused by a microscope objective into the sample through two scanning mirrors (SMs), which raster the focal spot across an x-y plane. After interaction with the sample, transmitted output pulses are collected by an upper objective and measured by a forward detection system inserted in an inverted microscope. Pump pulses are removed by a stack of optical filters, whereas the probe pulses that are the result of the SRS process occurring in the focal volume of the specimen are measured by a photodiode (PD). The readout of the PD is demodulated by the LIA to extract the modulation depth. A two-dimensional (2D) image is obtained by synchronizing the forward detection unit with the microscope scanning unit. In this paper, the implementation of an SRS microscope is described and successfully demonstrated, as well as the reporting of label-free images of polystyrene beads with diameters of 3 &#181;m. It is worth noting that SRS microscopes are not commercially available, so in order to take advantage of these characteristics, the homemade construction is the only option. Since SRS microscopy is becoming popular in many fields, it is believed that this careful description of the SRS microscope implementation can be very useful for the scientific community.

In this manuscript, the implementation of a stimulated Raman scattering (SRS) microscope, obtained by the integration of an SRS experimental set-up with a laser scanning microscope, is described. The SRS microscope is based on two femtosecond (fs) laser sources, a Ti-Sapphire (Ti:Sa) and synchronized optical parametric oscillator (OPO).

基于刺激拉曼散射的非线性显微镜的实现

Stimulated Raman scattering (SRS) microscopy uses near-infrared excitation light; therefore, it shares many multi-photon microscopic imaging properties. ...

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

We present a high-performance source of unconditional polarization-entangled photons that have a high-emission rate, a broadband distribution, are degenerated and postselection free. The property of the source is based on the multiple quantum interference effect with a round-trip configuration of a Sagnac interferometer. The quantum interference effects make it possible to use the high generation efficiency of the polarization-entangled photons to process parametric down-conversion, and separate degenerated photon pairs into different optical modes without a postselection requirement. The principle of the optical system was described and experimentally used to measure the fidelity and Bell parameters, and also to characterize the generated polarization-entangled photons from a minimum of six combinations of polarization correlated data. The experimentally obtained fidelity and Bell parameters exceeded the classical local correlation limit and are clear evidence of the generation of unconditional polarization-entangled photons.

We describe an optical system for the generation of unconditional polarization-entangled photons based on multiple quantum interference effects with a detection scheme to estimate the experimental fidelity of generated entangled photons.

基于多重量子干扰生成无条件极化纠缠光子的光子系统

We present a high-performance source of unconditional polarization-entangled photons that have a high-emission rate, a broadband distribution, are ...

Low-cost Custom Fabrication and Mode-locked Operation of an All-normal-dispersion Femtosecond Fiber Laser for Multiphoton Microscopy

A protocol is presented to build a custom low-cost yet high-performance femtosecond (fs) fiber laser. This all-normal-dispersion (ANDi) ytterbium-doped fiber laser is built completely using commercially available parts, including $8,000 in fiber optic and pump laser components, plus $4,800 in standard optical components and extra-cavity accessories. Researchers new to fiber optic device fabrication may also consider investing in basic fiber splicing and laser pulse characterization equipment (~$63,000). Important for optimal laser operation, methods to verify true versus apparent (partial or noise-like) mode-locked performance are presented. This system achieves 70 fs pulse duration with a center wavelength of approximately 1,070 nm and a pulse repetition rate of 31 MHz. This fiber laser exhibits the peak performance that may be obtained for an easily assembled fiber laser system, which makes this design ideal for research laboratories aiming to develop compact and portable fs laser technologies that enable new implementations of clinical multiphoton microscopy and fs surgery.

A method is presented to build a custom low-cost, mode-locked femtosecond fiber laser for potential applications in multiphoton microscopy, endoscopy, and photomedicine. This laser is built using commercially available parts and basic splicing techniques.

用于多光子显微镜的全正常分散飞秒光纤激光器的低成本定制制造和模式锁定操作

A protocol is presented to build a custom low-cost yet high-performance femtosecond (fs) fiber laser. This all-normal-dispersion (ANDi) ytterbium-doped ...