Name: resonance fluorescence of an ingaas quantum dot in a planar cavity using orthogonal excitation and detection
Uploaded: 2017-10-13T15:00:00.000+00:00
Duration: 12 min 57 s
Description: Watch this Scientific Journal Video about Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection at JoVE.com

作者想承认所罗门提供样品。这项工作得到了国家科学基金会 (DMR-1452840) 的支持。

警告: 请注意对齐时激光散射的可能危险。佩戴适当的安全护目镜保护。为了便于对齐过程, 需要红外查看器 (IR 查看器)。IR 敏感的荧光卡也有帮助, 但没有必要. 
 1. 样品制备 <ol> <li> 使用菱形抄写员在样品的顶部表面边缘进行微小的划痕。用两对平端镊子将样品放在划痕两侧。应用一个外旋转扭矩与镊子和样品将劈. 
	注意: 长划痕是不必要的促进裂解, 它可能会削减通过波导层使光耦合不可能。切割的脸是微妙的, 任何触摸它的表面可能会损害波导管的脸. </li>
	<li> 用导热银漆或银环氧树脂将劈裂试样贴在铜样品板上. 
	注: 切割面应与安装板的边缘齐平, 使励磁激光器能在不受干扰的情况下命中样品面. </li>
	<li> 在低温中安装铜板, 以便通过低温窗口可光学地访问切割面和样品表面. </li>
</ol> 2。共振励磁路径的对准 注意: 为了使耦合效率最大化到波导中, 入射励磁梁的剖面必须与假想的向后传播光束相匹配, 从而退出波导. 
<ol> <li> 将励磁激光束粗对齐到试样的切割面. 
	<ol> <li> 使用光纤耦合器 FC0 和镜像 M0 的自由度, 在安装励磁透镜之前, 将励磁光束定向到样品的切割面上. </li>
		<li> 将激发光束水平地与光学表相对, 并与样品的平面相对应. </li>
	</ol> </li> <li> 安装励磁目标和 #160; E obj <ol> 将非球面透镜 E <li> obj 置于平移式装载中, 具有三度平移自由度。将 e 的 obj 放在激光器上, 并设置高度 #160; e obj 与示例的中心相同. </li>
		<li> 沿励磁路径在样品后面设置一个白纸屏幕。使用 IR 查看器观察在纸上的一个亮点, 因为激光通过样品. </li>
		<li> 幻灯片和 #160; E obj 向样品缓慢地移动, 直到在纸上看到一个清晰的样品轮廓图。调整和 #160 的高度和横向位置; E obj 使剪影位于明亮点的中央. </li>
		<li> 保持滑动 E obj 向样品缓慢移动, 屏幕上的侧面影像图像会放大。同时, 调整 E obj (左/右) 的横向位置以补偿侧面影像图像的水平移动. 
		注意: 在 E obj 的缓慢移动过程中, 衍射条纹将开始出现在某个点上。这提供了一个新的参考, 把焦点点在表面层的样品. </li>
		<li> 保持滑动和 #160; E obj 慢慢地向样本。在 e obj 的每个位置, 向左/向右移动 e obj 会增加条纹间距, 直到只有一个可见的边缘在屏幕上查找条纹. 
		注意: 将有两组条纹, 一个在左边, 一个在样品表面的右边. </li>
		<li> 定位幻灯片 E obj Eobj 在最小化可见条纹数的位置. </li>
	</ol> </li> <li> 对齐望远镜镜头 E1 和 E2 <ol> <li> 将镜片 E1 和 E2 插入以激光束为中心的励磁路径。位置 E2 与 #160 分离; E obj 由它们的焦点长度之和。将 E1 和 E2 之间的分隔设置为其焦距的总和, 例如 、f 1 + f 2 = 150 mm 和 #160; </li> <li> 使用 IR 查看器观察纸张的侧面影像和衍射图案。调整 E1 的高度以中心的剪影在明亮的激光照明点的中心. </li>
		在调整 E1 的横向位置时, <li> 滑动 E2 朝向或远离 E1。安全 E1 和 E2 在两个边缘组要么消失, 要么在视图中显示最小的条纹数. 和 #160; </li> <li> 在 E1 前插入垂直方向的偏光器, 并将其集中在励磁光束上. #160; 注意: 有些偏振微楔角, 在这种情况下, 励磁梁将经历一个角偏差。使用 E1 和 E2 来补偿这种偏差. </li>
	</ol> </li> </ol> 3。光致发光采集路径的对准 注意: 在集合路径中生成的成像系统的性能主要取决于 L obj 的定位精度, 因为它的焦距很短 (f obj = 10mm, NA = 0.55)。在 L obj 的对齐过程中涉及两个常规步骤: 使用氖激光器进行粗对准, 以及使用 GaAs 的光源和大容量激子发射进行微调。这些对准步骤与样品在室温下进行. 
<ol> <li> 对齐上述带隙 (氖) 励磁路径和安装摄像头: <ol> <li> 一对以上带隙激光束 (氖) 成单模光纤. </li>
		<li> 通过镜像 M3 将光纤准直器的输出光束直接 FC1 到样品上. </li>
		<li> 倾斜 FC1 水平居中, 将样品上的激光点放在离切割边缘大约1毫米的地方。水平倾斜 M3, 将激光束的后反射移到入射光束的正上方或下方。重复此过程多次, 直到满足两个条件. </li>
		<li> 垂直倾斜 FC1 和 M3, 使氖光束与光学工作台相对水平, 并将其对准样品. </li>
		<li> 使用 IR 查看器在样品上定位谐振激光器和氖激光点。检查氖激光光斑的中心与谐振激光光斑的高度相同。如果没有, 使用 FC1 和 M3 匹配的横梁高度, 同时保持氖光束水平与表. </li>
		<li> 将 non-polarizing 光束分配器立方体 (90:10) NPBS 插入到氖路径中。中心的立方体在事件氖光束. </li>
		<li> 将分束器输出的两个光束定位到集合路径, 一个来自示例的反射, 另一个来自多维数据集内的内部反射. </li>
		<li> 将立方体旋转一个小角度 (〜5度), 这样两个光束可以在出口处很容易地分开。从样品表面反射的光可以用来作为对齐相机的粗略指南. 
		注意: 当多维数据集绕垂直轴旋转时, 内部反射光束的方向不会改变. </li>
		<li> 根据 "光学" 选项卡对多维数据集进行级别le 通过确保氖梁对应的内部反射在立方体内是在同一高度的传入光束. </li>
		<li> 将红外敏感相机放在背面反射的氖光束的路径中。使用管透镜 L 凸轮 , 焦距为 200 mm, 将样品图像聚焦到相机上. 
		注: 国产管系统用于对镜头 L 凸轮 进行内部显示, 如 图 1 所示, 它可防止照相机检测到杂散光室的光线. </li>
		<li> 设置一个 800 nm long-pass 过滤器, F1, 在 L 凸轮 过滤出氖光, 这允许观察 PL 从样品与照相机. </li>
	</ol> </li> <li> 安装和优化镜头的位置 L obj <ol> <li> 将非球面透镜和 #160; L obj 在平移式装载中, 具有三度的平移自由度。中心和 #160; L obj 在氖激光器上, 并将分离从样本设置为焦距, f obj = 10 mm. </li>
		<li> 设置透镜对 L1 和 L2 (f 1 = f 2 = 50 mm), 方法是使用 X Y 平移装入, 其中一侧固定, 另一侧在由千分尺控制的横向平面上移动. 
		注: 镜头 L2 进入安装的活动侧。L1 由透镜管持有, 并附着在固定的安装一侧。管系统提供了自由调整两个镜头之间的距离, 拧入/出透镜管持有 L1 沿光轴. </li>
		<li> 将两个镜片之间的距离设置为 100 mm, 通过调整千分尺来设置 L2 在安装中心的位置. </li>
		<li> 将 L1 和 L2 镜头组合插入到 NPBS 和低温之间的氖路径中。将 L1 和 L obj 之间的距离设置为 f obj + f 1 。中心 L1 和 L2 在事件氖的灯光下. </li>
		<li> 将光源和薄膜插入到集合路径中, 如 图 1 所示。将透镜 K4 和 L2 之间的距离设置为其焦距的总和. </li>
		<li> 通过调整光源的角度来 L2 照明光束的中心. </li>
		<li> 调整薄膜的角度, 使背部反射的光照在相机图像中可见, 氖激发引起的 PL 点. 
		注: 为了对准, 你可以关闭现场的膜片, 以找到中心的照明区域. </li>
		<li> 仅使用照明灯, 通过查看照相机在样品上找到表面缺陷或灰尘。通过横向移动 L2, 根据需要搜索样品的其他部分. </li>
		<li> 轻微点击 L obj 沿光轴进出, 使缺陷或尘埃的边缘最锋利. </li>
		<li> 将 L2 移回装载的中心. </li>
		<li> 查看相机上的氖激发 pl 点, 并将 L obj 水平移动, 使 pl 点从样本的已切割边缘 1-2 mm. 
		注: 对于小于 1 mm 的距离, 将通过目标 L obj 收集来自样品的切割边缘的激光散射。在离切割面太远的距离上, 励磁光束在到达量子数据量之前会经历衰减, 从而降低了最大的激发功率. </li>
		<li> 水平移动 L2, 直到样品的边缘在光照下显示在相机上. </li>
		<li> "渐变 L" obj 垂直移动以在试样的劈边上寻找明亮的激光光斑, 这是由于共振激发光束在试样的劈裂面上的散射引起的. </li>
		<li> 将氖激发的 PL 点放在试样的切割边缘上的明亮光斑上. </li>
	</ol> </li> <li> 对氖励磁路径的重新调整, 关于 L obj 的新位置. 
	注: 为了最大限度地扫描面积和最小化晕, 有必要重新励磁光学和励磁光束就位置的 L obj 。
	<ol> <li> 移除 L1 和 L2。将励磁梁居中并 #160; L obj , 同时确保光束位于样本的曲面法线方向. </li>
		<li> 中心 L2 在装载上。中心 L1 和 L2 在入射励磁梁上。设置 L1 和 #160 之间的距离; obj 为两个焦点长度的总和, 即 , f 1 + f obj . </li>
		<li> 重新定位 L 凸轮 这样, 它是集中在反射氖光束。重新定位相机, 使氖兴奋 PL (使用 long-pass 过滤器) 在图像上居中. </li>
		<li> 调整照明灯和薄膜的角度, 使光照在 L2 和氖励磁引起的 PL 点上居中. </li>
	</ol> </li> <li> 对齐镜像 M1 和 M2. 
	注: 通过光谱仪向后定向的激光将促进对准。
	<ol> <li> 从照相机的示例中监视氖激发 PL。将虹膜 (虹膜 A) 放在薄膜和 M1 之间的 PL 上. </li>
		<li> 中心透镜 L 规范 在反向光束上, 并将其一个焦距 f 规范 远离光谱仪的入口狭缝. </li>
		<li> 通过反射两个反射镜、M1 和 M2, 从光谱仪向样品发送反向光束. </li>
		<li> 在 M2 和 L 规范 之间设置另一个虹膜 (虹膜 B) 并将其置于反向光束的中心. </li>
		<li> 引导 M2 到中心的反向光束虹膜 a. 引导 M1 中心的 PL b. 重复此过程多次, 直到满足两个标准. </li>
		通过监视房间光线的零阶衍射, <li> 在 CCD 上定位分光计的入口狭缝 (30 #956; m 宽度) 的中心. </li>
		<li> 打开光谱仪的入口狭缝。通过使用 800 nm 长通滤波器, 可以在 CCD 上观察到氖激励下样品的 PL. </li>
		<li> 引导 M1 在分光计的入口狭缝和 CCD 的中间高度中心这个点, 并引导 M2 到虹膜的反向光束中心. 重复此过程几次, 直到满足两个标准. </li>
		<li> 镜头对 L3 和 L4 的对齐: 在 PL 集合路径中的位置 L3, 位于 f 2 + f 3 远离镜头 L2。将 L4 放置到集合路径中, 其焦点长度的总和与 L3 分开, f 3 + f 4 。在 CCD 上调整 L4 的侧位以使 PL 点居中. </li>
	</ol> </li> </ol> 4。PL 集合路径与谐振励磁路径的重叠 <ol> <li> 将样本冷却到 4.2 K。利用上述波段的激励, 使用光谱仪来确定润湿层的发射波长 (通常在 880 nm 左右). </li>
	<li> 在 L 凸轮前面设置一个 800 nm long-pass 过滤器 F1, 以阻止氖光。在照明灯的帮助下, L2 水平移动, 在相机上定位样品的边缘. </li>
	<li> 设置侧面激发波长与润湿层共振。在相机上的样品的边缘找到一个明亮的散射点. </li>
	通过调整 E1 的侧位, <li> 观察 #34、条纹图案和 #34;通过横向移动 E1 使条纹的强度最大化. 
	注: #34; 条纹和 #34; 润湿层发射, 这意味着激发光束被耦合到样品的波导中. </li>
	<li> 垂直调整 E1 以移动条纹, 使其与氖激发的 PL 点重叠. </li>
	<li> 记录润湿层 PL 的强度. 在一个方向调整 E2, 然后优化 E1 的位置; 再次记录 pl 的强度, 并与以前的值进行比较. </li>
	<li> 如果强度增加, 则重复 E2 在同一方向的调整。如果强度降低, 则反转 E2 的调整。重复此过程可找到 E1 和 E2 的最佳位置. </li>
</ol> 5。单量子点的共振激发 p 类 = "jove_content">> 注意: 有两种可能的方法来实现谐振激励的单个量子数: (1) 调谐的激光激发频率匹配特定的量子共振;或 (2) 扫描的激光频率跨越的共振能量的量子, 直到共振荧光从一个单一的量子探针观察. 
<ol> <li> 方法 (1)-目标激发: <ol> <li> 设置分光计, 以监视在上述带隙激励下的量子点集合的发射波长中心的一阶衍射。打开光谱仪的入口狭缝. </li>
		<li> 调整上述波段励磁的功率, 直到发光背景出现由于润湿层的连续尾的励磁状态。关闭入口狭缝到30和 #956; m. </li>
		<li> 侧移 L2 以找到合适的量子, 例如, 在视图中最亮的一个。记录光谱的波长和 #160; 和 #955; 用光谱仪测量的 量子数 . </li>
		<li> 调谐谐振激励激光器的波长与 #955 相同的值; 
		注意: 通常, 光谱仪可以从光学中提取共振激发激光器的微弱信号。如果没有, 将分裂的励磁光束定向到光谱仪中. </li>
		<li> 通过微调激励激光器的频率, 使 CCD 上的量子荧光和 #39 强度最大化. 
		注意: 对于某些量子, 需要少量的氖光才能使量子点共振激发 10 , 31 , 32 。所需的氖激光功率通常是如此 low-a 几百纳瓦-没有任何荧光造成的完全由这氖光束可以检测到的 CCD. </li>
		<li> 通过调整透镜 E1 的高度和横向位置以及透镜 E2 的轴向位置, 从而最大限度地提高了量子位的 PL 强度。联合优化透镜 E1 和 E2 的位置, 以最大限度地提高量子点的共振荧光强度. </li>
	</ol> </li> <li> 方法 (2)-光谱搜索: <ol> <li> 设置光谱仪, 以监测一阶衍射在发射波长中心的量子点合奏。打开光谱仪的入口狭缝. </li>
		<li> 调整激发激光器的频率, 使其跨越能量范围。一个共振兴奋的量子点将出现在 CCD 上, 作为一个斑点包围几个通风环。选择一个明亮的量子. </li>
		<li> 通过微调激发激光器的波长来最大化其 PL 强度. </li>
		<li> 通过调整 E1and 的高度和横向位置来最大化圆点的 PL 强度, E2 透镜的轴向位置。联合优化透镜 E1 和 E2 的位置, 以最大限度地提高量子点的共振荧光强度. </li>
	</ol>
	</li>
</ol>

<ol>
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作者没有什么可透露的。

该协议的关键步骤是: 模式匹配和对波导模式的激励光束对准;和正确的对准和集中的收集光学。这些步骤中最困难的部分是初始对准;优化已对齐的设置的耦合是相对简单的。重叠的集合和励磁区域是一个步骤, 是简单的能力, 图像的样品在相机上, 但是非常困难的, 没有这种能力。为了有高质量的成像, 正确的科勒照明是至关重要的。科勒照明的主题超出了本协议的范围, 但在显微镜下是一个众所周...

单量子发射器与荧光检测相结合的共振激励是一种长期的实验性挑战, 主要是由于无法光谱强激发散射的弱荧光判别。然而, 这一困难在过去十年中成功地克服了两种不同的方法: 基于偏振判别的暗场共焦激发1,2,3,4 ,5, 基于空间模式判别的正交励磁检测6,7,8,9,10,11, 12、13、14。这两种方法都表现出强烈的抑制激光散射的能力, 因此在各种实验中被广泛采用, 例如, 自旋光子纠缠的观测5,15, 16 ,演示的着装状态2,7,12,17,18,1920,22,23,24,25,26, 并对受限旋转的操作进行了3,27,28,29,30。这两种方法都不能普遍适用于各种情况;每个都限于某些特定的条件。暗场技术利用光子自由偏振度来抑制激光散射。这项技术有几个优点。例如, 没有对定义良好的波导模式的要求, 这将启用共聚焦的实现。共焦实现允许圆极化励磁和可能更紧的焦点的励磁束在量子发射器, 导致更高的激发强度。然而, 这种极化选择法限制了检测极化与励磁极化的正交性, 从而防止了荧光极化特性的完全表征。与之相比, 空间模式判别法利用励磁传播模式与检测光束之间的正交性, 来抑制激光散射4, 从而保持了检测极化的完全自由。这一技术的约束是在样品中的波导结构的必要性, 提供了一个与探测模式正交的励磁模式, 并限制励磁极化与光束的传播方向垂直.
在这里, 我们演示了一个协议, 建立一个 free-space-based 正交励磁检测设置的共振荧光实验。与在空间模式判别方面的开创性工作相比, 当光纤被用来将光耦合到空腔6时, 该协议在可用空间中提供了一个解决方案, 并且不需要动态组件来装载示例或纤维在低温。对励磁光束方向和检测路径的精细控制由低温外部的光学操纵, 而非球面单线态透镜则作为低温冷区内的聚焦目标。我们提供有代表性的图像的关键对准步骤的过程中实现共振激发和检测的荧光从一个单一的量子点。
本演示所用的样品是通过分子束外延 (外延) 生长的。铟量子点 (量子) 嵌入在由两个分布式布拉格反射器 (DBRs) 限定的 GaAs 间隔中, 如图 1中示例的放大视图所示。在 DBRs 之间的 GaAs 间隔作为波导, 其中的励磁束被限制在全内反射。DBRs 也充当 wavevectors 的 high-reflectivity 镜, 对样品平面来说几乎是正常的。这形成一个法布里-珀罗模式, 量子夫妇发出荧光。法布里-珀罗模式必须与量子的发射波长λ共振, 这要求 gaas 间隔是一个整数倍数的λ/n, 其中 n 是 gaas 折射指数。在这个演示中, GaAs 间隔的厚度被选择为 4λ/n, 大约是1µm, 以便在入射激发光束的衍射有限光斑尺寸附近。更窄的间隔将导致励磁光束的耦合效率降低到波导管模式。
实验设置如图 1所示。为了最大限度地提高耦合效率, 选择一个非球面单目标 Eobj , 数值孔径 NA = 0.5, 焦距为 8 mm, 将励磁光束聚焦在试样的劈裂面上。Keplerian 望远镜 (由透镜对 E1 和 E2 组成) 在励磁路径中的作用是两倍的: (1) 填充励磁目标 Eobj的孔径, 因此励磁光束被紧紧地聚焦在波导的更好模式匹配 (这种实现的准直光束直径是2.5 毫米), 和 (2) 提供三自由度, 以机动的焦点的励磁梁在切割面的样品。镜头 E1 安装在 X Y 平移安装上, 提供了两自由度, 可以自由地在切割试样面的平面上移动励磁点。镜头 E2 安装在旋转变焦外壳上, 提供了选择样品中焦点深度的自由。这三自由度允许我们在不需要样本本身运动的情况下, 优化单个量子数的共振激励。
在荧光收集路径, 类似的镜头配置 (Lobj, L1, 和 L2) 是用来允许检测的荧光从不同部分的样本。从样品的光线集中在两个管透镜之一的红外敏感相机 (l凸轮) 或入口狭缝光谱仪 (l规范)。L1 沿 z-axis 的运动调整图像的焦点, L2 的横向平移使图像在样品的平面上扫描。L1 和 L2 的焦距是相等的, 所以它们的放大倍数是统一的。这样做是为了最大限度的范围 L2 可以翻译之前, 晕发生。
为了便于对量子点的对准和定位, 基于科勒照明的国产照明灯被纳入到安装中, 如图 1所示。科勒照明的目的是为样品提供均匀的光照, 并确保我光照光源的法师在样本图像中不可见。照明灯和采集路径的镜头配置是精心设计的, 以分离样品和光源的共轭图像平面。集合路径中的每个镜头都是通过其焦距的总和与相邻的透镜隔开的。这可以确保无论在何处的样品图像是在焦点-例如在相机的传感器-光源图像是完全焦。同样, 在光源图像聚焦的地方--例如目标的后焦平面--样本图像是完全焦的。光源是一个商业发光二极管 (LED) 发射在 940 nm。光圈膜片使照明强度的调整, 和场膜片确定的视野要照亮。实现均匀光照的关键是将透镜 K4 和 L2 之间的距离设置为两个透镜焦距的总和, 并确保 Lobj的光圈不被光照所充填。在此协议中, 光照还用于优化 Lobj和示例之间的距离。
目标 Lobj和任一管透镜在相机或光谱仪上提供20x 的放大倍数。在 lobj和 l规范之间的透镜对 L3 和 L4 形成另一 Keplerian 望远镜, 它为光谱仪的电荷耦合器件 (CCD) 上的图像提供额外的4x 放大倍数。增加镜头 L3 和 L4 的结果, 总放大率为 80x, 这是必要的空间区分荧光从附近的量子. L3 和 L4 安装在翻转支架上, 以方便放大倍数的切换, 因为20x 放大倍数在示例上提供更大的视图字段。
为了使采集路径的视场与励磁光束通过波导的路径重叠, 量子点润湿层连续的发射是有帮助的。通过测量上述带隙激励下试样的发射光谱, 可以确定润湿层的发射波长。对于我们的样品, 润湿层放射发生在大约880毫微米在 4.2 K。通过将一个cw激光束在 880 nm 连接到样品的波导中, 你可以观察 PL 从润湿层形成的条纹图案, 在伴随的视频中显示。条纹揭示了被耦合到波导中的激发光的传播路径。这种条纹的存在结合了图像表面的能力, 使对齐直接。

<table><tbody><tr><td>Tunable external cavity diode laser</td><td>Toptica Photonics</td><td>DL-Pro</td><td></td></tr><tr><td>Closed-cycle cryostat</td><td>Montana Instruments</td><td>Cryostation</td><td></td></tr><tr><td>Spectrometer, 750 mm focal length</td><td>Princeton Instruments</td><td>SpectraPro 2750</td><td></td></tr><tr><td>Thermoelectrically cooled charge-coupled device</td><td>Princeton Instruments</td><td>Pixis 100BR-eXcelon</td><td></td></tr><tr><td>HeNe laser</td><td>JDSU</td><td>1125P</td><td></td></tr><tr><td>Infrared sensitive camera</td><td>Sony</td><td>NEX-5TL</td><td>IR blocking filter removed</td></tr><tr><td>Power meter and detector</td><td>Newport</td><td>1918-C, 918D-IR-OD3</td><td></td></tr><tr><td>Adjustable aspheric fiber collimator</td><td>Thorlabs</td><td>CFC-8X-A</td><td></td></tr><tr><td>Air-Spaced Doublet Collimator</td><td>Thorlabs</td><td>F810APC-842</td><td></td></tr><tr><td>Protected Silver Mirrors x 5</td><td>Thorlabs</td><td>PF10-03-P01</td><td></td></tr><tr><td>Flip mounts x 2</td><td>Thorlabs</td><td>FM90</td><td></td></tr><tr><td>Aspheric condenser lens, f = 20 mm; K1</td><td>Thorlabs</td><td>ACL2520-B</td><td></td></tr><tr><td>Best form spherical lens, f = 50 mm; E2, L1, L2, K2</td><td>Thorlabs</td><td>LBF254-050-B</td><td></td></tr><tr><td>Best form spherical lens, f = 100 mm; E1, L4, K3, K4</td><td>Thorlabs</td><td>LBF254-100-B</td><td></td></tr><tr><td>Best form spherical lens, f = 200 mm; Lspec, Lcam</td><td>Thorlabs</td><td>LBF254-200-B</td><td></td></tr><tr><td>Plano-convex lens, f = 400 mm; L3</td><td>Thorlabs</td><td>LA1172-B</td><td></td></tr><tr><td>Molded glass aspheric lens, f = 8 mm; Eobj</td><td>Thorlabs</td><td>C240TME-B</td><td></td></tr><tr><td>Precision asphere, f = 10 mm; Lobj</td><td>Thorlabs</td><td>AL1210-B</td><td></td></tr><tr><td>Longpass Filters, 800 nm, x2</td><td>Thorlabs</td><td>FEL0800</td><td></td></tr><tr><td>Non-polarizing beam splitter cube (NPBS)</td><td>Thorlabs</td><td>BS029</td><td></td></tr><tr><td>Pellicle beam splitter</td><td>Thorlabs</td><td>BP108</td><td></td></tr><tr><td>Polarizer</td><td>Thorlabs</td><td>LPNIRE100-B</td><td></td></tr><tr><td>Light emitting diode, 940 nm</td><td>Thorlabs</td><td>M940D2</td><td></td></tr></tbody></table>

resonance fluorescence of an ingaas quantum dot in a planar cavity using orthogonal excitation and detection

同时进行共振激发和荧光检测的能力对于量子点 (量子) 的量子光学测量是非常重要的。没有荧光检测的共振激励-例如差分传输测量-可以确定发射系统的某些特性, 但不允许基于发射的光子的应用或测量。例如, 光子相关性的测量、Mollow 三重的观察以及单光子源的实现都需要收集荧光。非相干激发与荧光检测-例如, 上面带隙励磁-可以被用来创造单一的光子源, 但由于激发环境的干扰, 减少了光子的不可。基于量子的单光子源将不得不共振激发, 以具有高光子不可, 同时收集光子将是必要的, 以利用它们。我们演示了一种方法, 共振激发一个单一的量子, 嵌入在一个平面腔通过耦合励磁梁从样品的切割面, 而收集的荧光沿样品的表面法线方向。通过将励磁光束与腔体的波导模式进行仔细匹配, 激发光可以耦合到腔内, 并与量子点相互作用。散射光子可以耦合到腔的法布里-珀罗模式, 并在表面正常方向上逃逸。该方法在检测极化时允许完全自由, 但励磁极化受励磁光束传播方向的限制。从润湿层的荧光提供了一个指南, 使收集路径对齐的励磁梁。激发和探测模式的正交性使得单个量子数的共振激励具有可忽略的激光散射背景。

图 1显示了完成单个量子点共振激发所需设备的一个特定实现。其他认识是可能的, 但关键的组分是: 励磁路对耦合波导;引导荧光探测器的采集路径;沿采集路径激发的共焦励磁路径;和照明路径, 使样品表面成像。
图 2显示了两个具有代表性的 RPLE 频谱。它们是从一个中性量子点 (<stro...

Watch this Scientific Journal Video about Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection at JoVE.com

Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection

单自组装量子点的共振激励可以用一种与荧光采集模式正交的激励模式来实现。我们演示了一个方法使用的波导和法布里-珀罗模式的一个平面微腔周围的量子点。该方法允许完全自由的检测极化。

用正交激励和检测方法研究平面腔内铟量子点的共振荧光

The ability to perform simultaneous resonant excitation and fluorescence detection is important for quantum optical measurements of quantum dots (QDs). ...

resonance-fluorescence-an-ingaas-quantum-dot-planar-cavity-using

Research

JoVE Journal

Engineering

9.1K 次观看.  West Virginia University. 单自组装量子点的共振激励可以用一种与荧光采集模式正交的激励模式来实现。我们演示了一个方法使用的波导和法布里-珀罗模式的一个平面微腔周围的量子点。该方法允许完全自由的检测极化。

视频: Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection

Compact Quantum Dots for Single-molecule Imaging

Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study.
Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7.
Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1-yS shell, further coated with a multidentate polymer ligand modified with short polyethylene glycol (PEG) chains (Figure 1). Compared with conventional CdSe nanocrystals, HgxCd1-xSe alloys offer greater quantum yields of fluorescence, fluorescence at red and near-infrared wavelengths for enhanced signal-to-noise in cells, and excitation at non-cytotoxic visible wavelengths. Multidentate polymer coatings bind to the nanocrystal surface in a closed and flat conformation to minimize hydrodynamic size, and PEG neutralizes the surface charge to minimize nonspecific binding to cells and biomolecules. The end result is a brightly fluorescent nanocrystal with emission between 550-800 nm and a total hydrodynamic size near 12 nm. This is in the same size range as many soluble globular proteins in cells, and substantially smaller than conventional PEGylated QDs (25-35 nm).

We describe the preparation of colloidal quantum dots with minimized hydrodynamic size for single-molecule fluorescence imaging. Compared to conventional quantum dots, these nanoparticles are similar in size to globular proteins and are optimized for single-molecule brightness, stability against photodegradation, and resistance to nonspecific binding to proteins and cells.

紧凑型量子点的单分子成像

Single-molecule imaging is an important tool for  understanding the mechanisms of biomolecular function and for visualizing the  spatial and temporal ...

科研

工程学

Rejection of Fluorescence Background in Resonance and Spontaneous Raman Microspectroscopy

Raman spectroscopy is often plagued by a strong fluorescent background, particularly for biological samples. If a sample is excited with a train of ultrafast pulses, a system that can temporally separate spectrally overlapping signals on a picosecond timescale can isolate promptly arriving Raman scattered light from late-arriving fluorescence light. Here we discuss the construction and operation of a complex nonlinear optical system that uses all-optical switching in the form of a low-power optical Kerr gate to isolate Raman and fluorescence signals. A single 808 nm laser with 2.4 W of average power and 80 MHz repetition rate is split, with approximately 200 mW of 808 nm light being converted to &lt; 5 mW of 404 nm light sent to the sample to excite Raman scattering. The remaining unconverted 808 nm light is then sent to a nonlinear medium where it acts as the pump for the all-optical shutter. The shutter opens and closes in 800 fs with a peak efficiency of approximately 5%. Using this system we are able to successfully separate Raman and fluorescence signals at an 80 MHz repetition rate using pulse energies and average powers that remain biologically safe. Because the system has no spare capacity in terms of optical power, we detail several design and alignment considerations that aid in maximizing the throughput of the system. We also discuss our protocol for obtaining the spatial and temporal overlap of the signal and pump beams within the Kerr medium, as well as a detailed protocol for spectral acquisition. Finally, we report a few representative results of Raman spectra obtained in the presence of strong fluorescence using our time-gating system.

We discuss the construction and operation of a complex nonlinear optical
system that uses ultrafast all-optical switching to isolate Raman from fluorescence
signals. Using this system we are able to successfully separate Raman and fluorescence
signals utilizing pulse energies and average powers that remain biologically safe.

波谱与自发拉曼显微荧光背景的抑制

Raman spectroscopy is often plagued by a strong fluorescent background, particularly for biological samples. If a sample is excited with a train of ...

生物工程

Synthesis and Operation of Fluorescent-core Microcavities for Refractometric Sensing

This paper discusses fluorescent core microcavity-based sensors that can operate in a microfluidic analysis setup. These structures are based on the formation of a fluorescent quantum-dot (QD) coating on the channel surface of a conventional microcapillary. Silicon QDs are especially attractive for this application, owing in part to their negligible toxicity compared to the II-VI and II-VI compound QDs, which are legislatively controlled substances in many countries. While the ensemble emission spectrum is broad and featureless, an Si-QD film on the channel wall of a capillary features a set of sharp, narrow peaks in the fluorescence spectrum, corresponding to the electromagnetic resonances for light trapped within the film. The peak wavelength of these resonances is sensitive to the external medium, thus permitting the device to function as a refractometric sensor in which the QDs never come into physical contact with the analyte. The experimental methods associated with the fabrication of the fluorescent-core microcapillaries are discussed in detail, as well as the analysis methods. Finally, a comparison is made between these structures and the more widely investigated liquid-core optical ring resonators, in terms of microfluidic sensing capabilities.

Fluorescent-core microcavity sensors employ a high-index quantum-dot coating in the channel of silica microcapillaries. Changes in the refractive index of fluids pumped into the capillary channel cause shifts in the microcavity fluorescence spectrum that can be used to analyze the channel medium.

折光传感荧光芯微腔的合成和操作

This paper discusses  fluorescent core microcavity-based sensors that can operate in a microfluidic  analysis setup. These structures are based on the ...

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and entanglement, to solve certain problems exponentially faster than with the best known algorithms on a classical computer. Gate-defined lateral quantum dots on GaAs/AlGaAs are one of many avenues explored for the implementation of a qubit. When properly fabricated, such a device is able to trap a small number of electrons in a certain region of space. The spin states of these electrons can then be used to implement the logical 0 and 1 of the quantum bit. Given the nanometer scale of these quantum dots, cleanroom facilities offering specialized equipment- such as scanning electron microscopes and e-beam evaporators- are required for their fabrication. Great care must be taken throughout the fabrication process to maintain cleanliness of the sample surface and to avoid damaging the fragile gates of the structure. This paper presents the detailed fabrication protocol of gate-defined lateral quantum dots from the wafer to a working device. Characterization methods and representative results are also briefly discussed. Although this paper concentrates on double quantum dots, the fabrication process remains the same for single or triple dots or even arrays of quantum dots. Moreover, the protocol can be adapted to fabricate lateral quantum dots on other substrates, such as Si/SiGe.

This paper presents a detailed fabrication protocol for gate-defined semiconductor lateral quantum dots on gallium arsenide heterostructures. These nanoscale devices are used to trap few electrons for use as quantum bits in quantum information processing or for other mesoscopic experiments such as coherent conductance measurements.

纳米加工门定义的GaAs / AlGaAs多量子点横向

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and ...

Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing

The application of femtosecond four-wave mixing to the study of fundamental properties of diluted magnetic semiconductors ((s,p)-d hybridization, spin-flip scattering) is described, using experiments on GaMnAs as a prototype III-Mn-V system.&#160; Spectrally-resolved and time-resolved experimental configurations are described, including the use of zero-background autocorrelation techniques for pulse optimization.&#160; The etching process used to prepare GaMnAs samples for four-wave mixing experiments is also highlighted.&#160; The high temporal resolution of this technique, afforded by the use of short (20 fsec) optical pulses, permits the rapid spin-flip scattering process in this system to be studied directly in the time domain, providing new insight into the strong exchange coupling responsible for carrier-mediated ferromagnetism.&#160; We also show that spectral resolution of the four-wave mixing signal allows one to extract clear signatures of (s,p)-d hybridization in this system, unlike linear spectroscopy techniques.&#160;&#160; This increased sensitivity is due to the nonlinearity of the technique, which suppresses defect-related contributions to the optical response. This method may be used to measure the time scale for coherence decay (tied to the fastest scattering processes) in a wide variety of semiconductor systems of interest for next generation electronics and optoelectronics.

The technique of femtosecond four-wave mixing is described, including spectrally-resolved and time-resolved configurations. We illustrate the utility of this technique for the investigation of crucial physical properties in the III-V diluted magnetic semiconductors, afforded by its nonlinearity and high temporal resolution.

The application of femtosecond four-wave mixing to the study of fundamental properties of diluted magnetic semiconductors ((s,p)-d hybridization, ...

Implementation of a Reference Interferometer for Nanodetection

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing its free spectral range (FSR), the module is put in parallel with a fiber taper-microcavity system and then calibrated through isolating and eliminating random shifts in the laser frequency (i.e. laser jitter noise). To realize the taper-microcavity junction and to maximize the optical power that is transferred to the resonator, a single-mode optical fiber waveguide is pulled. Solutions containing polystyrene nanobeads are then prepared and flown to the microcavity in order to demonstrate the system&#8217;s ability to sense binding to the surface of the microcavity. Data is post-processed via adaptive curve fitting, which allows for high-resolution measurements of the quality factor as well as the plotting of time-dependent parameters, such as resonant wavelength and split frequency shifts. By carefully inspecting steps in the time-domain response and shifting in the frequency-domain response, this instrument can quantify discrete binding events.

A reference interferometer technique, which is designed to remove undesirable laser jitter noise for nanodetection, is utilized for probing an ultra-high quality factor microcavity. Instructions for assembly, setup, and data acquisition are provided, alongside the measurement process for specifying the cavity quality factor.

一个参考干涉仪的Nanodetection实施

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing ...

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states are indeed the resources for implementing various protocols, ranging from enhanced metrology to quantum communication and computing. A variety of devices can be used to generate non-classical states, such as single emitters, light-matter interfaces or non-linear systems3. We focus here on the use of a continuous-wave optical parametric oscillator3,4. This system is based on a non-linear &#967;2 crystal inserted inside an optical cavity and it is now well-known as a very efficient source of non-classical light, such as single-mode or two-mode squeezed vacuum depending on the crystal phase matching. 
Squeezed vacuum is a Gaussian state as its quadrature distributions follow a Gaussian statistics. However, it has been shown that number of protocols require non-Gaussian states5. Generating directly such states is a difficult task and would require strong &#967;3 non-linearities. Another procedure, probabilistic but heralded, consists in using a measurement-induced non-linearity via a conditional preparation technique operated on Gaussian states. Here, we detail this generation protocol for two non-Gaussian states, the single-photon state and a superposition of coherent states, using two differently phase-matched parametric oscillators as primary resources. This technique enables achievement of a high fidelity with the targeted state and generation of the state in a well-controlled spatiotemporal mode.

We describe the reliable generation of non-Gaussian states of traveling optical fields, including single-photon states and coherent state superpositions, using a conditional preparation method operated on the non-classical light emitted by optical parametric oscillators. Type-I and type-II phase-matched oscillators are considered and common procedures, such as the required frequency filtering or the high-efficiency quantum state characterization by homodyning, are detailed.

光与连续波光学参量振荡器的量子态工程

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states ...

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we demonstrate an optical spectroscopy method that is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots (QDs) using a standard, easy-to-use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser line-width limited resolution with multi-channel photoluminescence detection. Such a scheme allows for considerable improvement of resolution over that of a common single-stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonon&#39;s energy difference allows one to separate and filter out the laser light exciting the quantum dot. An advantageous feature of this method is its straight forward integration into standard spectroscopy setups, which are accessible to most researchers.

The manuscript describes a method of phonon-assisted quasi-resonant fluorescence spectroscopy that incorporates both laser-limited resolution and photoluminescence (PL) spectroscopy. This method utilizes optical phonons to provide linewidth-limited resolution spectra of atom-like semiconductor structures in the energy domain. The method is also easily realized with a single spectrometer optical spectroscopy setup.

高分辨率声子辅助准共振荧光光谱仪

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we ...

Determination of the Excitation and Coupling Rates Between Light Emitters and Surface Plasmon Polaritons

We have developed a unique method to measure the excitation and coupling rates between the light emitters and surface plasmon polaritons (SPPs) arising from metallic periodic arrays without involving time-resolved techniques. We have formulated the rates by quantities that can be measured by simple optical measurements. The instrumentation based on angle- and polarization-resolved reflectivity and photoluminescence spectroscopy will be described in detail here. Our approach is intriguing due to its simplicity, which requires routine optics and several mechanical stages, and thus is highly affordable to most of the research laboratories.

This protocol describes the instrumentation for determining the excitation and coupling rates between light emitters and Bloch-like surface plasmon polaritons arising from periodic arrays.

光发射器与表面等离子体极化激元的激发和耦合速率的测定

We have developed a unique method to measure the excitation and coupling rates between the light emitters and surface plasmon polaritons (SPPs) arising ...

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing

We present a protocol for performing gas spectroscopy using infrared degenerated four-wave mixing (IR-DFWM), for the quantitative detection of gas species in the ppm-to-single-percent range. The main purpose of the method is the spatially resolved detection of low-concentration species, which have no transitions in the visible or near-IR spectral range that could be used for detection. IR-DFWM is a nonintrusive method, which is a great advantage in combustion research, as inserting a probe into a flame can change it drastically. The IR-DFWM is combined with upconversion detection. This detection scheme uses sum-frequency generation to move the IR-DFWM signal from the mid-IR to the near-IR region, to take advantage of the superior noise characteristics of silicon-based detectors. This process also rejects most of the thermal background radiation. The focus of the protocol presented here is on the proper alignment of the IR-DFWM optics and on how to align an intracavity upconversion detection system.

Here, we present a protocol to perform sensitive, spatially resolved gas spectroscopy in the mid-infrared region, using degenerate four-wave mixing combined with upconversion detection.

用于定量气体传感的红外退化四波融合与上转换检测

We present a protocol for performing gas spectroscopy using infrared degenerated four-wave mixing (IR-DFWM), for the quantitative detection of gas species ...