高速的sub-GHz光谱仪激布里渊散射分析
Summary
在这里，我们提出了一个协议，以建立一个快速的布里渊光谱仪。级联几乎成像相控阵（VIPA）标准具实现了测量速度比传统扫描法布里 – 珀罗光谱仪快1000倍以上。这种改进提供了用于组织和生物材料在低功率水平的体内布里渊分析。
Abstract
该协议的目标是建立一个平行的高灭绝和高分辨率光学布里渊光谱仪。布里渊光谱是可以用来获得粘弹性材料属性直接读数的非接触测量方法。它已经在材料特性，结构的监测和环境传感的有用工具。在过去，布里渊光谱已经通常使用扫描法布里 – 珀罗标准具来执行频谱分析。这个过程需要高亮度功率和长采集时间，使得该技术不适合生物医学应用。最近推出的新型光谱仪通过采用两个东哲在交叉轴配置克服了这一难题。这一创新使具有内生物组织的安全界限亚秒采集时间和照明电源子千兆赫（GHz）的分辨率频谱分析。通过这种改进促进了多种新的应用程序立方米rrently正在探索在生物研究和临床应用。
Introduction
布里渊散射，首先由Leon布里渊1于1922年描述的，是光从在固体和来自液体或气体的热密度波动的热声模的非弹性散射。的散射光的谱移，通常在子GHz的范围，提供了有关该入射光和与样品中的声子之间的相互作用的信息。其结果是，它可以提供关于被检查材料的粘弹性能的有用信息。
在其自发版本，布里渊散射通常具有横截面在拉曼散射的顺序，产生了非常弱的信号。此外，布里渊频移的幅度比拉曼位移较小的订单。因此，弹性散射光（来自瑞利和米氏散射），杂散光，而反向反射在样本上都可以很容易地掩盖了布里渊光谱特征。故，布里渊光谱仪不仅需要实现的sub-GHz光谱分辨率也高光谱对比度或灭绝。
在传统的布里渊光谱仪这些要求是由扫描光栅单色器，光学打浆方法，以及最普遍地，多遍扫描法布里-珀罗干涉仪2满足。这些方法测量每个频谱分量顺序。这种方法导致了采集时间为单个布里渊频谱范围从几分钟到几个小时，这取决于仪器和在样品上。两阶段VIPA光谱仪，使用该协议建立，具有收集所有频谱分量的内不到一秒，同时提供足够的消光（> 60 dB为单位），以有效地抑制其它杂散信号2的能力。
VIPA的标准具的整合是本光谱仪的关键要素。一个VIPA是一个坚实的标准具有三个不同的C浮动区域：在所述前表面，一个窄抗反射涂层条允许光进入VIPA，而表面的其余部分设有一个高反射（HR）涂层;在后表面的部分反射涂层允许的光的一小部分（〜5％），以进行发送。当聚焦到稍微倾斜VIPA的狭窄的入口时，光束被反射到子组件与VIPA 2内固定的相位差。子组件之间的干扰达到渴望的高光谱色散。在交叉轴配置对两个东哲行依次介绍了正交方向3光谱色散。在正交方向上的光谱色散空间上分离从不需要的串扰，这使得有可能仅拾取布里渊信号的布里渊峰。 图1显示的是两级VIPA分光计的示意图。下面的光学元件中的箭头指示的度自由稀土元素，其中的平移阶段应侧重。
图1.纯设置。一种光纤开出布里渊散射进入分光光度计。一个柱面透镜C1（F = 200 MM）将光聚焦到第一VIPA（VIPA1）的入口。另一个圆柱透镜的C2（F = 200毫米）映射的光谱角色散成空间分离C2的焦平面。在该平面中，垂直掩模用于选择光谱的所需部分。类似的结构如下，倾斜90度。光束通过球面透镜S1（F = 200毫米）传递并聚焦到第二VIPA（VIPA2）的入口狭缝。甲球面透镜S2（F = 200毫米）产生在其焦平面，其中另一条水平掩模被放置在二维光谱上分离的图案。该HORizontal掩模成像到使用的消色差透镜对的EMCCD相机。 请点击此处查看该图的放大版本。
本科生与一些光学课程和基本取向的经验应该能够建立和使用两个阶段的光谱仪。分光计最近已证明是与各种标准的光学探针的3,4,5（例如，共焦显微镜，内窥镜，裂隙灯检眼镜）兼容。这里，光谱仪被连接到共聚焦显微镜。激光被整合90:10分束器后对准成标准研究倒置显微镜系统。来自样品的背散射光被耦合进单模光纤，使得共焦显微镜。
Protocol
Representative Results
Discussion
这种分光计的配置的一个关键的设计特点是，两个阶段可以独立地对准。当一个VIPA标准具滑出光路，分光计阶段的其余镜片形成1：1的成像系统，使来自每个阶段的频谱图案被成像到CCD照相机。因此，它是直接回到任一个阶段以提高其性能，而不会影响其他级的对准。该组中的协议建议的平移阶段和自由度遵循这一理念，保持独立优化光谱仪的两个阶段的能力。
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Divulgazioni
The authors have nothing to disclose.
Acknowledgements
This work was supported in part by the National Institutes of Health (P41-EB015903, R21EY023043, K25EB015885), National Science of Foundation (CBET-0853773) and Human Frontier Science Program (Young Investigator Grant).
Materials
| OPTICS: | |||
| VIPA (virtual image phase array) | LIGH MACHINERY | Quantity: 2 | |
| Bundle of Three 423 Linear Stages with SM-25 Micrometers | NEWPORT | 423-MIC | Quantity: 1 |
| SS Crossed-Roller Bearing Translation Stage, 0.5 in., 8-32, 1/4-20 | NEWPORT | 9066-X | Quantity: 1 |
| Vernier Micrometer, 13 mm Travel, 9 lb Load Capacity, 50.8 TPI | NEWPORT | SM-13 | Quantity: 1 |
| Adjustable Width Slit | NEWPORT | SV-0.5 | Quantity: 2 |
| Compact Dovetail Linear Stage, 0.20 in. Z Travel, 1.57×1.57×1.38 in. | NEWPORT | DS40-Z | Quantity: 2 |
| Slotted Base Plate, 25 or 40mm to 65mm Stage, 1.1 in. Range | NEWPORT | B-2B | Quantity: 2 |
| Ø1/2" Optical Post, 8-32 Setscrew, 1/4"-20 Tap, L = 2", 5 Pack | THORLABS | TR2-P5 | Quantity: 2 |
| Ø1/2" Post Holders, Spring-Loaded Hex-Locking Thumbscrews, L = 2", 5 Pack | THORLABS | PH2-P5 | Quantity: 1 |
| Ø1/2" Post Holders, Spring-Loaded Hex-Locking Thumbscrew, L = 3", 5 Pack | THORLABS | PH3-P5 | Quantity: 1 |
| Imperial Lens Mount For 2" Optics, 8-32 Tap | THORLABS | LMR2 | Quantity: 2 |
| f=200.0 mm, Ø2" Achromatic Doublet, ARC: 400-700 nm | THORLABS | AC254-200-A | Quantity: 2 |
| Kinematic Mount for up to 1.3" (33 mm) Tall Rectangular Optics, Right Handed | THORLABS | KM100C | Quantity: 2 |
| Fixed Cylindrical Lens Mount, Max Optic Height: 1.60" (40.6 mm) | THORLABS | CH1A | Quantity: 2 |
| f = 200.00 mm, H = 30.00 mm, L = 32.0 mm, N-BK7 Plano-Convex Cylindrical Lens, Antireflection Coating: 350-700 nm | THORLABS | L1653L1-A | Quantity: 2 |
| Right-Angle Post Clamp, Fixed 90° Adapter | THORLABS | RA90 | Quantity: 1 |
| Adapter with External C-Mount Threads and Internal SM1 Threads | THORLABS | SM1A9 | Quantity: 1 |
| Studded Pedestal Base Adapter, 1/4"-20 Thread | THORLABS | PB4 | Quantity: 2 |
| Spacer, 2" x 3", 1.000" Thick | THORLABS | Ba2S7 | Quantity: 2 |
| 543 nm, f=15.01 mm, NA=0.17 FC/APC Fiber Collimation Pkg. | THORLABS | F260APC-A | Quantity: 1 |
| SM1-Threaded Adapter for Ø11 mm collimators | THORLABS | Ad11F | Quantity: 1 |
| Translating Lens Mount for Ø1" Optics, 1 Retaining Ring Included | THORLABS | LM1XY | Quantity: 1 |
| Single Mode Patch Cable, 450 – 600 nm, FC/APC, 2 m Long | THORLABS | P3-460B-FC-2 | Quantity: 1 |
| 1:1 Matched Achr. Pair, f1=30 mm, f2=30 mm, BBAR 400-700 nm | THORLABS | MAP103030-A | Quantity: 1 |
| SM1 Lens Tube…length to adjust depend on CCD, we have 3.5 inches | THORLABS | SM1LXX | Quantity: 1 |
| Base Adapters for Ø1/2" Post Holders and Ø1" Posts | THORLABS | BE1 | Quantity: 8 |
| Clamping Forks for Ø1/2" Post Holders and Ø1" Posts | THORLABS | CF125 | Quantity: 8 |
| HW-KIT5 – 4-40 Cap Screw and Hardware Kit for Mini-Series | THORLABS | HW-KIT5 | Quantity: 1 |
| D20S – Standard Iris, Ø20.0 mm Max Aperture | THORLABS | D20S | Quantity: 2 |
| FOR ENCLOSURE | |||
| 25 mm Construction Rail, L = 21" | THORLABS | XE25L21 | Quantity: 6 |
| 1" Construction Cube with Three 1/4" (M6) Counterbored Holes | THORLABS | RM1G | Quantity: 8 |
| Right-Angle Bracket for 25 mm Rails | THORLABS | XE25A90 | Quantity: 12 |
| 25 mm Construction Rail, L = 15" | THORLABS | XE25L15 | Quantity: 4 |
| 25 mm Construction Rail, L = 9" | THORLABS | XE25L09 | Quantity: 8 |
| High Performance Black Masking Tape, 2" x 60 yds. (50 mm x 55 m) Roll | THORLABS | T743-2.0 | Quantity: 1 |
| Low-Profile T-Nut, 1/4"-20 Tapped Hole, Qty: 10 | THORLABS | XE25T3 | Quantity: 1 |
| 1/4"-20 Low-Profile Channel Screws (100 Screws/Box) | THORLABS | SH25LP38 | Quantity: 1 |
| 60" (W) x 3 yds. (L) x 0.005" (T) (1.5 m x 2.7 m x 0.12 mm) Blackout Fabric | THORLABS | BK5 | Quantity: 1 |
| CAMERA, LASER and MICROSCOPE | |||
| EMCCD camera | ANDOR | iXon Ultra 897 | Quantity: 1 |
| 400 mW single mode green laser | LASER QUANTUM | torus 532 | Quantity: 1 |
| Research Inverted System Microscope | OLYMPUS | IX71 | Quantity: 1 |
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