用于材料分析的高速连续波受激布里渊散射光谱仪
Summary
我们描述了一个快速 continuous-wave-受激-布里渊散射 (CW-SBS) 光谱仪的构造。该光谱仪采用单二极管激光器和原子蒸气缺口滤波器来获得高光谱分辨率的混浊/non-turbid 样品的透射光谱, 其速度比现有的 CW-SBS 光谱仪快100倍。这种改进可以实现高速布里渊材料分析。
Abstract
近年来, 自发布里渊光谱仪在非接触性分析软物质, 如水溶液和生物材料等方面的使用有了显著增加, 获得了快速的采集时间。在这里, 我们讨论的组装和运行的布里渊光谱仪, 使用受激布里渊散射 (SBS) 测量的受激布里渊增益 (SBG) 光谱的水和脂 emulsion-based 组织样样品在传输模式与 < 10 兆赫光谱分辨率和 < 35 MHz 布里渊位移测量精度在 < 100 ms. 分光计由两个近拉曼光 continuous-wave (CW) 窄线宽激光器组成, 其频率失谐的 780 nm 扫描通过材料布里渊移位。通过采用 ultra-narrowband 热 rubidium-85 气陷式过滤器和相敏探测器, 与现有的 CW-SBS 光谱仪相比, SBG 信号的信噪比得到显著提高。这种改进使测量的 SBG 频谱高达100倍的更快的采集时间, 从而促进高光谱分辨率和高精度的布里渊分析软材料的高速。
Introduction
自发布里渊光谱学近年来已经建立, 作为一种有价值的方法, 用于机械分析软材料, 如液体, 真实组织, 组织幻影和生物细胞1,2, 3,4,5,6,7。在这种方法中, 一个单一的激光照射的样品和光, 是弹性散射从自发的热声波在介质中收集的分光计, 提供有用的信息的粘弹性性质的样品。自发布里渊频谱包括两个布里渊峰在声波斯托克斯和反斯托克斯共振的材料, 和瑞利峰在照明激光频率 (由于弹性散射光)。对于布里渊散射几何, 布里渊频率由几个 GHz 从照明激光频率转移, 有数百兆赫的频谱宽度。
当扫描法布里-珀罗光谱仪已 systems-of-choice 获得自发布里渊光谱在软物质1,2, 最近的技术进步在几乎成像相阵列 (VIPA)光谱仪已启用显着更快 (秒) 布里渊测量与适当的频谱分辨率 (子 GHz)3,4,5,6,7。在本协议中, 我们提出了一个不同的, 高速, 高光谱分辨率, 精确的布里渊光谱仪的基础上检测 continuous-wave-受激-布里渊散射 (CW-SBS) 光从 non-turbid 和混浊样品在一个几乎反散射几何。
在 cw-SBS 光谱中, continuous-wave (cw) 泵和探针激光器, 在频率上略谐, 在样品中重叠以刺激声波。当泵与探头横梁的频率差与材料的特定声学共振相匹配时, 探头信号的放大或 deamplification 分别由受激布里渊增益或损耗 (SBG/SBL) 过程提供;否则, 没有 SBS (de) 放大发生8,9,10,11。因此, SBG (SBL) 频谱可以通过扫描在材料布里渊共振的激光之间的频率差和检测增加 (减少), 或增益 (损失), 在探针强度由于 SBS。与自发布里渊散射不同的是, 弹性散射背景在 SBS 中是固有的, 在混浊和 non-turbid 样品中都能得到优异的布里渊对比度, 而不需要 VIPA 的瑞利滤波器。光谱仪10,11,13。
CW-SBS 光谱仪的主要组成部分是泵浦和探针激光器以及受激布里渊增益/损耗检测器。对于高光谱分辨率, 高速 CW-SBS 光谱学, 激光器需要单 (#60; 10 MHz 线宽) 与足够宽波长调谐 (20-30 ghz) 和扫描率 (和 #62; 200 GHz/秒), 长期频率稳定 (和 #60; 50MHz/小时) 和低强度噪音。此外, 该泵 (探头) 横梁上需要具有几百 (数十) 兆瓦的功率的线性偏振和衍射有限激光束。最后, 应设计受激布里渊增益/损耗检测器, 以可靠地检测弱向后受激布里渊增益/损耗 (SBG/SBL) (10-5 -10-6) 的软物质。为了满足这些需求, 我们选择了分布式反馈 (DFB) 二极管激光器耦合到极化维护光纤和受激布里渊增益/损耗探测器结合 ultra-narrowband 原子蒸气缺口滤波器single-modulation 锁相放大器, 如图 1所示。此检测方案使 SBG 信号的强度加倍, 同时显著降低探头强度中的噪声, 而所需的 SBG 信号嵌入11。请注意, 在我们的 SBS 光谱仪中使用的原子气陷式过滤器的作用是显著减少不需要的杂散泵反射的检测, 而不是减少在 VIPA 光谱仪中检测到的弹性散射背景自发瑞利和布里渊散射光。使用下面详述的协议, 可以构造一个 CW-SBS 光谱仪, 能够获得水和组织幽灵的透射谱, 其 SBG 水平低至 10-6 , #60; 35 MHz 布里渊移位测量精度和在100毫秒以内。
图 1: 连续波受激布里渊散射 (CW-SBS) 光谱仪.两个 continuous-wave 泵和探针二极管激光器 (DL), 频率谐周围的布里渊转移的样本, 是耦合成极化维护单模光纤与直 c1和 c2, 分别。测量泵探头的频率差, 通过检测从泵剥离的光束和使用一组光纤分配器 (FS)、快速光电探测器 (平板显示器) 和频率计数器 (FC) 的探测激光器之间的跳动频率。S 极化探头光束 (浅红色), 扩展使用 Keplerian 光束膨胀器 (l1和 l2), 是右圆极化的四分之一波板 (λ1/4), 并专注于样本 (S) 由一个消色差透镜 (l3)。为有效的 SBS 相互作用和光隔离, 泵梁 (深红色), 扩大使用 Keplerian 扩束器 (l5和 l6), 是第一个 P 极化使用波板λ2/4), 然后通过极化传输光束分配器 (PBS), 并最终留下圆极化的四分之一波板 (λ2/4), 并专注于样品与无色透镜 (l4; 与 l3相同)。请注意, 泵和探头横梁几乎 counter-propagate 在样品中, 并使用 S 型偏振器 (p) 来防止 p 极化泵光束 (来自λ1/4) 进入探针激光器。对于锁定检测, 泵浦光束在fm 上正弦调制, 并带有声光调制器 (AOM)。SBG 信号, 表现为强度变化在频率fm (参见插页), 被解调用由大面积光电二极管 (PD) 检测后的锁定放大器。为了显著消除光电二极管中的杂散泵反射, 在泵浦波长周围使用窄带布拉格滤波器 (BF) 和原子陷波器 (85RB), 同时用遮光虹膜 (I)。数据通过连接到个人电脑 (PC) 的数据采集卡进行记录, 以进一步分析布里渊频谱。所有折叠镜 (m1-m6) 用于将光谱仪放在一个 18 “×24” 板上, 垂直安装在光学工作台上, 以方便水样样品的放置。请单击此处查看此图的较大版本.
Protocol
Representative Results
Discussion
该系统在图 1中所示, 设计为在 18 “x 24” 板上构建, 可以垂直安装在光学表上, 从而便于放置水样样品。因此, 重要的是要强烈收紧所有的光学和机械元件, 并确保泵和探头梁是共线和同心的各种元素之前, 照亮样品在离轴几何。
观察受激布里渊增益信号的困难可能是由于过多的杂散泵反射, 掩盖了水样样品的弱布里渊增益 (~ 10-6)。为了解决这些可能遇到的困?…
Divulgations
The authors have nothing to disclose.
Acknowledgements
IR 感谢列基金会的博士奖学金奖。
Materials
| Probe diode laser head and controller | Toptica Photonics | SYST DL-100-DFB | Quantity: 1 |
| Pump amplified diode laser and controller | Toptica Photonics | SYST TA-pro-DFB | Quantity: 1 |
| FC/APC fiber dock | Toptica Photonics | FiberDock | Quantity: 3 |
| High power single mode polarization maintaining FC/APC fiber patchcord | Toptica Photonics | OE-000796 | Quantity: 1 |
| FC/APC fiber collimation with adjustable collimation optics | Toptica Photonics | FiberOut | Quantity: 1 |
| FC/APC fiber fixed collimator | OZ Optics | HPUCO-33A-780-P-6.1-AS | Quantity: 1 |
| Single mode polarization maintaining fiber splitter 33:67 | OZ Optics | FOBS-12P-111-4/125-PPP-780-67/33-40-3A3A3A-3-1 | Quantity: 1 |
| Single mode polarization maintaining fiber splitter 50:50 | OZ Optics | FOBS-12P-111-4/125-PPP-780-50/50-40-3S3A3A-3-1 | Quantity: 1 |
| f=25 mm, Ø1/2" Achromatic Doublet, SM05-Threaded Mount, ARC: 650-1050 nm | Thorlabs | AC127-025-B-ML | Quantity: 1 |
| f=30 mm, Ø1" Achromatic Doublet, SM1-Threaded Mount, ARC: 650-1050 nm | Thorlabs | AC254-30-B-ML | Quantity: 2 |
| f=50 mm, Ø1" Achromatic Doublet, SM1-Threaded Mount, ARC: 650-1050 nm | Thorlabs | AC254-50-B-ML | Quantity: 1 |
| f=100 mm, Ø1" Achromatic Doublet, SM1-Threaded Mount, ARC: 650-1050 nm | Thorlabs | AC254-100-B-ML | Quantity: 1 |
| f=200 mm, Ø1" Achromatic Doublet, SM1-Threaded Mount, ARC: 650-1050 nm | Thorlabs | AC254-200-B-ML | Quantity: 1 |
| Ø1/2" Broadband Dielectric Mirror, 750-1100 nm | Thorlabs | BB05-E03 | Quantity: 4 |
| Ø1" Broadband Dielectric Mirror, 750-1100 nm | Thorlabs | BB1-E03 | Quantity: 2 |
| 1" Polarizing beamsplitter cube, 780 nm | Thorlabs | PBS25-780 | Quantity: 1 |
| Ø1" Linear polarizer with N-BK7 protective windows, 600-1100 nm | Thorlabs | LPNIRE100-B | Quantity: 1 |
| Shearing Interferometer with a 1-3 mm Beam Diameter Shear Plate | Thorlabs | SI035 | Quantity: 1 |
| 6-Axis Locking kinematic optic mount | Thorlabs | K6XS | Quantity: 4 |
| Compact five-axis platform | Thorlabs | PY005 | Quantity: 1 |
| Pedestal mounting adapter for 5-axis platform | Thorlabs | PY005A2 | Quantity: 1 |
| Polaris low drift Ø1/2" kinematic mirror mount, 3 adjusters | Thorlabs | POLARIS-K05 | Quantity: 4 |
| Lens mount for Ø1" optics | Thorlabs | LMR1 | Quantity: 5 |
| Adapter with external SM1 threads and Internal SM05 threads, 0.40" thick | Thorlabs | SM1A6T | Quantity: 1 |
| Rotation mount for Ø1" optics | Thorlabs | RSP1 | Quantity: 2 |
| 1" Kinematic prism mount | Thorlabs | KM100PM | Quantity: 1 |
| Graduated ring-activated SM1 iris diaphragm | Thorlabs | SM1D12C | Quantity: 1 |
| Post-mounted iris diaphragm, Ø12.0 mm max aperture | Thorlabs | ID12 | Quantity: 2 |
| 1/2" translation stage with standard micrometer | Thorlabs | MT1 | Quantity: 3 |
| Ø1" Pedestal pillar post, 8-32 taps, L = 1" | Thorlabs | RS1P8E | Quantity: 1 |
| Ø1" Pedestal pillar post, 8-32 taps, L = 1.5" | Thorlabs | RS1.5P8E | Quantity: 2 |
| Ø1" Pedestal pillar post, 8-32 taps, L = 2" | Thorlabs | RS2P8E | Quantity: 4 |
| Ø1" Pedestal pillar post, 8-32 taps, L = 2.5" | Thorlabs | RS2.5P8E | Quantity: 1 |
| Ø1" Pedestal pillar post, 8-32 taps, L = 3" | Thorlabs | RS3P8E | Quantity: 4 |
| Short clamping fork | Thorlabs | CF125 | Quantity: 12 |
| Mounting base | Thorlabs | BA1S | Quantity: 8 |
| Large V-Clamp with PM4 Clamping Arm, 2.5" Long, Imperial | Thorlabs | VC3C | Quantity: 1 |
| Ø1/2" Post holder, spring-loaded hex-locking thumbscrew, L = 1" | Thorlabs | PH1 | Quantity: 2 |
| Ø1/2" Post holder, spring-loaded hex-locking thumbscrew, L = 1.5" | Thorlabs | PH1.5 | Quantity: 2 |
| Ø1/2" Post holder, spring-loaded hex-locking thumbscrew, L = 2" | Thorlabs | PH2 | Quantity: 6 |
| Ø1/2" Optical post, SS, 8-32 setscrew, 1/4"-20 tap, L = 1" | Thorlabs | TR1 | Quantity: 2 |
| Ø1/2" Optical post, SS, 8-32 setscrew, 1/4"-20 tap, L = 1.5" | Thorlabs | TR1.5 | Quantity: 2 |
| Ø1/2" Optical post, SS, 8-32 setscrew, 1/4"-20 tap, L = 2" | Thorlabs | TR2 | Quantity: 6 |
| Aluminum breadboard 18" x 24" x 1/2", 1/4"-20 taps | Thorlabs | MB1824 | Quantity: 1 |
| 12" Vertical bracket for breadboards, 1/4"-20 holes, 1 piece | Thorlabs | VB01 | Quantity: 2 |
| Si photodiode, 40 ns Rise time, 400 – 1100 nm, 10 mm x 10 mm active area | Thorlabs | FDS1010 | Quantity: 1 |
| Waveplate, zero order, 1/4 wave 780nm | Tower Optics | Z-17.5-A-.250-B-780 | Quantity: 2 |
| Waveplate, zero order, 1/2 wave 780nm | Tower Optics | Z-17.5-A-.500-B-780 | Quantity: 1 |
| Fiber coupled ultra high speed photodetector | Newport | 1434 | Quantity: 1 |
| Gimbal optical miror mount | Newport | U100-G2H ULTIMA | Quantity: 3 |
| linear stage with 25 mm travel range | Newport | M-423 | Quantity: 1 |
| Lockable differential micrometer, 25 mm coarse, 0.2 mm fine,11 lb. load | Newport | DM-25L | Quantity: 1 |
| XYZ Motor linear stage | Applied Scientific Instrumentation | LS-50 | Quantity: 3 |
| Stage controller | Applied Scientific Instrumentation | MS-2000 | Quantity: 1 |
| Sample holder | Home made | Custom | Quantity: 1 |
| Rubidium 85 Fused Silica spectroscopy cell with flat AR-coated windows, 150 mm length, 25mm diameter | Photonics Technologies | SC-RB85-25×150-Q-AR | Quantity: 1 |
| Thermally conductive pad 300 mm x 300 mm | BERGQUIST | Q3AC 300MMX300MM SHEET | Quantity: 1 |
| Heat tape 0.15 mm x 2.5 mm x 5 m, 4.29 W/m | KANTHAL | 8908271 | Quantity: 1 |
| Polytetrafluoroethylene tape 1/2'' x 12 m | Teflon tape | R.G.D | Quantity: 1 |
| Reflecting Bragg grating bandpass filter | OptiGrate | SPC-780 | Quantity: 1 |
| High frequncy aousto optic modulator | Gooch and Housego | 15210 | Quantity: 1 |
| Aousto optic modulator RF driver, frequncy: 210 MHz | Gooch and Housego | MHP210-1ADS2-A1 | Quantity: 1 |
| High frequncy lock-in amplifier | Stanford Research Systems | SR844 | Quantity: 1 |
| Frequency counter | Phase Matrix | EIP 578B | Quantity: 1 |
| Arbitrary function Generator | Tektronix | AFG2021 | Quantity: 2 |
| Data acquisition (DAQ) module | National Instruments | NI USB-6212 BNC | Quantity: 1 |
| Data acquisition (DAQ) software | National Instruments | LabVIEW 2014 | Quantity: 1 |
| Regulated DC power supply dual 0-30V 5A | MEILI | MCH-305D-ii | Quantity: 1 |
| Thermocouple | MRC | TP-01 | Quantity: 1 |
| Thermometer | MRC | TM-5007 | Quantity: 1 |
| Coaxial low pass filter DC-1.9 MHz | Mini Circuits | BLP-1.9+ | Quantity: 1 |
| 20% lipid-emulsion | Sigma-Aldrich | I141-100ml | Quantity: 1 |
| 24×40 mm cover glass thick:3 # | Menzel Glaser | 150285 | Quantity: 1 |
| Computational software | MathWorks | MATLAB 2015a |
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