We describe the construction of a rapid continuous-wave-stimulated-Brillouin-scattering (CW-SBS) spectrometer. The spectrometer employs single-frequency diode-lasers and an atomic vapor notch-filter to acquire transmission spectra of turbid/non-turbid samples with high spectral-resolution at speeds up to 100-fold faster than those of existing CW-SBS spectrometers. This improvement enables high-speed Brillouin material analysis.
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Method Article
High-speed Continuous-wave Stimulated Brillouin Scattering Spectrometer for Material Analysis
In This Article
Summary
Abstract
Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as aqueous solutions and biomaterials, with fast acquisition times. Here, we discuss the assembly and operation of a Brillouin spectrometer that uses stimulated Brillouin scattering (SBS) to measure stimulated Brillouin gain (SBG) spectra of water and lipid emulsion-based tissue-like samples in transmission mode with <10 MHz spectral-resolution and <35 MHz Brillouin-shift measurement precision at <100 ms. The spectrometer consists of two nearly counter-propagating continuous-wave (CW) narrow-linewidth lasers at 780 nm whose frequency detuning is scanned through the material Brillouin shift. By using an ultra-narrowband hot rubidium-85 vapor notch filter and a phase-sensitive detector, the signal-to-noise-ratio of the SBG signal is significantly enhanced compared to that obtained with existing CW-SBS spectrometers. This improvement enables measurement of SBG spectra with up to 100-fold faster acquisition times, thereby facilitating high spectral-resolution and high-precision Brillouin analysis of soft materials at high speed.
Introduction
Spontaneous Brillouin spectroscopy has been established, in recent years, as a valuable approach for the mechanical analysis of soft materials, such as liquids, real tissue, tissue phantoms and biological cells1,2,3,4,5,6,7. In this approach, a single laser illuminates the sample and light that is inelastically scattered from spontaneous thermal acoustic waves in the medium is collected by a spectrometer, providing useful information on t....
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Protocol
Note: Unless stated otherwise, (i) connect all mounts to post holders and tighten the post bases with a clamping fork or mounting base to the optical table, and (ii) use output laser powers of 2 - 10 mW for all alignment procedures.
Note: Turn on all electrical/optoelectronic devices in the setup and allow 30 min of warmup time prior to use.
1. Prepare the Probe Beam Optical Path
- Mount and align the fiber collimator of the probe laser.
- Connect the input fiber of a 33:67 FC/APC polarization-maintaining fiber splitter (port T of FS1) to the fiber coupler of the pr....
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Results
Figures 2b and 3b display typical point SBG spectra of distilled water and lipid-emulsion tissue phantom samples (with 2.25 scattering events and an attenuation coefficient of 45 cm-1) measured within 10 ms and 100 ms, respectively. For comparison, we measured the SBG spectra in 10 s as shown in Figures 2a and 3a. In these measurements, the rubidium-85 vapor cell was heated to 90 °C for attenuating stray pump r.......
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Discussion
The system, shown in Figure 1, was designed to be built on an 18'' x 24'' breadboard that can be mounted vertically on an optical table, facilitating placement of watery samples. As a result, it is important to strongly tighten all optical and mechanical elements and ensure that the pump and probe beams are collinear and concentric with the various elements prior to illuminating the sample in off-axis geometry.
Difficulties in observing the stimulated Brillouin.......
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Disclosures
The authors have nothing to disclose.
Acknowledgements
IR is grateful to the Azrieli Foundation for the PhD fellowship award.
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| 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-RB85-25x150-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 |
| round 25 mm diameter cover glass thick:1 # | Menzel Glaser | 150285 | Quantity: 1 |
| Computational software | MathWorks | MATLAB 2015a |
References
- Koski, K. J., Akhenblit, P., McKiernan, K., Yarger, J. L. Non-invasive determination of the complete elastic moduli of spider silks. Nat. Mater. 12 (3), 262-267 (2013).
- Palombo, F., Madami, M., Stone, N., Fioretto, D. Mechanical mapping with chemical specificity b....
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