Abstract

We demonstrate the effectiveness of stimulated Brillouin scattering for background-free Brillouin spectroscopy in scattering media within the biological spectral window. Using two nearly counter-propagating continuous-wave diode laser beams at 780 nm, we acquired transmission stimulated Brillouin point spectra in 10 mm and 500 μm thick Intralipid tissue phantoms with 100μm and 16μm diameter focal points, respectively. Stimulated gain spectra with high signal-to-noise ratio (8.7–30.7 dB) and frequency accuracy (6–72 MHz) were obtained at 20MHz/10ms and 20MHz/100ms through 0.24–3.36 mean-free paths of tissue phantoms. Our results suggest that stimulated Brillouin gain can be useful for imaging of Brillouin resonances in submillimeter-thick scattering samples.

© 2016 Optical Society of America

Quantitative measurements of material mechanics with spontaneous Brillouin scattering spectroscopy has gained much interest in recent years [14]. To produce the spontaneous Brillouin spectrum, a single laser beam at an angular frequency ω1 illuminates the sample. Light is then elastically and inelastically scattered from nonpropagating and propagating density fluctuations, respectively, to yield a spectrum that includes a single Rayleigh peak at ω1 and two Brillouin peaks with linewidth of ΓB at the acoustic Stokes and anti-Stokes resonances of the material. These Brillouin resonance frequencies are shifted from ω1 by the so-called Brillouin shift, ΩB, given for ΩBω1 by [5]

ΩB=(2ω1nvs/c)sin(θ/2).
Here, n and vs are the refractive index of and longitudinal speed of sound in the medium, respectively; c is the speed of light in air; and θ is the scattering angle with respect to the incident beam. The spontaneous Brillouin spectrum provides direct information on the viscoelastic properties of materials via the spectral shift ΩB and linewidth ΩB, which are in the GHz and 100s of MHz range for θ180°, respectively, [5]. In nonscattering matter, such as water, Brillouin shifts and linewidths have been measured using spectroscopy instruments that include Fabry–Perot interferometers [6,7], monochromators [8,9], and virtually imaged phased array (VIPA) spectrometers [1012]. However, in scattering materials, such as biological media, the strong elastic scattering background (i.e., Rayleigh peak) makes is difficult to effectively acquire Brillouin spectral data with these instruments due to the low signal-to-background ratio obtained.

Recently, extensions of VIPA spectrometers for spontaneous Brillouin scattering spectroscopy of scattering samples have been devised. One extension, proposed by Scarcelli and Yun, made use of multiple VIPA etalons cascaded in a cross-axis configuration to significantly suppress elastic scattering background [10], allowing in vivo imaging of the human eye [1]. Nevertheless, the throughput of multistage VIPA spectrometers decreases and their complexity increases with the number of VIPA stages. Another extension, reported by Meng et al., employed a heated iodine cell prior to the VIPA spectrometer to substantially filter out elastic scattering background [11], enabling probing of the mechanical properties of different tissue types [3]. However, application of molecular absorption cells as narrowband notch filters in spontaneous Brillouin spectroscopy setups requires the use of highly frequency stabilized lasers and algorithms that compensate for the distortion of measured Brillouin lines by the multiple absorption bands of the cell. Recently, Antonacci et al. have shown an interferometric method for significantly suppressing strong specular elastic reflections from planar interfaces in VIPA-based Brillouin spectroscopy [12]; yet, the question of how well this method performs in scattering samples remains to be investigated.

In this Letter, we show the utility of a different approach, based on stimulated Brillouin scattering (SBS) (de)amplification at 780 nm, for eliminating the elastic scattering background in transmission-mode Brillouin spectroscopy in thick and thin scattering tissue phantoms. To the best of our knowledge, although Brillouin spectroscopy using SBS (de)amplification was established a few decades ago, it was not applied to scattering, tissue-like, samples [1318]. Given the emerging importance of Brillouin spectroscopy in tissue [3,4], it is critical to study the effectiveness of SBS spectroscopy in tissue phantoms, particularly within the biological spectral window where light attenuation is governed by scattering rather than absorption. In SBS (de)amplification, the acoustic phonons are driven by interaction of the medium with two laser beams at angular frequencies ω1 (pump frequency) and ω2 (probe frequency) that intersect at an angle θ in the sample. When the frequency difference, Ω=ω1ω2, matches a particular Brillouin shift of the material ±ΩB, amplification (ω1>ω2) or deamplification (ω1<ω2) of the probe signal at ω2 occurs via stimulated Brillouin gain or loss (SBG/SBL) processes, respectively, [5,13]. Otherwise, when Ω does not match any acoustic resonance, no (de)amplification takes place. Consequently, unlike spontaneous Brillouin scattering, SBS (de)amplification does not exhibit elastic scattering background, thus, inherently providing excellent contrast, even in the presence of strong elastic scattering. Assuming a quasi-backscattering SBS process in scattering media (θ180°) and that changes in the pump power are governed by attenuation (due to scattering), SBG/SBL, defined as the steady-state small-signal stimulated fractional change in the probe power at ω2, G=ΔP2/P2L, is given by [19].

G(Ω)=ΔP2(Ω)/P2L=±ηg(Ω)LeffP10/A,
where P10(P2L) is the input power of the pump (probe) beam; Leff=[1exp(μtL)]/μt is the effective interaction length between the pump and probe beams in the medium; A is the area of the beams in the medium; and g represents the SBS gain factor which, to good approximation, is described by a Lorentzian with a spectral shift ΩB, linewidth ΩB and peak gain gpeak=g(ΩB) [5]. In addition, μt is the medium’s attenuation coefficient (which equals to the sum of absorption and scattering coefficients), and L is the medium’s length so that Ns=μtL describes the number of photon mean-free paths through the medium. Finally, η is the crossing efficiency defined as the overlap integral of the intensity of the Gaussian pump and probe beams crossed at an angle θ in the sample normalized by the overlap integral of two completely overlapping Gaussian beams crossed at θ=180° [15]. Note that Eq. (2) converges to the classical expression G=±gLP10/A for completely overlapping beams crossed at θ=180° in a nonattenuating medium (i.e., μt=0).

The SBS spectrometer arrangement is shown in Fig. 1(a). Unlike SBS spectroscopy systems that made use of solid-state and dye lasers as the pump light [1417], our setup employed two continuous-wave (CW) diode lasers as the pump and probe beams. Concretely, an amplified CW distributed feedback (DFB) laser and a second CW DFB laser (Toptica), both vertically polarized, thermally stabilized, and coupled into a polarization-maintaining single-mode fiber, were used as the pump and probe beams, respectively. Laser mode hop-free tuning ranges >50GHz and <4MHz laser linewidths were selected to offer wide spectral range and high spectral resolution. Note that the use of CW lasers avoids nonlinear sample photodamage induced by the high peak power of pulsed lasers. The pump and probe beams were focused into the sample, housed in a glass chamber, and were brought to coincide within the cuvette in a quasi-backscattering configuration for reducing stray pump light. Unless stated otherwise, pump and probe average powers of 270 and 15 mW were used on the sample, respectively. It is noteworthy that similar average power levels were employed in optical tweezers and showed no damage of living cells for <2min exposure times [20]. Unlike SBS spectroscopy systems reported in [17,18], we implemented a double-modulation lock-in detection scheme at radio frequencies (MHz range where diode lasers have low intensity noise) to measure the small SBG/SBL signals (106<G<105) with adequate signal-to-noise ratio (SNR). Explicitly, the intensity of the pump and probe beams was sinusoidally modulated at fm1=4MHz and fm2=5.1MHz, respectively, by acousto-optic modulators (Gooch & Housego, AA Opto-Electronic) and the resulting power modulation of the probe beam, conveying the SBG/SBL power signals, was detected at the difference frequency fm2fm1=1.1MHz with a large-area photodiode (Thorlabs) and a high-frequency lock-in amplifier (Stanford Research Systems) set to a specific time constant of τLIA=10, 100 ms, as depicted in Fig. 1(b).

 figure: Fig. 1.

Fig. 1. Transmission-mode SBS spectroscopy at 780 nm. (a) Experimental setup. C1/C2, fiber collimators; L1/L2, focusing lenses; AOM, acousto-optic modulator; L3L4/L5L6, relay lenses; MO, microscope objective; PD, large-area photodiode; FS, fiber splitter; FPD, fast photodetector; LIA, lock-in amplifier; FC, frequency counter, OSC, oscilloscope. (b) Spectrum diagram at PD output. RIN, relative intensity noise; dark red pump modulation power at fm1; light red probe modulation power at fm2; blue-red gradient, SBG/SBL modulation power at fm2fm1, which comprises the SBG/SBL signals in this Letter; red-blue gradient, SBG/SBL modulation power at fm2+fm1.

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To obtain stimulated spectra, we recorded SBG/SBL power signals as a function of the frequency detuning between the pump and probe lasers, Ω, with an oscilloscope (Tektronix). Ω was altered by scanning the frequency of the probe laser across the pump-laser frequency at a constant rate (dω2/2πdt=2, 0.2GHz/s) via linear ramp small modulation of the probe laser current. The frequency difference, Ω, was measured continuously by detecting the beat frequency between beams peeled from the main beams of the pump and probe lasers with a fast photodetector (New-Focus) followed by a frequency counter at a resolution of 10 MHz (Phase Matrix), as seen in Fig. 1(a). We first verified that the SBS spectrometer robustly produces spectra of nonscattering liquids. Figure 2(a) shows representative SBS spectra of methanol and dimethyl sulfoxide (DMSO). Dotted curves are the measured spectra, and solid curves are nonlinear least-squares fits of a pair of Lorentzians to the data. For these measurements, τLIA=100ms and dω2/2πdt=0.2GHz/s. In addition, the pump and probe beams, crossed at θ179°, were focused to 100μm diameter spots into a 10 mm thick glass chamber by 200 mm lenses, resulting in an estimated η28%.

 figure: Fig. 2.

Fig. 2. Transmission SBS spectra of (a) nonscattering liquids and (b) water and scattering Intralipid solutions. The cuvette photos show increased light attenuation with increasing Intralipid concentration in the solution (red, 0%; lightest gray, 0.019%; black, 0.103%). Note that a pump power of 95 mW was used on the methanol samples.

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From Fig. 2(a), we see that the Stokes-SBG and anti-Stokes-SBL peaks are evident in the spectra of methanol and DMSO while, unlike in spontaneous Brillouin spectra, the Rayleigh peak is eliminated. In addition, we observe that the fitted Lorentzian line shapes agree well with the measured spectra. Note that our SBS spectra of nonscattering liquids show comparable peak gain to that in [17], but that our SBS spectra were acquired at a 10–20 fold higher rate and without balanced detection. Using multiple fits to repeatedly measured stimulated spectra, estimates for the Brillouin shifts and linewidths of methanol (Ω^B/2π=3.799±0.006GHz and Γ^B/2π=187±7MHz) and DMSO (Ω^B/2π=5.655±0.016GHz and Γ^B/2π=547±23MHz) were obtained. These estimates are comparable to published Brillouin data [5,11,13].

Next, to show the effectiveness of our SBS spectrometer in scattering tissue phantoms at 780 nm with no elastic scattering background, we acquired stimulated spectra of Intralipid solutions at concentrations of 0.019%, 0.052%, and 0.103% in a 10 mm thick glass chamber. These concentration values correspond to media, where ballistic/quasi-ballistic light propagates with a number of mean-free paths of Ns=0.47, 1.33, and 2.61, respectively, evaluated by Beer–Lambert’s law [21]. Experimental conditions were the same as for DMSO in Fig. 2(a). The solid curves in Fig. 2(b) depict representative stimulated spectra from these solutions where the curve’s gray tone darkens with Intralipid concentration. For clarity, only fits to the measured spectra are shown. In addition, for comparison, we present the measured (blue dots) and fitted (red solid line) stimulated spectrum of water. The stimulated spectra of the Intralipid phantoms in Fig. 2(b) show excellent contrast and are similar to that of water in terms of Brillouin shifts and linewidths (Ω^B/2π=5.0875.102±0.0090.038GHz and Γ^B/2π=290296±1746MHz). Small stimulated Rayleigh peaks were infrequently observed in the Intralipid stimulated spectra, probably due to the nonzero absorption of Intralipid at 780 nm. Finally, Fig. 2(b) shows a reduction in the SBG/SBL peaks (and, hence, in SNR) with increasing scattering.

To quantify the dependence of the SBG signal’s SNR and precision of the Brillouin shift estimates on the degree of scattering and acquisition time, we measured the SNR of SBG power spectra of 0-0.119% Intralipid solutions in a 10 mm thick glass chamber under the same focusing and power conditions of Fig. 2(b). Spectra were acquired around their Stokes resonance over a 2 GHz bandwidth at τLIA=10, 100 ms and dω2/2πdt=2, 0.2GHz/s, respectively, resulting in a total acquisition time per spectrum of 1, 10 s, respectively. Note that heating by absorption of water can be neglected here as it was estimated to be <0.35K [22]. The SNR was evaluated as the ratio of the SBG peak power (at the Intralipid’s Brillouin shift) to the standard deviation of the noise skirt in the spectrum over a bandwidth of 1 GHz [17]. Figure 3(a) displays the mean (circles) and standard deviation (error bars) of the SNR estimated from 10 repeatedly measured spectra as a function of Ns=μtL and corresponding Intralipid concentration for τLIA=10ms (blue) and τLIA=100ms (red). For comparison, Fig. 3(a) also shows fits (solid lines) of the experimental SNR to the theoretical SNR given by

SNR=(RΔP2peakeμtL)2NEB+2qRP2LeμtLB+RIN(RP2LeμtL)2B.

 figure: Fig. 3.

Fig. 3. Measurements of (a) SBG signal’s SNR and (b) precision of the Brillouin shift estimates in scattering Intralipid solutions in a L=10-mm-thick glass chamber at τLIA=10ms (blue) and τLIA=100ms (red).

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The three terms in the denominator represent photodetector and lock-in amplifier electrical noise, shot noise, and RIN, respectively. Here, NE is the power spectral density of the photodetector and lock-in amplifier electrical noise, BτLIA1 is the effective detection bandwidth, q is the electron charge, R is the photodetector responsivity, RIN is the power spectral density of the probe laser RIN at fm2fm1, and ΔP2peak=G(ΩB)P2L is the SBG peak power [Eq. (2)]. Note that Eq. (3) becomes Eq. (4) in [17] for μt=0, NE=0 and negligible stray pump light. Fit parameters for Fig. 3(a) were G=4.23×106, R=0.55A/W, P10=270mW, P2L=15mW, A=π·502μm2, NE=0.014nA2/Hz, B=0.692Hz at τLIA=100ms, B=6.92Hz at τLIA=10ms, q=1.6×1019C, and RIN=137.9dB/Hz. Overall, we see from Fig. 3(a) that there is good agreement between the experimental and theoretical SNRs with a difference of 10dB in the SNR measured with τLIA=10, 100 ms, as predicted by Eq. (3). We can also observe that the dominant noise source depends on the value of Ns=μtL. In the current spectrometer, the RIN dominated for Ns<1.5 whereas, for Ns>2.5, the electrical noise became dominant, and the SNR degraded at a higher rate with increasing Ns (than that for Ns<1.5), as indicated by the RIN and electrical noise limited SNR curves (gray dashed lines) in Fig. 3(a). Note that the SNR could be improved to be RIN limited for Ns>1 by amplifying the SBG signal with a low-noise, 20 dB gain amplifier prior to lock-in demodulation. Figure 3(b) shows the accuracy, δΩ^B, in terms of standard deviation, in determining the Brillouin shifts from the SBG power spectra (circles) against Ns of the Intralipid phantoms at τLIA=10ms (blue) and τLIA=100ms (red). Dashed lines are drawn to guide the eye for the δΩ^B measurements. We see that the precision for the Brillouin shift estimates decreased with increasing Ns for both time constants (due to the lower SNR in the more scattering samples) and was lower for τLIA=10ms than for τLIA=100ms (due to decrease in SNR measured with a smaller time constant). Note that a lower precision for Ω^B yields a larger value of δΩ^B in Fig. 3(b). While the above results demonstrate the ability of the prototype spectrometer to effectively measure SBS spectra of Intralipid tissue phantoms of μt<3cm1 (as μt=Ns/L with Ns<3 and L=10mm), biological tissues have attenuation coefficients, μt, larger by one order of magnitude or more [23]. To validate our SBS spectrometer for stimulated spectra measurements, we repeated the measurements of Fig. 3 for μt=060cm1 and L=500μm, so that Ns was still 3. Figures 4(a) and 4(b) show, respectively, experimental SNR (circles are mean values and error bars are standard deviations) and Brillouin shift estimation accuracy, δΩ^B, of the SBG signal against Ns and Intralipid concentration alongside fits (solid lines) to the theoretical SNR [Eq. (3)] for τLIA=10ms (blue) and τLIA=100ms (red). Note that Intralipid concentrations are 20 fold higher for L=500μm than for L=10mm. Fit parameters were the same as in Fig. 3(a), with the exception of G=4.86×106, A=π·82μm2, NE=0.027nA2/Hz, and RIN=136.5dB/Hz. In addition, for these measurements, the pump and probe beams, crossed at θ176°, were focused to 16μm diameter spots into the 500 μm thick glass chamber by using 30 mm lenses. Note that heating by absorption of water can be neglected here as it was evaluated to be <0.53K [22]. The SNR and δΩ^B measured for the thin tissue phantoms showed a similar behavior to that observed for the thick phantoms, as evidenced by comparing Fig. 3 with Fig. 4. This similarity can be explained by noting that SBG/SBL [Eq. (2)] depends on the product of the medium’s length, L (as μt1=L/Ns), and the pump intensity, P10/A, with L and P10/A scaling quadratically and inversely quadratically with the focused pump waist, respectively, removing the dependence of SNR [Eq. (3)] on the beam focusing numerical aperture.

 figure: Fig. 4.

Fig. 4. Measurements of (a) SBG signal’s SNR and (b) precision of the Brillouin shift estimates in scattering Intralipid solutions in a L=500 - μm-thick glass chamber at τLIA=10ms (blue) and τLIA=100ms (red).

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In conclusion, we have demonstrated the usefulness of transmission-mode SBS spectroscopy based on diode lasers for background-free Brillouin spectroscopy in thick (L=10mm, μt<3cm1) and thin (L=500μm, μt60cm1) tissue phantoms of Ns<3 at 780 nm. The measurement precision and number of scattering events for photons in the phantoms can be further increased by using balanced detectors (to achieve shot-noise limited detection with >14dB improvement in SNR for Ns3) and a true backscattering geometry (to maximize the crossing efficiency of the pump and probe beams in the sample and obtain a 11dB improvement in SNR). In future work, we intend to use the SBS spectrometer for Brillouin imaging in submillimeter-thick scattering (rather than nonscattering [18]) samples.

Acknowledgment

Itay Remer is grateful to the Azrieli Foundation for the Ph.D. fellowship award.

REFERENCES

1. G. Scarcelli and S. H. Yun, Opt. Express 20, 9197 (2012). [CrossRef]  

2. K. J. Koski, P. Akhenblit, K. McKiernan, and J. L. Yarger, Nat. Mater. 12, 262 (2013). [CrossRef]  

3. Z. Meng and V. V. Yakovlev, Proc. SPIE 9303, 930342 (2015). [CrossRef]  

4. G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015). [CrossRef]  

5. R. W. Boyd, Nonlinear Optics (Academic, 1992).

6. J. R. Sandercock, RCA Rev. 36, 89 (1975).

7. K. J. Koski and J. L. Yarger, Appl. Phys. Lett. 87, 061903 (2005). [CrossRef]  

8. E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990). [CrossRef]  

9. P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005). [CrossRef]  

10. G. Scarcelli and S. H. Yun, Opt. Express 19, 10913 (2011). [CrossRef]  

11. Z. Meng, A. J. Traverso, and V. V. Yakovlev, Opt. Express 22, 5410 (2014). [CrossRef]  

12. G. Antonacci, G. Lepert, C. Paterson, and P. Török, Appl. Phys. Lett. 107, 061102 (2015). [CrossRef]  

13. M. Damzen, Stimulated Brillouin Scattering: Fundamentals and Applications (IOP, 2003).

14. M. Denariez and G. Bret, Phys. Rev. 171, 160 (1968). [CrossRef]  

15. C. Y. She, H. Moosmüller, and G. C. Herring, Appl. Phys. B 46, 283 (1988). [CrossRef]  

16. G. W. Faris, L. E. Jusinski, and A. P. Hickman, J. Opt. Soc. Am. B 10, 587 (1993). [CrossRef]  

17. W. T. Grubbs and R. A. MacPhail, Rev. Sci. Instrum. 65, 34 (1994). [CrossRef]  

18. C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015). [CrossRef]  

19. G. P. Agrawal, Nonlinear Fiber Optics, 3rd ed. (Academic, 2001).

20. Y. Liu, G. J. Sonek, M. W. Berns, and B. J. Tromberg, Biophys. J. 71, 2158 (1996). [CrossRef]  

21. L. V. Wang and H. Wu, Biomedical Optics: Principles and Imaging (Wiley, 2007).

22. A. Schonle and S. W. Hell, Opt. Lett. 23, 325 (1998). [CrossRef]  

23. W.-F. Cheong, S. A. Prahl, and A. J. Welch, IEEE J. Quantum Electron. 26, 2166 (1990). [CrossRef]  

References

  • View by:

  1. G. Scarcelli and S. H. Yun, Opt. Express 20, 9197 (2012).
    [Crossref]
  2. K. J. Koski, P. Akhenblit, K. McKiernan, and J. L. Yarger, Nat. Mater. 12, 262 (2013).
    [Crossref]
  3. Z. Meng and V. V. Yakovlev, Proc. SPIE 9303, 930342 (2015).
    [Crossref]
  4. G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
    [Crossref]
  5. R. W. Boyd, Nonlinear Optics (Academic, 1992).
  6. J. R. Sandercock, RCA Rev. 36, 89 (1975).
  7. K. J. Koski and J. L. Yarger, Appl. Phys. Lett. 87, 061903 (2005).
    [Crossref]
  8. E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
    [Crossref]
  9. P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005).
    [Crossref]
  10. G. Scarcelli and S. H. Yun, Opt. Express 19, 10913 (2011).
    [Crossref]
  11. Z. Meng, A. J. Traverso, and V. V. Yakovlev, Opt. Express 22, 5410 (2014).
    [Crossref]
  12. G. Antonacci, G. Lepert, C. Paterson, and P. Török, Appl. Phys. Lett. 107, 061102 (2015).
    [Crossref]
  13. M. Damzen, Stimulated Brillouin Scattering: Fundamentals and Applications (IOP, 2003).
  14. M. Denariez and G. Bret, Phys. Rev. 171, 160 (1968).
    [Crossref]
  15. C. Y. She, H. Moosmüller, and G. C. Herring, Appl. Phys. B 46, 283 (1988).
    [Crossref]
  16. G. W. Faris, L. E. Jusinski, and A. P. Hickman, J. Opt. Soc. Am. B 10, 587 (1993).
    [Crossref]
  17. W. T. Grubbs and R. A. MacPhail, Rev. Sci. Instrum. 65, 34 (1994).
    [Crossref]
  18. C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
    [Crossref]
  19. G. P. Agrawal, Nonlinear Fiber Optics, 3rd ed. (Academic, 2001).
  20. Y. Liu, G. J. Sonek, M. W. Berns, and B. J. Tromberg, Biophys. J. 71, 2158 (1996).
    [Crossref]
  21. L. V. Wang and H. Wu, Biomedical Optics: Principles and Imaging (Wiley, 2007).
  22. A. Schonle and S. W. Hell, Opt. Lett. 23, 325 (1998).
    [Crossref]
  23. W.-F. Cheong, S. A. Prahl, and A. J. Welch, IEEE J. Quantum Electron. 26, 2166 (1990).
    [Crossref]

2015 (4)

Z. Meng and V. V. Yakovlev, Proc. SPIE 9303, 930342 (2015).
[Crossref]

G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
[Crossref]

G. Antonacci, G. Lepert, C. Paterson, and P. Török, Appl. Phys. Lett. 107, 061102 (2015).
[Crossref]

C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
[Crossref]

2014 (1)

2013 (1)

K. J. Koski, P. Akhenblit, K. McKiernan, and J. L. Yarger, Nat. Mater. 12, 262 (2013).
[Crossref]

2012 (1)

2011 (1)

2005 (2)

P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005).
[Crossref]

K. J. Koski and J. L. Yarger, Appl. Phys. Lett. 87, 061903 (2005).
[Crossref]

1998 (1)

1996 (1)

Y. Liu, G. J. Sonek, M. W. Berns, and B. J. Tromberg, Biophys. J. 71, 2158 (1996).
[Crossref]

1994 (1)

W. T. Grubbs and R. A. MacPhail, Rev. Sci. Instrum. 65, 34 (1994).
[Crossref]

1993 (1)

1990 (2)

E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
[Crossref]

W.-F. Cheong, S. A. Prahl, and A. J. Welch, IEEE J. Quantum Electron. 26, 2166 (1990).
[Crossref]

1988 (1)

C. Y. She, H. Moosmüller, and G. C. Herring, Appl. Phys. B 46, 283 (1988).
[Crossref]

1975 (1)

J. R. Sandercock, RCA Rev. 36, 89 (1975).

1968 (1)

M. Denariez and G. Bret, Phys. Rev. 171, 160 (1968).
[Crossref]

Agrawal, G. P.

G. P. Agrawal, Nonlinear Fiber Optics, 3rd ed. (Academic, 2001).

Akhenblit, P.

K. J. Koski, P. Akhenblit, K. McKiernan, and J. L. Yarger, Nat. Mater. 12, 262 (2013).
[Crossref]

Antonacci, G.

G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
[Crossref]

G. Antonacci, G. Lepert, C. Paterson, and P. Török, Appl. Phys. Lett. 107, 061102 (2015).
[Crossref]

Ballmann, C. W.

C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
[Crossref]

Benassi, P.

P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005).
[Crossref]

Berns, M. W.

Y. Liu, G. J. Sonek, M. W. Berns, and B. J. Tromberg, Biophys. J. 71, 2158 (1996).
[Crossref]

Boyd, R. W.

R. W. Boyd, Nonlinear Optics (Academic, 1992).

Bret, G.

M. Denariez and G. Bret, Phys. Rev. 171, 160 (1968).
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Cheong, W.-F.

W.-F. Cheong, S. A. Prahl, and A. J. Welch, IEEE J. Quantum Electron. 26, 2166 (1990).
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Damzen, M.

M. Damzen, Stimulated Brillouin Scattering: Fundamentals and Applications (IOP, 2003).

Denariez, M.

M. Denariez and G. Bret, Phys. Rev. 171, 160 (1968).
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Di Fabrizio, E.

E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
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Eramo, R.

P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005).
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Faris, G. W.

Giugni, A.

P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005).
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W. T. Grubbs and R. A. MacPhail, Rev. Sci. Instrum. 65, 34 (1994).
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Hell, S. W.

Herring, G. C.

C. Y. She, H. Moosmüller, and G. C. Herring, Appl. Phys. B 46, 283 (1988).
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Hickman, A. P.

Jusinski, L. E.

Kondiboyina, A.

G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
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Koski, K. J.

K. J. Koski, P. Akhenblit, K. McKiernan, and J. L. Yarger, Nat. Mater. 12, 262 (2013).
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K. J. Koski and J. L. Yarger, Appl. Phys. Lett. 87, 061903 (2005).
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Krams, R.

G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
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Lepert, G.

G. Antonacci, G. Lepert, C. Paterson, and P. Török, Appl. Phys. Lett. 107, 061102 (2015).
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Y. Liu, G. J. Sonek, M. W. Berns, and B. J. Tromberg, Biophys. J. 71, 2158 (1996).
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MacPhail, R. A.

W. T. Grubbs and R. A. MacPhail, Rev. Sci. Instrum. 65, 34 (1994).
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Mazzacurati, V.

E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
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McKiernan, K.

K. J. Koski, P. Akhenblit, K. McKiernan, and J. L. Yarger, Nat. Mater. 12, 262 (2013).
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Mehta, V. V.

G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
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Meng, Z.

Z. Meng and V. V. Yakovlev, Proc. SPIE 9303, 930342 (2015).
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C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
[Crossref]

Z. Meng, A. J. Traverso, and V. V. Yakovlev, Opt. Express 22, 5410 (2014).
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C. Y. She, H. Moosmüller, and G. C. Herring, Appl. Phys. B 46, 283 (1988).
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P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005).
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E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
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Nucara, A.

E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
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G. Antonacci, G. Lepert, C. Paterson, and P. Török, Appl. Phys. Lett. 107, 061102 (2015).
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G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
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G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
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W.-F. Cheong, S. A. Prahl, and A. J. Welch, IEEE J. Quantum Electron. 26, 2166 (1990).
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E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
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P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005).
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J. R. Sandercock, RCA Rev. 36, 89 (1975).

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C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
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C. Y. She, H. Moosmüller, and G. C. Herring, Appl. Phys. B 46, 283 (1988).
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E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
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Silva, R. D.

G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
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Y. Liu, G. J. Sonek, M. W. Berns, and B. J. Tromberg, Biophys. J. 71, 2158 (1996).
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C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
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Török, P.

G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
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G. Antonacci, G. Lepert, C. Paterson, and P. Török, Appl. Phys. Lett. 107, 061102 (2015).
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Traverso, A. J.

C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
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Z. Meng, A. J. Traverso, and V. V. Yakovlev, Opt. Express 22, 5410 (2014).
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Y. Liu, G. J. Sonek, M. W. Berns, and B. J. Tromberg, Biophys. J. 71, 2158 (1996).
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Wang, L. V.

L. V. Wang and H. Wu, Biomedical Optics: Principles and Imaging (Wiley, 2007).

Welch, A. J.

W.-F. Cheong, S. A. Prahl, and A. J. Welch, IEEE J. Quantum Electron. 26, 2166 (1990).
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Wu, H.

L. V. Wang and H. Wu, Biomedical Optics: Principles and Imaging (Wiley, 2007).

Yakovlev, V. V.

C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
[Crossref]

Z. Meng and V. V. Yakovlev, Proc. SPIE 9303, 930342 (2015).
[Crossref]

Z. Meng, A. J. Traverso, and V. V. Yakovlev, Opt. Express 22, 5410 (2014).
[Crossref]

Yarger, J. L.

K. J. Koski, P. Akhenblit, K. McKiernan, and J. L. Yarger, Nat. Mater. 12, 262 (2013).
[Crossref]

K. J. Koski and J. L. Yarger, Appl. Phys. Lett. 87, 061903 (2005).
[Crossref]

Yun, S. H.

Appl. Phys. B (1)

C. Y. She, H. Moosmüller, and G. C. Herring, Appl. Phys. B 46, 283 (1988).
[Crossref]

Appl. Phys. Lett. (2)

G. Antonacci, G. Lepert, C. Paterson, and P. Török, Appl. Phys. Lett. 107, 061102 (2015).
[Crossref]

K. J. Koski and J. L. Yarger, Appl. Phys. Lett. 87, 061903 (2005).
[Crossref]

Biophys. J. (1)

Y. Liu, G. J. Sonek, M. W. Berns, and B. J. Tromberg, Biophys. J. 71, 2158 (1996).
[Crossref]

IEEE J. Quantum Electron. (1)

W.-F. Cheong, S. A. Prahl, and A. J. Welch, IEEE J. Quantum Electron. 26, 2166 (1990).
[Crossref]

J. Chem. Phys. (1)

E. Di Fabrizio, V. Mazzacurati, M. Nardone, A. Nucara, G. Ruocco, and G. Signorelli, J. Chem. Phys. 93, 7751 (1990).
[Crossref]

J. Opt. Soc. Am. B (1)

J. R. Soc. Interface (1)

G. Antonacci, R. M. Pedrigi, A. Kondiboyina, V. V. Mehta, R. D. Silva, C. Paterson, R. Krams, and P. Török, J. R. Soc. Interface 12, 20150843 (2015).
[Crossref]

Nat. Mater. (1)

K. J. Koski, P. Akhenblit, K. McKiernan, and J. L. Yarger, Nat. Mater. 12, 262 (2013).
[Crossref]

Opt. Express (3)

Opt. Lett. (1)

Phys. Rev. (1)

M. Denariez and G. Bret, Phys. Rev. 171, 160 (1968).
[Crossref]

Proc. SPIE (1)

Z. Meng and V. V. Yakovlev, Proc. SPIE 9303, 930342 (2015).
[Crossref]

RCA Rev. (1)

J. R. Sandercock, RCA Rev. 36, 89 (1975).

Rev. Sci. Instrum. (2)

P. Benassi, R. Eramo, A. Giugni, M. Nardone, and M. Sampoli, Rev. Sci. Instrum. 76, 013904 (2005).
[Crossref]

W. T. Grubbs and R. A. MacPhail, Rev. Sci. Instrum. 65, 34 (1994).
[Crossref]

Sci. Rep. (1)

C. W. Ballmann, J. V. Thompson, A. J. Traverso, Z. Meng, M. O. Scully, and V. V. Yakovlev, Sci. Rep. 5, 18139 (2015).
[Crossref]

Other (4)

G. P. Agrawal, Nonlinear Fiber Optics, 3rd ed. (Academic, 2001).

M. Damzen, Stimulated Brillouin Scattering: Fundamentals and Applications (IOP, 2003).

R. W. Boyd, Nonlinear Optics (Academic, 1992).

L. V. Wang and H. Wu, Biomedical Optics: Principles and Imaging (Wiley, 2007).

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Figures (4)

Fig. 1.
Fig. 1. Transmission-mode SBS spectroscopy at 780 nm. (a) Experimental setup. C 1 / C 2 , fiber collimators; L 1 / L 2 , focusing lenses; AOM, acousto-optic modulator; L 3 L 4 / L 5 L 6 , relay lenses; MO, microscope objective; PD, large-area photodiode; FS, fiber splitter; FPD, fast photodetector; LIA, lock-in amplifier; FC, frequency counter, OSC, oscilloscope. (b) Spectrum diagram at PD output. RIN, relative intensity noise; dark red pump modulation power at f m 1 ; light red probe modulation power at f m 2 ; blue-red gradient, SBG/SBL modulation power at f m 2 f m 1 , which comprises the SBG/SBL signals in this Letter; red-blue gradient, SBG/SBL modulation power at f m 2 + f m 1 .
Fig. 2.
Fig. 2. Transmission SBS spectra of (a) nonscattering liquids and (b) water and scattering Intralipid solutions. The cuvette photos show increased light attenuation with increasing Intralipid concentration in the solution (red, 0%; lightest gray, 0.019%; black, 0.103%). Note that a pump power of 95 mW was used on the methanol samples.
Fig. 3.
Fig. 3. Measurements of (a) SBG signal’s SNR and (b) precision of the Brillouin shift estimates in scattering Intralipid solutions in a L = 10 -mm-thick glass chamber at τ LIA = 10 ms (blue) and τ LIA = 100 ms (red).
Fig. 4.
Fig. 4. Measurements of (a) SBG signal’s SNR and (b) precision of the Brillouin shift estimates in scattering Intralipid solutions in a L = 500  -  μm -thick glass chamber at τ LIA = 10 ms (blue) and τ LIA = 100 ms (red).

Equations (3)

Equations on this page are rendered with MathJax. Learn more.

Ω B = ( 2 ω 1 n v s / c ) sin ( θ / 2 ) .
G ( Ω ) = Δ P 2 ( Ω ) / P 2 L = ± η g ( Ω ) L eff P 1 0 / A ,
SNR = ( R Δ P 2 peak e μ t L ) 2 N E B + 2 q R P 2 L e μ t L B + RIN ( R P 2 L e μ t L ) 2 B .

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