Background-free Brillouin spectroscopy in scattering media at 780 nm via stimulated Brillouin scattering

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 100 μm and 16 μm 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 20 MHz/10 ms and 20 MHz/100 ms 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.