Brillouin spectroscopy is a noncontact technique for characterizing the mechanical properties of materials. Typically, Brillouin spectrometers have been realized using scanning Fabry–Perot spectrometers that measure, with long acquisition times, spontaneous Brillouin scattering from the samples. In the last few years, the use of virtually imaged phase array (VIPA) etalons for constructing Brillouin spectrometers has enabled to acquire spontaneous Brillouin spectra <1,000-fold faster than with scanning Fabry–Perot spectrometers, opening up new means for high-speed Brillouin analysis of materials.
In this talk, we will present a different approach for high-speed Brillouin material analysis. The method uses continuous-wave stimulated Brillouin scattering (CW-SBS) to measure stimulated Brillouin gain (SBG) spectra of materials at <100 milliseconds – up to 100-fold faster than with existing CW-SBS spectrometers. The SBS spectrometer comprises two nearly counter-propagating single-frequency lasers at 780 nm whose frequency detuning is scanned through the material Brillouin shift. SBG is detected via an ultra-narrowband hot rubidium-85 vapor notch filter and a lock-in detector, resulting in an improved signal-to-noise ratio that enables to significantly shorten acquisition times. We will show that this improvement, combined with micrometer-step-size spatial scanning of the sample, provides precise Brillouin profiles of layered liquids at 30-milliseconds pixel-dwell-time, facilitating Brillouin profilometry analysis of materials at high speed.
Itay Remer and Alberto Bilenca, "High-speed Brillouin imaging via continuous-wave stimulated Brillouin scattering (Conference Presentation)," Proc. SPIE 10067, Optical Elastography and Tissue Biomechanics IV, 100670H (Presented at SPIE BiOS: January 29, 2017; Published: 24 April 2017); https://doi.org/10.1117/12.2251967.5380018827001.
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