The mechanical properties of biological systems, such as cells and organisms, play a major role in their function and development. However, conventional techniques for assessing these properties have limitations, including restricted probing depths and the need for physical contact with the sample. Recently, Brillouin microscopy has been developed for biomechanical imaging at the micrometer level with high sensitivity, and with no sample contact or external mechanical stimulus. Whereas most of the development efforts in Brillouin biomicroscopy have employed spontaneous Brillouin scattering as the imaging mechanism, stimulated Brillouin scattering (SBS) has been untapped.

In this presentation, I will introduce a new approach for high-sensitivity, noncontact, mechanical bioimaging based on stimulated Brillouin scattering (SBS). The method uses continuous-wave, single-frequency lasers and a high-frequency phase sensitive detection scheme to extract, with high mechanical specificity, the Brillouin frequency shift, linewidth and gain in semi-transparent, multicellular organisms. These parameters are closely related to the high-frequency complex longitudinal modulus of the mechanical constituent in the sampling volume within the organism. Our approach provides a new means for robust, all-optical biomechanical imaging at practical imaging times.