Aperture-induced spectral effects in stimulated Brillouin scattering microscopy

Stimulated Brillouin scattering (SBS) microscopy is emerging as a promising approach for mechanical imaging in biological settings. It is based on a spectroscopic backscattering SBS setup, but with scanning of the sample and using higher apertures of the excitation and collection optics for adequate spatial sampling. Here, we provide direct experimental measurements and theoretical predictions of the aperture-induced spectral effects of SBS microscopy in water-a key constituent of biological systems. It is shown that with increasing numerical aperture (NA), the Brillouin frequency shift and peak gain decrease, while the Brillouin linewidth broadens asymmetrically with the commencing of an extended tail in the low frequency region for NA >similar to 0.5. Further, significant distortions of the Brillouin spectral line shape are predicted for NAs close to 1, affecting the ability to retrieve spectral parameters of the Brillouin medium precisely and accurately.

Automated summary

Stimulated Brillouin scattering (SBS) microscopy is a promising method for mechanical imaging in biological settings. Experimental measurements and theoretical predictions show that increasing numerical aperture (NA) in SBS microscopy leads to a decrease in Brillouin frequency shift and peak gain, as well as broadening and distortion of the Brillouin linewidth. These effects can limit the precision and accuracy of spectral parameter retrieval in biological systems.