Pulsed heterodyne Brillouin microscopy enables high-specificity, low-phototoxicity biomechanical imaging with single-ended access

TL;DR

Pulsed heterodyne Brillouin microscopy (PHBM) achieves high-resolution, low-phototoxicity biomechanical imaging with single-ended access, enabling detailed subcellular and tissue-level studies using significantly reduced optical power.

Contribution

This work introduces PHBM, a novel approach that reduces excitation energy by two orders of magnitude while maintaining high spectral resolution and precision in Brillouin microscopy.

Findings

Achieves 27 MHz spectral resolution with only 10 mW power.

Enables imaging of sensitive single cells and subcellular features.

Successfully images ex vivo porcine cornea with high quality.

Abstract

Brillouin microscopy (BM) enables three-dimensional, non-contact viscoelastic imaging with high spatial resolution. Since its introduction in 2008, different BM modalities have balanced accessibility and spectral performance. Spontaneous BM offers single-ended access but limited spectral resolution, while stimulated BM provides higher resolution but requires a dual-objective configuration, restricting sample types and thicknesses. Heterodyne BM combines single-ended access with high spectral resolution, yet its demand for high optical power (276 mW) and long pixel dwell time (100 ms) limits biological applications. Here, we present pulsed heterodyne Brillouin microscopy (PHBM), which reduces excitation energy by two orders of magnitude while maintaining high spectral resolution and precision. Using only 10 mW average power and 10 ms pixel dwell time, PHBM achieves 27 MHz intrinsic spectral resolution and 10 MHz shift precision in water. The low phototoxicity of PHBM enables imaging of sensitive single cells, revealing subcellular mechanical features. Moreover, we resolve double Brillouin peaks with frequency separations as small as 200 MHz, demonstrating high mechanical specificity. High-quality imaging of ex vivo porcine cornea further highlights the benefits of single-ended access for thick and complex tissues. The high-resolution, high-accuracy, calibration-free, alignment-free, compact and robust characteristics of PHBM opens new opportunities in biomedical research.