Pulsed stimulated Brillouin microscopy

Area of Science:

• Biophysics
• Optical Microscopy
• Materials Science

Background:

• Stimulated Brillouin scattering (SBS) is a nonlinear optical technique used for probing mechanical properties of biological samples.
• High optical intensities are typically required for SBS, posing challenges for biological applications due to potential photodamage.
• Achieving sufficient signal-to-noise ratio (SNR) is crucial for accurate measurements.

Purpose of the Study:

• To demonstrate that pulsed SBS can achieve a higher SNR than spontaneous Brillouin scattering (SpBS) at comparable average power levels.
• To develop and validate a novel pulsed SBS scheme suitable for biological sample analysis.
• To enable high-resolution mapping of mechanical properties in biological samples.

Main Methods:

• Implementation of a novel pulsed SBS scheme utilizing low duty cycle, nanosecond pulses for pump and probe beams.
• Measurement of SNR using water samples under varying integration times and average power levels.
• Acquisition of high-resolution maps of Brillouin frequency shift, linewidth, and gain amplitude from in vitro cell samples.

Main Results:

• A shot noise-limited SNR exceeding 1000 was achieved with average powers of 10 mW (2 ms integration) and 50 mW (200 µs integration) on water samples.
• High-resolution maps of mechanical properties (frequency shift, linewidth, gain amplitude) were obtained from cells in vitro with a spectral acquisition time of 20 ms.
• The study verified theoretical predictions regarding the enhanced SNR of pulsed SBS.

Conclusions:

• Pulsed stimulated Brillouin scattering significantly outperforms spontaneous Brillouin scattering in terms of SNR for biological imaging.
• The developed pulsed SBS technique is suitable for high-resolution, non-damaging mechanical characterization of biological samples.
• This advancement opens new avenues for quantitative mechanical probing in cell biology and related fields.