Scattering cross-sectional modulation in photoacoustic remote sensing microscopy.

Area of Science:

• Optics and Photonics
• Acoustic Physics
• Materials Science

Background:

• Photoacoustic remote sensing microscopy utilizes laser-induced thermo-elastic expansion.
• Understanding scattering cross-section modulations is crucial for this technique.

Purpose of the Study:

• To model and observe scattering cross-sectional modulations in absorbing optical scatterers under pulsed laser excitation.
• To investigate the underlying thermo-elastic expansion mechanism and its impact on optical properties.

Main Methods:

• Development of a time-evolution model for laser-induced thermo-elastic expansion.
• Comparison of the model with existing theoretical models and experimental data.
• Observation and measurement of scattering cross-sectional modulations and acoustic enlargement effects.

Main Results:

• Predicted and observed fractional scattering cross-sectional modulations exceeding 20 times that of unperturbed particles.
• First-time observation of a nonlinear acoustic enlargement effect.
• Demonstration of significant perturbations to local refractive indices due to rapid expansion.

Conclusions:

• The developed model accurately captures the dynamics of laser-induced scattering changes.
• The findings advance the understanding and application of photoacoustic remote sensing microscopy.
• System and material properties significantly influence the observed photoacoustic phenomena.