High spatiotemporal resolution optoacoustic sensing with photothermally induced acoustic vibrations in optical fibres

Optoacoustic vibrations in optical fibres have enabled spatially resolved sensing, but the weak electrostrictive force hinders their application. Here, we introduce photothermally induced acoustic vibrations (PTAVs) to realize high-performance fibre-based optoacoustic sensing. Strong acoustic vibrations with a wide range of axial wavenumbers k(z) are photothermally actuated by using a focused pulsed laser. The local transverse resonant frequency and loss coefficient can be optically measured by an intra-core acoustic sensor via spectral analysis. Spatially resolved sensing is further achieved by mechanically scanning the laser spot. The experimental results show that the PTAVs can be used to resolve the acoustic impedance of the surrounding fluid at a spatial resolution of approximately 10 mu m and a frame rate of 50Hz. As a result, PTAV-based optoacoustic sensing can provide label-free visualization of the diffusion dynamics in microfluidics at a higher spatiotemporal resolution. Optoacoustic sensing applications are limited by weak electrostrictive force. Here, the authors induce photothermally acoustic vibrations with a focused pulsed laser, and via scanning demonstrate sensing of acoustic impedance at 10 mu m spatial resolution, allowing for visualisation of diffusion dynamics.

Automated summary

In optoacoustic sensing, photothermally induced acoustic vibrations can achieve high-performance spatial resolution sensing through a focused pulsed laser, overcoming the limitation of weak electrostrictive force. Through optical measurement and mechanical scanning, high spatial resolution acoustic impedance resolution up to 10 micrometers can be achieved.