Ultrafast measurement of photoacoustic parameters with mid-infrared frequency comb transients

초록

The photoacoustic (PA) effect has been widely used in various applications including highly sensitive spectroscopy and label-free non-invasive imaging. In this work we demonstrate a fast and precise measurement of PA parameters for light-absorbing liquids using mid-infrared asynchronous sampling pump-probe measurements. To simulate the observed PA oscillation signals and extract various PA parameters as a function of pump power we derived analytical solutions of the PA wave equation driven by a train of ultrashort Gaussian pump pulses. By fitting the analytical solution to the measured PA signals using a nonlinear curve fitting method we could measure the PA parameters including damping rate viscosity and natural frequency. Furthermore the dynamic response of thermophysical properties of the chloroform solution is also investigated by measuring the variation of the Grüneisen parameter with pump power. We anticipate that this work will open new possibilities for precise in situ measurements of the thermal properties of light-absorbing liquids. © 2024 Optica Publishing Group.