Fig. 3: Optoacoustic sensing in liquids.

a Measured acoustic spectra with varying surrounding impedance Z. b Full width at half maximum of the TR21 mode versus acoustic impedance Z. c, d Spatial resolution characterization. c Surface plot of the acoustic spectrum at each scanning position z. d Measured impedance Z variation across the liquid interface. FWHM, Full width at half maximum. LSF, Line spread function.