Triplex micron-resolution acoustic, photoacoustic, and optical transmission microscopy via photoacoustic radiometry.

We present a new sensing technique, termed photoacoustic radiometry (PAR), for mapping the optical attenuation properties of a sample. In PAR, laser pulses attenuated via transmission through the sample impinge on the ultrasound transducer and generate a photoacoustic (PA) signal within it. Spatial variation of the optical attenuation properties of the sample influences the amplitude of the PAR signal, providing image contrast. Performed simultaneously with pulse-echo ultrasound and PA imaging, this triplex imaging technique enables rapid characterization of samples with micrometer-resolution in a single scan. In this work, we demonstrate that the PAR technique can be easily integrated into existing PA microscopy systems, with applications in imaging biological samples and non-destructive evaluation of optically opaque materials such as silicon wafers.