  In deep tissue photoacoustic imaging, the spatial resolution is inherently
limited by acoustic diffraction. Moreover, as the ultrasound attenuation
increases with frequency, resolution is often traded-off for penetration depth.
Here we report on super-resolution photoacoustic imaging by use of multiple
speckle illumination. Specifically, we show that the analysis of second-order
fluctuations of the photoacoustic images combined with image deconvolution
enables resolving optically absorbing structures beyond the acoustic
diffraction limit. A resolution increase of almost a factor 2 is demonstrated
experimentally. Our method introduces a new framework that could potentially
lead to deep tissue photoacoustic imaging with sub-acoustic resolution.
