Fast acousto-optic tissue sensing with tandem nanosecond pulses experiments and theory

Photoacoustics allows imaging with optical contrast deep in biological tissues. The signal strength depends on the fluence distribution which is unknown. To obtain more quantitative photoacoustic measurements the signal must be normalized with acousto-optic measurements. In Acousto-optics light is modulated with ultrasound and the amount of modulated light detected is a measure for the fluence at the ultrasound focus. In this thesis a novel acousto-optic method is explored that can use the same laser system as the photoacoustics and overcomes one of the largest obstacles to apply acousto-optics in living tissues. This is achieved by reducing the signal acquisition time orders of magnitude compared with existing acousto-optic methods. This is done by recording the interference patterns from a coherent but short tandem laser pulse that consist of two pulses only tens of nanoseconds apart. This method enables acoustoptic measurements in biological tissues and fluency corrected photo acoustics.