title: Photoacoustic generation of focused quasi-unipolar pressure pulses.
abstract: The photoacoustic effect was employed to generate short-duration quasi-unipolar acoustic pressure pulses in both planar and spherically focused geometries. In the focal region, the temporal profile of a pressure pulse can be approximated by the first derivative of the temporal profile near the front transducer surface, with a time averaged value equal to zero. This approximation agreed with experimental results acquired from photoacoustic transducers with both rigid and free boundaries. For a free boundary, the acoustic pressure in the focal region is equal to the sum of a positive pressure that follows the spatial profile of the optical energy deposition in the medium and a negative pressure that follows the temporal profile of the laser pulse.
authors.affiliation: Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Maslov
authors.forename: Hao F
authors.initials: HF
authors.lastname: Zhang
authors.forename: Lihong V
authors.initials: LV
authors.lastname: Wang