Laser-generation of ultrasonic X-waves using axicon transducers

Photoacoustic and classical ultrasound imaging are both based upon ultrasonic waves but use different contrast mechanisms. For the development of a scanning acoustic microscope that uses both contrasts, an axicon transducer generating nondiffracting ultrasound, also called X-waves, by illumination with short laser pulses is investigated. Such a transducer provides simultaneously high depth of field and high lateral resolution. In this work, the spatial and temporal characteristics of the laser-generated X-waves are investigated using experiments and theoretical simulations. The experimental results reveal a characteristic spatial pulse width of 50 mu m and a focal depth that complies well with the theoretical predictions.