3. Photomechanical effect

When a very short laser pulse (nanoseconds and below) is focused on a tissue target, creating high irradiances (of the order of 10 ¹⁰ to 10 ¹² W/cm ² ), it is possible to locally obtain high electric fields (10 ⁶ to 10 ⁷ V/m) comparable to atomic or intramolecular fields. Such fields induce electrical breakdown of the target material resulting in the formation of a plasma. The shockwave associated with plasma expansion generates extremely high pressure waves and consequently mechanical disruption of the tissue structure. This photomechanical effect is generally obtained with Nd:YAG lasers operating in triggered (ns) or phase-locked (ps) modes. In medicine, this...