Photomechanical effect
Lasers in medicine

When a very short laser pulse (nanoseconds and below) is focused on a tissue target, creating high irradiances (of the order of 10¹⁰ to 10¹² W/cm²), it is possible to locally obtain high electric fields (10⁶ to 10⁷ 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 effect is used in ophthalmology to destroy eye membranes.

The femtosecond laser operating on this principle is now used instead of ultrasound for fragmentation of the opacified lens nucleus...