Method and apparatus for focusing a laser

摘要

A method for focusing an ultrashort pulse laser relative to a workpiece using the position of a plasma formed by a laser. A laser beam is focused to a focal point. The high peak intensity of the ultrashort pulse laser ionizes air at the focal region to form a plasma. The intensity of the plasma varies as its position relative to the workpiece varies. The intensity of the plasma formed by the focused laser beam is detected. The position of the focal point relative to the workpiece is adjusted responsive to the detected intensity of the plasma.