A system for sub-surface photoalteration of a material comprising a laserconfigured toproduce a pulsed laser beam having a first pulse energy and a first focalpointseparation, a controller coupled to the laser and a scanner coupled to thecontroller.The controller is configured to determine the first pulse energy and the firstfocal pointseparation based on a relationship of pulse energy and focal point separationcombinations enabling layer separation of the material by photoalteration. Thecontrolleris further configured to select a focal point depth using the first pulseenergy and the firstfocal point separation based on a relationship of minimum focal point depthand acombination of minimum pulse energy and focal point separation. The scanner isconfigured to position the pulsed laser beam at the focal point depth selectedby thecontroller.
