A gas
discharge laser crystallization apparatus and method for performing a transformation of a
crystal makeup or orientation in a film on a workpiece is disclosed, which may comprise a
master oscillator power
amplifier MOPA or power oscillator power
amplifier configured XeF
laser system producing a
laser output light
pulse beam at a high repetition rate and high power with a pulse to pulse
dose control; an optical
system producing an elongated thin pulsed working beam from the laser output light
pulse beam. The apparatus may further comprise the laser
system is configured as a POPA laser system and further comprising:
relay optics operative to direct a first output
laser light pulse beam from a first laser PO unit into a second laser PA unit; and, a timing and control module timing the creation of a gas
discharge in the first and second laser units within plus or minus 3 ns, to produce the a second laser output light pulse beam as an amplification of the first laser output light pulse beam. The system may comprise
divergence control in the oscillator laser unit.
Divergence control may comprise an unstable
resonator arrangement. The system may further comprise a beam pointing control mechanism intermediate the laser and the workpiece and a beam
position control mechanism intermediate the laser and the workpiece. Beam parameter
metrology may provide
active feedback control to the beam pointing mechanism and
active feedback control to the beam
position control mechanism.