The PKLT  laser writing system use a raster scan strategy to pattern the photomasks.

The Optical head with the final lens moves at a constant speed in the X direction and the Acousto-Optic Deflector (AOD) deflects the laser along the Y-axis creating sweeps.

This is repeated until the end of the pattern in the X-axis, creating a scan strip along the X direction. After completing a scan strip the optical head retraces and the stage moves to the Y position for the next scan strip. This process is repeated until the entire pattern area has been covered. During the sweeps the laser beam is modulated according to the pattern data in an Acousto-Optic Modulator (AOM).