Apparatus include a transmissive optical substrate configured to receive a plurality of laser beams propagating along respective parallel beam axes at respective initial beam displacements with respect to an optical axis of the transmissive optical substrate, and configured to produce laser output beams having reduced displacements, wherein the transmissive optical substrate includes first and second surfaces with respective first and second curvatures defined to increase an output beam magnification and to nonlinearly increase an output beam displacement from the optical axis for a linearly increasing input beam displacement from the optical axis.