Deliverable D5.1 - Beam shaping module

This deliverable gives an overview of the design, production and texturing performance of a beam shaping module designed to enable laser patterning of a SiO2 etch mask layer with a pitch of 3µm, demonstrating the industrial feasibility of laser texturing approaches as a step in the production of inverted pyramid textured surfaces having a the same pitch. Informed by expertise from ISFH & MBE, a spot size of 2 µm was defined as sufficiently small to allow for proper pyramid etching. A high NA (Na=0.27) focuser objective with a 2 mm field size was designed and simulated and found to achieve the desired spot size over the entire field. Three different beam splitting schemes were considered: a straightforward splitting of the laser light into a line of spots with 3 µm pitch, and two staggered approaches where the spot had the same 3 µm pitch in the line axis with shifts in the scanning direction in a zig zag or diagonal pattern. This was found in simulations to improve spot-spot uniformity by eliminating interference between neighbouring spots. Accordingly, 3 different DOE phase profiles were designed, one for each beam splitting scheme. Following review and approval by ISFH, Holo/Or produced the focusing objective (2 units) and provided the beam shaping modules (objective + integrated DOE, with DOEs being easily switchable) to ISFH.