Fabrication of flexible metallic wire grid polarizer using thermal NIL and lift-off processes

Abstract

► Double layer metallic/dielectric gratings were fabricated for WGP components. ► Thermal NIL, aluminum lift-off, and dielectric etching were adopted in experiments. ► 192:1 Extinction ratio and 1.2× brightness gain were obtained with 240 nm pitch WGP. ► Designed optical performance and better process tolerance could be achieved. ► Low retardation COP films provide adequate optical performance. This work is dedicated to the fabrication of metallic/dielectric double layer gratings on polymeric films for wire grid polarizer (WGP) to obtain designed optical performance as well as better process tolerance. The fabrication process was based on thermal nanoimprint and aluminum lift-off techniques. Polymeric substrates PET (Polyethylene terephthalate) and COP (Cyclo-olefin polymer) were brought into comparison for the birefringence property. At the same time, by applying RCWA (Rigorous coupled-wave analysis) simulated optical designs, it would be also capable of minimizing difficulties of ultra-precision manufacturing. Experimental results revealed that using the 240 nm pitch stacked metallic/dielectric gratings performed 192:1 extinction ratio and 1.2× brightness enhancement, which allowed larger pitch replacing the smaller pitch of WGP gratings, but still possessed similar optical performance. Hence, these designs and process configuration not only make the continuous roll-to-roll process more feasible, but also relieve the difficulties of fabricating the imprint roller stamp.