Optically Tunable Bifunctional Structures Fabricated by Hybrid Imprint-Photo Lithography (HIPL)

Optically tunable bifunctional structures are created by hybrid imprint-photo lithography (HIPL), which is a combination of photolithography and soft lithography via a structured photomask. Prismatic patterns are formed on a flexible photomask, and the structured photomask is exploited as an imprint mold to create two-layered microstructures that show a tunable refraction property. Fabricated microstructures, such as the perpendicularly aligned cross-prismatic island (PAC-PI), show optically dual functionality that originates from each optical property of the upper and lower layers in two-layered structures with symmetric light collimation in the vertical and horizontal axes along both directions of the upper and lower prismatic layers, whereas a single conventional prismatic film shows only one-axis collimation. Moreover, tunability of the light collimation, which can be modulated by varying the area ratio of the upper and lower layers from 80% to 20% using optical simulation, is demonstrated. Such optically tunable bifunction on a single sheet could potentially reduce the number of required optical sheets, such as the liquid crystal display backlight unit (LCD BLU). This new hybrid lithography process could provide a potential pathway to construct highly complex optical components, such as planar waveguide, microlight emitting diode, virtual reality/augmented reality, and holographic display devices.