Fabrication of long hexagonal micro-lens array by applying gray-scale lithography in micro-replication process

A hexagonal micro-lens (HML) array with long aspect ratio of 3.3:1 designed for beam shaping was fabricated by applying gray-scale lithography in micro-replication process. The gray-scale lithography process was employed in this study to obtain unity curvature and to maximize filling factor of the lens array. Precision micro-replication process was applied to duplicate HML on a flexible polyethylene terphthalate (PET) substrate by UV-forming process. The geometry character of obtained HML was inspected and the shape of HML is very close to the designed specification. The optical performance was also investigated. It was found that the incident Gauss beam was diversified differently at short and long axis. The beam full widths at the half maximum (FWHM) at short axis and long axis directions through the HML are 0.61 μm and 0.25 μm, respectively. Hence, the beam divergent ratio at long and short axis of 2.44:1 was achieved.