A tunable liquid-crystal microlens with hybrid alignment

A tunable liquid-crystal microlens with hybrid alignment was fabricated using micro-imprinting technology. The imprinted hybrid alignment, which was surrounded by homogeneous (homeotropic) alignment, resulted in spatial refractive-index distribution of liquid-crystal molecules in the microlens. With different hybrid-alignment configurations, the microlens functioned either as a convex or concave lens. The focal length of the microlens was electrically controlled at applied voltages of less than 4 V. The focal length was adjusted from 7.8 to 8.6 mm and from -10 to -35 mm for a convex and a concave lens, respectively. The rising response time was 0.5 s, and the falling response time was 5 s.