Fast Quasi-static Beam Steering via Conformally-Mapped Gratings

Fast beam steering is useful in applications including free space optical switching and communications. Quasi-static beam steering, where the beam rapidly switches between discrete fixed directions, presents special challenges. Here we demonstrate a fast quasi-static 'pinwheel' scanner by conformally mapping linear blazed gratings into curved structures fabricated onto annular sections of a rotary disk. We use Matlab and Zemax to model the effects of the conformally-mapped grating on the emitted optical beam. We show a specific two-dimensional (2D) 'pinwheel' scanner design with 56 gratings, each deflecting 1.31 mu m incident light by 11.3 degrees in one of four directions with 75% optical efficiency. The element was fabricated by optical grey-scale lithography on a 95 mm diameter substrate, coated with gold, and mounted onto the spindle of a 3.5" format 7200 rpm magnetic disk drive. We characterize the optical beam steering efficiency, pointing, and stability, and demonstrate microsecond switching speed of a single mode fiber signal.