Phase angle controlled stationary elements for wavefront engineering of electromagnetic radiation

Abstract

A reconfigurable and stationary element for the engineering of the wavefront of electromagnetic radiation. The element includes a phase change material that may be reversibly transformed between its crystalline and amorphous states. By forming a gradient in crystallinity, a phase taper may be stored in the phase change material of the instant element. The phase taper provides control of the phase angle of reflected or reradiated electromagnetic radiation. An incident wavefront of electromagnetic radiation interacts with the instant element and is reradiated with controlled propagation characteristics imposed by the stored phase taper. The instant element may provide non-specular reflection, beam steering, focusing, defocusing, symmetrical and asymmetrical cross section effects, and wavefront correction. In a preferred embodiment, a pattern of amorphous marks is formed within a crystalline matrix of phase change material. By controlling the size, shape, spacing, symmetry and distribution of marks, crystallinity gradients of various strengths in one or more directions may be formed to provide phase tapers that effect the engineering of wavefronts. An apparatus for forming patterns of marks included in the instant element is also provided.