A Ferrofluid Deformable Mirror for Adaptive Optics

Abstract

Increasing multi-disciplinary demand for imaging and optical signal processing modalities with extreme performance capabilities has fueled the adoption of adaptive optics technologies, which synthesize optical systems with suitable properties by manipulating propagating wavefields in closed-loop feedback to combat adverse diffraction effects and dynamic wavefront aberrations. Deformable mirrors are the primary enabling technology for adaptive optics. The challenges associated with high-contrast imaging of Earth-like exoplanets has paced the ongoing rapid advancements in deformable mirror design and modeling. Motivated by this application, this research studies a new ferrofluid deformable mirror concept, including the development of several prototypes and the investigation of the underlying physics and theoretical performance capability through a first-principles approach. The mathematical model illuminates important dimensionless quantities that characterize the susceptibility of the flexible reflective surface to gravitational and fluid-mediated magnetic forces. It also demonstrates the theoretical possibility of using configurable magnetic fields to produce localized bidirectional deformations of the mirror. This work determines the reachable mirror shapes and the degree of controllability of those shapes as well as the relationship of those properties to key design parameters, discusses the fundamental limitations of the ferrofluid deformable mirror concept, and recommends directions for future work.