Phase-only superresolution elements

A theoretical study of elements that produce superresolution effects is presented. The aim of superresolution is to overcome the limits imposed by diffraction on the performance of optical systems. However, any attempt to increase resolution tends to produce undesirable side effects such as reduced brightness and limited field of view. Phase-only elements are proposed and it is shown that they can be designed for high performance and considerable control of the superresolved pattern. Relevant applications include confocal scanning microscopy and optical disk storage.; The properties of transverse superresolution are investigated. Exact and numerical calculations are employed to determine the space of solutions of annular phase-only structures with a binary and multiphase phase function. Novel optimization techniques are introduced to address constrained design situations. Performance of the phase-only element is compared to other superresolution techniques. Solutions for confocal microscopy indicate that the transverse resolution can be more than doubled. For optical data storage applications effective numerical apertures up to nearly 0.9 can be achieved.; The axial behavior of phase-only elements is also examined. Solutions for axial superresolution that increase the sectioning power in confocal microscopes are determined as well as solutions that increase the focal depth for optical data storage. Multiphase and binary elements are studied numerically and an optimization procedure based on simulated annealing is proposed. Acceptable solutions can reduce the spot size by about 40% with respect to the diffraction limit while maintaining high levels of Strehl ratio and controlled sidelobes.; Parallel to the discovery of superresolution there has been a constant interest in its ultimate limits. Upper bounds are reported that delimit the best performance possible for any rotationally-symmetric element. The performance currently possible with superresolution techniques is compared with the upper bounds. Approaches to achieve the ultimate limits are discussed.; Solutions that exhibit simultaneous superresolution in both axial and transverse directions, or three-dimensional superresolution, are presented. The confinement of the intensity pattern is determined with the three-dimensional point spread function. Designs for confocal scanning microscopy and the limits of three-dimensional superresolution are investigated.