How to better focus waves by considering symmetry and information loss

Abstract

SignificanceWith applications from electromagnetic communications, to biological and astronomical imaging, to lithography and warfare, waves transmit information, and optimal wave focusing is essential. Here we demonstrate the need to amend the belief that spherical or cylindrical wavefronts necessarily focus at their center of curvature. Instead the effective focus shifts toward the source with decreasing apertures, producing astigmatism when, as increasingly shown for modern applications, the wavefronts are not axially symmetric. This leads to significant degradation of axial resolution in nonaxisymmetric light-focusing applications. These conclusions, derived from diffraction theory and validated by application to optical bioimaging, offer a general strategy to likewise improve the resolution of virtually any other wave-based application whose efficacy depends on focusing energy to points or lines.

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