Creation and preservation of superoscillation in a dielectric optical waveguide

Superoscillation refers to a phenomenon where a bandlimited wave locally oscillates faster than its highest Fourier component. Current research on optical superoscillations predominantly lies on the basis of free-space waves. As optical waveguide plays a key role in energy and information transporting, guided waves with precisely controlled deep-subwavelength features offers unprecedented flexibility for applications. In this letter, we numerically show that, by superimposing eigenmodes of a multimode SiO2 waveguide and forcing the resultant field to pass through a set of predetermined points, superoscillatory fields in various shapes can be formed in preset cross-sectional planes. Furthermore, by padding prescribed intensities in multiple crosssections, we successfully create a persistent superoscillatory saddle.