Abstract

Idealized optical fields of infinite spatial extent and energy can display a number of interesting properties, such as exact longitudinal periodicity,¹ propagation-invariance,² and rotation of the intensity distribution without any scale change.³–⁵ The angular spectra of all these fields consist of one or more rings, known as Montgomery’s rings.¹ Therefore finite-aperture approximations can be realized by placing a filter with a set of concentric ringlike apertures (with appropriate complex-amplitude transmission functions) in the front focal plane of a collimating lens and illuminating the filter with a plane wave — this is a direct extension of the method originally proposed for the generation of propagation-invariant fields.2 However, the method outlined above suffers from poor light efficiency because only a small fraction of the incident light is transmitted by the set of ring apertures. Diffractive optics provides the means to generate propagation-invariant fields with high light efficiency using phase elements analogous to generalized axicons.⁶ In this paper we demonstrate experimentally that quite general rotating and self-reproducing optical fields can also be produced by means of diffractive optics.

© 1998 Optical Society of America