Self-imaging fields

An analysis is made of nonmonochromatic and monochromatic fields which can reproduce themselves in space. In the paraxial approximation the self-imaging condition is satisfied by fields which are periodic in the transverse cross section and obey certain relationships between their geometric parameters. Some properties of these fields are investigated. It is shown that the fields in plane-mirror resonators are special cases of selfimaging fields considered here and that transverse wave numbers in large-aperture resonators for the optical frequency range have a continuous spectrum of values which have an upper limit in the case of an active resonator because of the existence of an excitation threshold. A report is given of an experimental study of some features of monochromatic self-imaging fields and also of their behavior in the case of aperture restrictions and spatial filtering, i.e., when fields of a resonator with a Fresnel number of 100 is simulated in free space.