Broadband spatiotemporal axicon fields.

We study the properties of broadband optical fields produced by two classes of axicons: reflective axicons creating fields with a frequency-independent cone angle, and diffractive axicons that generate fields with frequency-independent transverse scale. We also consider two different types of illumination: spectrally completely coherent pulses and spectrally incoherent (stationary) light assuming that the spectra are the same in both situations. In the former case we evaluate the spatiotemporal shape of the output field, and in the latter case its spatiotemporal coherence properties. Physical reasons for the substantially different fields produced by the two types of axicons are identified. Our results are useful for optical applications in which joint spatial and temporal field localization is desired.