![]() ![]() As a result, there has been a long-standing fascination with so-called ‘diffraction-free’ beams whose change in shape and scale during propagation is curbed 2. Diffraction sets limits on the optical resolution in microscopy, lithography and photography, on the maximum distance for free-space optical communications and standoff detection, and on the precision of spectral analysis 1. These ‘space–time’ light sheets can be useful in microscopy, nonlinear spectroscopy, and non-contact measurements.ĭiffractive spreading is a fundamental feature of freely propagating optical beams that is readily observed in everyday life. Far from being exceptional, self-similar axial-propagation in free space is a generic feature of fields whose spatial and temporal degrees of freedom are tightly correlated. The spectral loci of such beams are the reduced-dimensionality trajectories at the intersection of the light-cone with spatiotemporal spectral planes. ![]() By introducing programmable conical (hyperbolic, parabolic or elliptical) spectral correlations between the beam’s spatiotemporal degrees of freedom, a continuum of families of propagation-invariant light sheets is generated. Here, we demonstrate that the temporal degree of freedom can be exploited to efficiently synthesize one-dimensional pulsed light sheets that propagate self-similarly in free space, with no need for nonlinearity or dispersion. Monochromatic beams that avoid diffractive spreading require two-dimensional transverse profiles and there are no corresponding solutions for profiles restricted to one transverse dimension. Diffraction-free optical beams propagate freely without change in shape and scale. ![]()
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