Abstract
Recently we introduced the class of highly localized wavepackets (HLWs) as a generalization of optical Bessel-like needle beams. Here we report on the progress in this field. In contrast to pulsed Bessel beams and Airy beams, ultrashort-pulsed HLWs propagate with high stability in both spatial and temporal domain, are nearly paraxial (supercollimated), have fringe-less spatial profiles and thus represent the best possible approximation to linear “light bullets”. Like Bessel beams and Airy beams, HLWs show self-reconstructing behavior. Adaptive HLWs can be shaped by ultraflat three-dimensional phase profiles (generalized axicons) which are programmed via calibrated grayscale maps of liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs). Light bullets of even higher complexity can either be freely formed from quasi-continuous phase maps or discretely composed from addressable arrays of identical nondiffracting beams. The characterization of few-cycle light bullets requires spatially resolved measuring techniques. In our experiments, wavefront, pulse and phase were detected with a Shack-Hartmann wavefront sensor, 2D-autocorrelation and spectral phase interferometry for direct electric-field reconstruction (SPIDER). The combination of the unique propagation properties of light bullets with the flexibility of adaptive optics opens new prospects for applications of structured light like optical tweezers, microscopy, data transfer and storage, laser fusion, plasmon control or nonlinear spectroscopy.
Highlights
The localization of ultrashort and ultrabroadband pulses in spatial and temporal domain is a challenge for ultrashort pulse laser physics because of the fundamental aspects as well as the enormous application potential, e.g., in microscopy, spectroscopy or optical communication, to mention only a few
The conditions for the formation of certain types of light bullets were studied theoretically and experimentally. Most of these papers were focused on the specific interactions of light and a medium and can be separated in two basically different approaches: (a) nonlinear light bullets and (b) linear light bullets. While this main stream of works evolved from nonlinear optics, a quite other approach to linear light bullets already existed in the frame of general wave physics and provided, in reverse direction, new impetus straight back to the soliton theory
The solitary or multiple light bullets are of radially symmetric and non-symmetric structure belong to the classes of above discussed pulsed needle beams and highly localized wavepackets (HLWs)
Summary
The localization of ultrashort and ultrabroadband pulses in spatial and temporal domain is a challenge for ultrashort pulse laser physics because of the fundamental aspects as well as the enormous application potential, e.g., in microscopy, spectroscopy or optical communication, to mention only a few. A stable propagation of localized wavepackets over large distances requires an appropriate mechanism to continually compensate for the divergence. This can be obtained by balancing dispersion and diffraction effects as known from soliton formation [1,2,3,4]. Most of these papers were focused on the specific interactions of light and a medium and can be separated in two basically different approaches: (a) nonlinear light bullets and (b) linear light bullets While this main stream of works evolved from nonlinear optics (preferentially of fibers and waveguides), a quite other approach to linear light bullets already existed in the frame of general wave physics and provided, in reverse direction, new impetus straight back to the soliton theory. We present our most recent results including the adaptive generation, characterization and application of near infrared ultrashort-pulsed Bessel-like needle beams, highly localized wavepackets and complex nondiffracting patterns at pulse durations corresponding to just a few cycles of the optical field
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