Shaping caustics into propagation-invariant light

Alessandro Zannotti,Mark R Dennis,Mark R Dennis,Cornelia Denz,Miguel A Alonso,Miguel A Alonso,Miguel A Alonso,Miguel A Alonso,Miguel A Alonso

doi:10.1038/s41467-020-17439-3

Abstract

Structured light has revolutionized optical particle manipulation, nano-scaled material processing, and high-resolution imaging. In particular, propagation-invariant light fields such as Bessel, Airy, or Mathieu beams show high robustness and have a self-healing nature. To generalize such beneficial features, these light fields can be understood in terms of caustics. However, only simple caustics have found applications in material processing, optical trapping, or cell microscopy. Thus, these technologies would greatly benefit from methods to engineer arbitrary intensity shapes well beyond the standard families of caustics. We introduce a general approach to arbitrarily shape propagation-invariant beams by smart beam design based on caustics. We develop two complementary methods, and demonstrate various propagation-invariant beams experimentally, ranging from simple geometric shapes to complex image configurations such as words. Our approach generalizes caustic light from the currently known small subset to a complete set of tailored propagation-invariant caustics with intensities concentrated around any desired curve.

Highlights

Structured light has revolutionized optical particle manipulation, nano-scaled material processing, and high-resolution imaging
The conceptual basis for this work is the relation between these wave solutions and the simpler ray model, for which the intensity maxima follow the shapes of the caustics, which are the envelopes of the twoparameter family of rays associated with the field[31]
Propagation invariance requires that all rays travel at the same angle θ with respect to the propagation direction, and that the two-parameter ray family is composed of one-parameter subfamilies of parallel rays constrained to planes parallel to z. This structure guarantees that the caustics themselves are invariant in z, since they correspond to the envelopes of these planes

Summary

Introduction

Structured light has revolutionized optical particle manipulation, nano-scaled material processing, and high-resolution imaging. 1234567890():,; The field of structured light has grown significantly since the early studies of Laguerre- and Hermite-Gaussian modes in laser cavities[1,2] This growth stemmed both from increased theoretical understanding and from the advent of new optical devices such as spatial light modulators (SLMs). The intensity maxima of these beams are localized around the corresponding conic section shapes, characterized by their caustics[24,26,27,28] Some of these propagation-invariant beams have been used in advanced optical trapping setups[16,17,29], imaging with high resolution[14,15], and ultrafast nanoscale material processing with high aspect ratios[10,11,30]. These methods are illustrated with the experimental implementation of beams whose intensity features trace a range of geometrical shapes as well as more complex patterns such as words, which remain essentially invariant over a significant propagation distance

Methods

Results

Conclusion