Soft matter – from polymers over molecular assemblies up to cells – exhibit unique mechanical properties, as being easily deformable under external forces. When subject to optical forces, they may on the one hand be analyzed in their features as viscoelasticity or scattering. On the other hand, complex light may transfer momentum or orbital angular momentum to soft matter, allowing to arrange, structure, and assemble functional particles. In this keynote, we showcase examples of optical trapping of droplets, viscoelastic complex matter, active swimmers, and cells, and demonstrate the versatile features of interaction of light with soft matter from analysis to control.
Light propelled micro-machines yield important advantages. While most other propulsion mechanisms require some kind of fuel in the surrounding medium, light acts as an external energy source which enables high spatio-temporal control. In our novel approach the actuation emerges from refraction of light on micro-machines with an asymmetric shape and refractive index profiles. The artificial micro-machines are fabricated by femtosecond laser lithography by two-photon polymerization which enables high precision and flexibility. We demonstrate and compare the propulsion of light propelled particles with different geometries and refractive index gradients.
Among the numerous propulsion mechanisms developed in the past to self-propelled nano- and micro particles, light-driven machines are most promising, since they enable a natural spatio-temporal control of the motion. We report a novel fuel-free propulsion mechanism induced by an external light stimulus. The actuation relies on refraction of light, while the net propulsion force emerges from an asymmetric particle shape and a symmetry-broken refractive index profile. Two-photon polymerization is employed for fabrication of the artificial machines, whose geometries and refractive index profiles are optimized with the help of numerical simulations. We demonstrate the directional movement of refractive light-propelled particles, and the increased performance of artificial refractive index machines.
Artificial active nano- and microparticles driven by light are of special interest since their propulsion can easily be controlled via the illumination. Recently, we have established a propulsion mechanism based on asymmetric light refraction caused by a refractive-index gradient. We will introduce into this new approach based on two-photon polymerization of the active particles, and demonstrate active propulsion under illumination as well as pattern formation in colloidal suspensions of these active particles controlled by light.
Nature holds situations in which sudden changes are caused by smooth alterations. The famous Airy and Pearcey beams represent diffraction patterns of corresponding fold and cusp bifurcations, respectively. When classified in a hierarchical order, they are subsequently followed by swallowtail and butterfly beams. These beams are generally characterized as cuspoid beams, accelerated on bent trajectories. They lead to various applications, among them the realization of curved waveguides. Their umbilic counterparts, however, characterized by even more complex diffraction patterns, have up to now only been characterized, but not yet been utilized as functional fabrication templates for applications in photonics.
In this contribution, we present our results on embedding higher-order cuspoid and umbilic catastrophes in tailored light. These light structures show versatile curved strands of high intensity during propagation. The elliptic umbilic beam even morphs from a hexagonal transverse intensity pattern to a beam with a single central hot spot to become again the original hexagonal pattern. We thus exploit the dynamics of these caustics to optically induce corresponding photonic lattices in nonlinear media and demonstrate light propagation in elliptic umbilic lattices.
Our approach enables fabricating continuously transforming lattices with varying band structure, paving the way for advanced topological photonics.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.