Etienne Brasselet

Self‐assembly of nano‐ and microstructures in soft materials enables stimuli‐responsive functionalities, yet scalable bottom‐up approaches that combine high spatial precision with robust solid‐state architectures remain limited. Liquid crystals provide a versatile platform due to their ability to host topological defects with well‐defined optical and mechanical properties. Here, we introduce a field‐induced nematodynamic templating strategy to program liquid crystal coatings prior to photopolymerization. Resonant standing waves generate large‐area lattices of topological defects that are permanently encoded into a polymer network with high fidelity. The resulting coatings exhibit defect‐specific surface topographies that are reversibly tunable with temperature, while preserving their ability to generate optical vortices and enabling thermally controlled phase and spectral responses. These results demonstrate that topological defects act as programmable units coupling optical and mechanical functionalities within a single platform. Beyond optics, the approach further enables spatial functionalization through guided incorporation of fluorescent particles, highlighting its potential for multifunctional coatings. This defect‐encoded and field‐programmable strategy provides a scalable route toward reconfigurable flat optics, adaptive surfaces, and sensing platforms.

Structured light offers a promising solution for the increasing data demands of modern optical networks, opening up degrees of freedom that can be leveraged for greater channel capacity and more bits per photon. However, its implementation is hindered by real-world distortions, for example, atmospheric turbulence in free space, with severe and rapidly evolving phase perturbations that alter the amplitude, phase, and vectorial polarization structure of the beam. Here, we demonstrate that optical topologies in the form of skyrmions are highly resilient to the effects of real-world atmospheric turbulence. We create and transmit these particle-like topologies of light through a 270-meter free-space optical link, revealing their robustness across a wide variety of conditions and turbulence strengths. While we observe severe distortion in the states’ underlying degrees of freedom, we show that the topological numbers are preserved in all cases. We account for fast changes to the medium, where the channel produces statistically averaged outcomes, by probing the state’s decoherence, showing that while the degree of polarization consequently decays, the topology remains intact. Using topology, we show that information can be transmitted through the channel with almost perfect fidelity (>98%) in most cases, only decreasing to 86% in the most severe conditions tested. This work idemonstrates the potential for optical topologies as reliable and robust information carriers in a real-world environment and points to the potential for other complex channels too, offering attractive features for classical and quantum communication alike.

Torsion pendulums offer exceptional torque sensitivity but inherently suffer from slow response times, limiting time-resolved measurements. We present a single-period, self-resetting optical torque sensor based on a silk fiber torsion pendulum operating in ultra-high vacuum. This non-resonant, time-domain approach enables the detection of discrete optical torque pulses at the attonewton-meter level within seconds, without high quality factors or active damping. The pendulum’s intrinsic mechanical relaxation provides a natural reset between measurements, allowing successive readings. We validate the method using radiation-pressure torque from a laser beam and demonstrate its practicality by measuring solar radiation pressure, providing a compact platform for dynamic optomechanical force sensing.

Spatially structured light has enabled advanced topological and vectorial control, while spatiotemporal manipulation has so far remained largely restricted to scalar phase engineering. Here, we introduce a geometric-phase method for shaping spatiotemporal vectorial beams using q-plates of arbitrary topological charge. We develop an analytical framework describing the polarization-controlled generation of vector beams and polarization skyrmions in the space-time or momentum-time domain and experimentally validate it using an electrically tunable liquid-crystal q-plate. Our results establish q-plates as compact and reconfigurable platforms for vectorial topological shaping of ultrashort pulses, opening directions in spatiotemporal photonics.

We report a nondissipative optomechanical approach to separate the spin and orbital components of transverse energy flows of light beams. Focusing on uniformly polarized paraxial fields, the method relies on detecting the radiation-pressure-induced reorientation of the optical axis in anisotropic media—specifically, liquid crystals. Within a perturbative analytical approach, we demonstrate the selective encoding of the transverse spin and orbital components of the Poynting vector into orthogonal orientational elastic modes, whose relative weights are mediated by the Gouy phase. The spatial distributions of spin and orbital momentum can therefore be retrieved without resorting to point-by-point measurements using absorbing or scattering probe particles. Analytical results are supported by a fully self-consistent numerical solution coupling Maxwell’s equations and Landau-de Gennes nematodynamics in three dimensions. This exact framework captures higher-order and nonparaxial effects beyond the analytical perturbative regime and allows us to validate the predicted Gouy-phase-mediated optomechanical response. These results establish a practical route toward optomechanical imaging of the internal momentum structure of light, fostering momentum-resolved optical metrology and light-matter interaction studies with structured beams.

We report universal skyrmionic spin textures in the cores of optical and acoustic vortex beams, described within the framework of Laguerre-Gaussian modes. We analytically demonstrate nondiffractive propagating spin merons, independent of whether the field is transverse or longitudinal, with their sign controlled by the wavefront helicity. Experimental confirmation is provided in acoustics through full three-dimensional measurements of the velocity vector field. Although these phenomena are intrinsic to vortex cores, we also show that the claimed universality breaks down for higher-order topological charges, depending on the carrier mode, here exemplified using the Bessel framework.

We propose a spin-orbit strategy for generating dual-wavelength quantum skyrmions realized either as entangled photon pairs at dual wavelengths or as heralded single-photon states at a given wavelength-regimes neither previously conceptualized nor demonstrated. By coupling a two-photon entangled state to an electrically tunable liquid crystal topological defect, we engineer both nonlocal and local skyrmionic topologies in a reconfigurable platform. We highlight with examples how this approach may open new directions for engineered topological quantum states that exploit the topological richness of liquid crystals.