Enhanced inverse Faraday effect and time-dependent thermo-transmission in gold nanodisks.

Nonmagnetic media can be magnetized by light via processes referred to as an inverse Faraday effect (IFE). With nonmagnetic metal nanostructures, the IFE is dominated by the presence of light-induced solenoidal surface currents or plasmons with orbital angular momenta, whose properties depend on both the light and nanostructure geometry. Here, through a systematic study of gold nanodisks with different sizes, we demonstrate order-of-magnitude enhancement of the IFE compared to a bare gold film.

Unveiling Enhanced Electrostatic Repulsion in Silica Nanosphere Assembly: Formation Dynamics of Body-Centered-Cubic Colloidal Crystals.

We demonstrate the effective establishment of long-range electrostatic interactions among colloidal silica nanospheres through acid treatment, enabling their assembly into colloidal crystals at remarkably low concentrations. This novel method overcomes the conventional limitation in colloidal silica assembly by removing entrapped NH ions and enhancing the electrical double layer (EDL) thickness, offering a time-efficient alternative to increase electrostatic interactions compared with methods like dialysis. The increased EDL thickness facilitates the assembly of SiO nanospheres into a body-centered-cubic lattice structure at low particle concentrations, allowing for broad spectrum tunability and high tolerance to particle size polydispersity.

Fractal, diffraction-encoded space-division multiplexing for FSO with misalignment-robust, roaming transceivers.

For free space optical (FSO) communication, a small misalignment of the transceivers may result in link failure or severe performance degradation. It can be difficult to track the narrow optical beams over long distances. Here, we propose "diffractal space-division multiplexing" (DSDM), an FSO transmission system capable of supporting misaligned roaming transceivers.

Insect-inspired nanofibrous polyaniline multi-scale films for hybrid polarimetric imaging with scattered light.

We demonstrate a bio-inspired coating for novel imaging and sensing designs: the coating sorts different colors and linear polarizations. This coating, composed of conducting, nanofibrous polyaniline in an inverse opal film (PANI-IOF), is inexpensive and can feasibly be deposited over large areas on a range of flexible and non-flat substrates. With PANI IOFs, light is scattered into azimuthally polarized Debye rings.

Broadband chiral hybrid plasmon modes on nanofingernail substrates.

There is significant interest in the utility of asymmetric nanoaperture arrays as substrates for the surface-enhanced detection, fluorescence, and imaging of individual molecules. This work introduces obliquely-cut, out-of-plane, coaxial layered structures on an aperture edge. We refer to these structures as nanofingernails, which emphasizes their curved, oblique, and out-of-plane features.

Improved Anisotropic Thermoelectric Behavior of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) via Magnetophoresis.

There is strong demand for achieving morphological control of conducting polymers in its many potential applications, from energy harvesting to spintronics. Here, the static magnetic-field-induced alignment of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) particles is demonstrated. PEDOT:PSS thin films cast under modest mT-level magnetic fields exhibit a fourfold increase in the Seebeck coefficient and doubled electrical conductivity.

Solvent Retention and Crack Evolution in Dropcast PEDOT:PSS and Dependence on Surface Wetting.

The drying of nanocolloidal polymers is governed by the interplay among surface tension, evaporation, and contact-line pinning, among other phenomena. Here, we describe the sequential evolution of poly-3,4-ethylenedioxythiophene:poly(styrene sulfonate) (PEDOT:PSS) through two distinct regimes evidenced by annular or radial cracking and show that the cracking dynamics and solvent-retention postdrying and postcracking are mediated by wetting to the substrate surface. The corresponding changes in the PEDOT:PSS morphology are also observed to relate to the radial or cracking dynamics.

Long-Range Self-Assembly via the Mutual Lorentz Force of Plasmon Radiation.

Long-range interactions often proceed as a sequence of hopping through intermediate, statistically favored events. Here, we demonstrate predictable mechanical dynamics of particles that arise from the Lorentz force between plasmons. Even if the radiation is weak, the nonconservative Lorentz force produces stable locations perpendicular to the plasmon oscillation; over time, distinct patterns emerge.

Meta-Optical Chirality and Emergent Eigen-polarization Modes via Plasmon Interactions.

The response of an individual meta-atom is often generalized to explain the collective response of a metasurface in a manner that neglects the interactions between meta-atoms. Here, we study a metasurface composed of tilted achiral meta-atoms with no spatial variation of the unit cell that derives appreciable optical chirality solely from the asymmetric interactions between meta-atoms. The interactions between meta-atoms are considered to stem from the Lorentz force arising from the Larmor radiation of adjacent plasmonic resonators because their inclusion in a simple model accurately predicts the bonding/anti- bonding modes that are measured experimentally.

Control of photo-induced voltages in plasmonic crystals via spin-orbit interactions.

There is wide interest in understanding and leveraging the nonlinear plasmon-induced potentials of nanostructured materials. We investigate the electrical response produced by spin-polarized light across a large-area bottom-up assembled 2D plasmonic crystal. Numerical approximations of the Lorentz forces provide quantitative agreement with our experimentally-measured DC voltages.

Robustness and spatial multiplexing via diffractal architectures.

When plane waves diffract through fractal-patterned apertures, the resulting far-field profiles or diffractals also exhibit iterated, self-similar features. Here we show that this specific architecture enables robust signal transmission and spatial multiplexing: arbitrary parts of a diffractal contain sufficient information to recreate the entire original sparse signal.

Pulse splitting in the anomalous group-velocity-dispersion regime.

We investigate experimentally the role that the initial temporal profile of ultrashort laser pulses has on the self-focusing dynamics in the anomalous group-velocity dispersion (GVD) regime. We observe that pulse-splitting occurs for super-Gaussian pulses, but not for Gaussian pulses. The splitting does not occur for either pulse shape when the GVD is near-zero.

Dynamics of elliptical beams in the anomalous group-velocity dispersion regime.

We investigate 3D spatio-temporal focusing of elliptically-shaped beams in a bulk medium with Kerr nonlinearity and anomalous group-velocity dispersion (GVD). Strong space-time localization of the mode is observed through multi-filamentation with temporal compression by a factor of 3. This behavior is in contrast to the near-zero GVD regime in which minimal pulse temporal compression is observed.

Spectral reshaping and pulse compression via sequential filamentation in gases.

We provide a theoretical description of the spatio-temporal dynamics of sequential filamentation in noble gases that can lead to pulse compression down to nearly single-cycle pulses. We show that the strong pulse compression occurs as a result of serially-generated on-axis filaments and spectral filtering of an extensive blue-shifted compressible spectra. We show that the dynamics of this sequential filamentation can be readily tuned by varying the gas pressure and can be scaled to various pulse energies.

Self-focusing dynamics of polarization vortices in Kerr media.

We investigate numerically and experimentally the spatial collapse dynamics and polarization stability of radially and azimuthally polarized vortex beams in pure Kerr medium. These beams are unstable to azimuthal modulation instabilities and break up into distinct collapsing filaments. The polarization of the filaments is primarily linear with weak circular components at the filaments' boundaries.

Collapse and stability of necklace beams in Kerr media.

We investigate the spatial dynamics of optical necklace beams in Kerr media. For powers corresponding to less than the critical power for self-focusing per bead, we experimentally confirm the confinement of these necklace beams as proposed in [Phys. Rev.

Collapse dynamics of super-Gaussian Beams.

We investigate the self-focusing dynamics of super-Gaussian optical beams in a Kerr medium. We find that up to several times the critical power for self-focusing, super-Gaussian beams evolve towards a Townes profile. At higher powers the super-Gaussian beams form rings which break into filaments as a result of noise.

Collapse of optical vortices.

We theoretically and experimentally investigate the self-focusing of optical vortices in Kerr media. We observe collapse to a distinct self-similar profile, which becomes unstable to azimuthal perturbations. We analyze the azimuthal modulational instability for ring-shaped vortices and predict the number of azimuthal maxima solely as a function of power and topological charge.