Efficient, designable, and broad-bandwidth optical extinction via aspect-ratio-tailored silver nanodisks.

Subwavelength resonators, ranging from single atoms to metallic nanoparticles, typically exhibit a narrow-bandwidth response to optical excitations. We computationally design and experimentally synthesize tailored distributions of silver nanodisks to extinguish light over broad and varied frequency windows. We show that metallic nanodisks are 2-10x more efficient in absorbing and scattering light than common structures, and can approach fundamental limits to broadband scattering for subwavelength particles. We measure broadband extinction per volume that closely approaches theoretical predictions over three representative visible-range wavelength windows, confirming the high efficiency of nanodisks and demonstrating the collective power of computational design and experimental precision for developing new photonics technologies.

Fundamental limits to extinction by metallic nanoparticles.

We show that there are shape-independent upper bounds to the extinction cross section per unit volume of dilute, randomly arranged nanoparticles, given only material permittivity. Underlying the limits are restrictive sum rules that constrain the distribution of quasistatic eigenvalues. Surprisingly, optimally designed spheroids, with only a single quasistatic degree of freedom, reach the upper bounds for four permittivity values. Away from these permittivities, we demonstrate computationally optimized structures that surpass spheroids and approach the fundamental limits.

Incoherent white light solitons in logarithmically saturable noninstantaneous nonlinear media.

We analytically demonstrate the existence of white light solitons in logarithmically saturable noninstantaneous nonlinear media. This incoherent soliton has elliptic Gaussian intensity profile, and elliptic Gaussian spatial correlation statistics. The existence curve of the soliton connects the strength of the nonlinearity, the spatial correlation distance as a function of frequency, and the characteristic width of the soliton. For this soliton to exist, the spatial correlation distance must be smaller for larger temporal frequency constituents of the beam.

Interactions between two-dimensional composite vector solitons carrying topological charges.

We present a comprehensive study of interactions (collisions) between two-dimensional composite vector solitons carrying topological charges in isotropic saturable nonlinear media. We numerically study interactions between such composite solitons for different regimes of collision angle and report numerous effects which are caused solely by the "spin" (topological charge) carried by the second excited mode. The most intriguing phenomenon we find is the delayed-action interaction between interacting composite solitons carrying opposite spins. In this case, two colliding solitons undergo a fusion process and form a metastable bound state that decays after long propagation distances into two or three new solitons. Another noticeable effect is spin-orbit coupling in which angular momentum is being transferred from "spin" to orbital angular momentum. This phenomenon occurs at angles below the critical angle, including the case when the initial soliton trajectories are in parallel to one another and lie in the same plane. Finally, we report on shape transformation of vortex component into a rotating dipole-mode solitons that occurs at large collision angles, i.e., at angles for which scalar solitons of all types simply go through one another unaffected.

Integer and fractional angular momentum borne on self-trapped necklace-ring beams.

We present self-trapped necklace-ring beams that carry and conserve angular momentum. Such beams can have a fractional ratio of angular momentum to energy, and they exhibit a series of phenomena typically associated with rotation of rigid bodies and centrifugal force effects.

Delayed-action interaction and spin-orbit coupling between solitons.

We report on new fundamental phenomena in soliton interactions: delayed-action interaction and "spin"-orbit coupling upon collision between two-dimensional composite solitons carrying topological charges.

Low-loss asymptotically single-mode propagation in large-core OmniGuide fibers.

We present the light-propagation characteristics of OmniGuide fibers, which guide light by concentric multi-layer dielectric mirrors having the property of omnidirectional reflection. We show how the lowest-loss TE_01 mode can propagate in a single-mode fashion through even large-core fibers, with other modes eliminated asymptotically by their higher losses and poor coupling, analogous to hollow metallic microwave waveguides. Dispersion, radiation leakage, material absorption, nonlinearities, bending, acircularity, and interface roughness are considered with the help of leaky modes and perturbation theory, and both numerical results and general scaling relations are presented. We show that cladding properties such as absorption and nonlinearity are suppressed by many orders of magnitude due to the strong confinement in a hollow core, and other imperfections are tolerable, promising that the properties of silica fibers may be surpassed even when nominally poor materials are employed.

Eliminating the transverse instabilities of kerr solitons

We show analytically, numerically, and experimentally that a transversely stable one-dimensional [(1+1)D] bright Kerr soliton can exist in a 3D bulk medium. The transverse instability of the soliton is completely eliminated if it is made sufficiently incoherent along the transverse dimension. We derive a criterion for the threshold of transverse instability that links the nonlinearity to the largest transverse correlation distance for which the 1D soliton is stable.

Self-trapping of "necklace-ring" beams in self-focusing kerr media

Recently, we suggested a type of self-trapped optical beams that can propagate in a stable form in (2+1)D self-focusing Kerr media: Necklace-ring beams [M. Soljacic, S. Sears, and M. Segev, Phys. Rev. Lett. 81, 4851 (1998)]. These self-trapped necklaces slowly expand their ring diameter as they propagate as a result of a net radial force that adjacent "pearls" (azimuthal spots) exert on each other. Here, we revisit the self-trapped necklace beams and investigate their properties analytically and numerically. Specifically, we use two different approaches and find analytic expressions for the propagation dynamics of the necklace beams. We show that the expansion dynamics can be controlled and stopped for more than 40 diffraction lengths, making it possible to start thinking about interaction-collision phenomena between self-trapped necklaces and related soliton effects. Such self-trapped necklace-ring beams should also be observable in all other nonlinear systems described by the cubic (2+1)D nonlinear Shrodinger equation-in almost all nonlinear systems in nature that describe envelope waves.

Bright spatial solitons on a partially incoherent background

We present the first observation of incoherent antidark spatial solitons in noninstantaneous nonlinear media. This new class of soliton states involves bright solitons on a partially incoherent background of infinite extent. In the case where the nonlinearity is of the Kerr type, their existence is demonstrated analytically by means of an exact solution. Computer simulations and experiments indicate that these incoherent antidark solitons can propagate in a stable fashion provided that the spatial coherence of their background is reduced below the incoherent modulation instability threshold.

Composite multihump vector solitons carrying topological charge

We propose composite solitons carrying topological charge: multicomponent two dimensional [ (2+1)D] vector (Manakov-like) solitons for which at least one component carries topological charge. These multimode solitons can have a single hump or exhibit a multihump structure. The "spin" carried by these multimode composite solitons suggests 3D soliton interactions in which the particlelike behavior includes spin, in addition to effective mass, linear, and angular momenta.

Cantor set fractals from solitons

We show how a nonlinear system that supports solitons can be driven to generate exact (regular) Cantor set fractals. As an example, we use numerical simulations to demonstrate the formation of Cantor set fractals by temporal optical solitons. This fractal formation occurs in a cascade of nonlinear optical fibers through the dynamical evolution from a single input soliton.

Self-similarity and fractals in soliton-supporting systems

We describe a principle that can be used to generate self-similarity and fractals in almost any nonlinear system in nature that supports solitons, given that some proper nonadiabatic conditions are met. We illustrate our idea on a particular optics example that also theoretically demonstrates fractals in nonlinear optics.

Modulation instability of incoherent beams in noninstantaneous nonlinear media

We show that modulation instability can exist with partially spatially incoherent light beams in a noninstantaneous nonlinear environment. For such incoherent modulation instability to occur, the value of the nonlinearity has to exceed a threshold imposed by the degree of spatial coherence.

Modulation instability and pattern formation in spatially incoherent light beams.

We report on the experimental observation of modulation instability of partially spatially incoherent light beams in noninstantaneous nonlinear media and show that in such systems patterns can form spontaneously from noise. Incoherent modulation instability occurs above a specific threshold that depends on the coherence properties (correlation distance) of the wave packet and leads to a periodic train of one-dimensional filaments. At a higher value of nonlinearity, the incoherent one-dimensional filaments display a two-dimensional instability and break up into self-ordered arrays of light spots. This discovery of incoherent pattern formation reflects on many other nonlinear systems beyond optics. It implies that patterns can form spontaneously (from noise) in diverse nonlinear many-body systems involving weakly correlated particles, such as atomic gases at (or near) Bose-Einstein condensation temperatures and electrons in semiconductors at the vicinity of the quantum Hall regime.

Effect of gonadectomy on taste preference for glucose solutions in rats.

Mature male and female rats maintained on an ad lib diet were given a choice between tap water and glucose solutions of different concentrations (1, 5 and 12 percent). Both sexes exhibited a definite preference for the 12 percent glucose solution, but the females drank significantly more than males. Gonadectomy produced neither quantitative nor qualitative changes in the choice made by male rats. On the contrary, gonadectomized females showed a depression of the 12 percent glucose solution intake and an increase in the 5 percent glucose solution intake, resulting in a decrease of the total fluid intake. A comparison of ovariectomized and intact female rats in regard to the self-selection of tap water and a 5 percent glucose solution confirmed the stimulatory effect of ovariectomy on the 5 percent glucose solution intake. When a choice between tap water and 12 percent glucose solution was permitted the ovariectomized rats showed a weaker positive response to the sweet solution than the intact female rats.