[en] We obtain an expression for the matrix element for scattering of a twisted (Laguerre–Gaussian profile) photon from a hydrogen atom. We consider photons incoming with an orbital angular momentum (OAM) of ℓħ, carried by a factor of e^iℓϕ not present in a plane-wave or pure Gaussian profile beam. The nature of the transfer of +2ℓ units of OAM from the photon to the azimuthal atomic quantum number of the atom is investigated. We obtain simple formulas for these OAM flip transitions for elastic forward scattering of twisted photons when the photon wavelength λ is large compared with the atomic target size a, and small compared with the Rayleigh range z_R, which characterizes the collimation length of the twisted photon beam. (paper)

[en] Here, we present a computational tool for optical tweezers which calculates the particle tracking signal measured with a quadrant detector and the shot-noise limit to position resolution. The tool is a piece of Matlab code which functions within the freely available Optical Tweezers Toolbox. It allows the measurements performed in most optical tweezer experiments to be theoretically characterized in a fast and easy manner. The code supports particles with arbitrary size, any optical fields and any combination of objective and condenser, and performs a full vector calculation of the relevant fields. Example calculations are presented which show the tracking signals for different particles, and the shot-noise limit to position sensitivity as a function of the effective condenser NA. (paper)

[en] We analyze the transverse structure of the phase shift in Gaussian light beams. The phase shift is maximal along the axis of propagation of the beam, where it equals the traditional Gouy phase shift, and decreases with increasing distance from the axis, becoming negative beyond the Gouy radius r_G. Physically, we show that the Gouy radius represents the boundary between the propagating (classically allowed) region of the photon beam and the evanescent (forbidden or tunneling) zone. At the beam waist, r_G is precisely the bream width w(0), but the Gouy radius increases as one moves along the path of the beam. The paraxial approximation for the Gouy radius is shown to be valid at all propagation distances z short of the Rayleigh range z_R, where the Gouy radius diverges. The transverse structure and Gouy radius should be particularly important for photon beams carrying orbital angular momentum, where the intensity vanishes on the beam axis. (paper)

[en] An all-optical tunable rainbow-trapping-like effect is realized theoretically in a plasmonic slot waveguide with a chirped nanograting, permeated with organic polymer made of poly(hexafluoropropylene oxide) doped with cholesteryl iodide. Gradually increasing the grating period ensures that the stop band edge of the surface plasmon polariton mode varies with position along the nanograting, which brings about the rainbow-trapping-like effect. The physical mechanism underlying the all-optical tunability of this effect is attributed to the variation in the dispersion relations of the surface plasmon polariton mode caused by the pump laser induced refractive index change of cholesteryl iodide. A shift of up to 17 μm in the trapped position of the surface plasmon polariton mode is achieved under excitation of a 450 mJ cm⁻² pump laser. (paper)

[en] We present the propagation characteristics of y-polarized coupled surface plasmon polariton (SPP) modes supported by ferroelectric polyvinylidene fluoride (PVDF) slab waveguides at terahertz (THz) frequencies. Employing a two-dimensional (2D) finite-element method, four y-polarized coupled SPP modes are obtained, where two modes exhibit long propagation lengths (∼700 μm) and the others provide subwavelength confinement. It is shown that PVDF is a promising material for plasmon-like excitation in the terahertz regime and results in strong confinement of THz wave propagation in SPP-based coupled waveguides. (paper)

[en] We investigate the density of states for a photon gas confined in a nonmagnetic metamaterial medium in which some components of the permittivity tensor are negative. We study the effect of the resulting hyperbolic dispersion relations on the black body spectral density. We show that for both of the possible wavevector space topologies, the spectral density vanishes at a certain frequency. We obtain the partition function and derive some thermodynamical quantities of the system. To leading order, the results resemble those of a one- or two-dimensional photon gas with an enhanced density of states. (paper)

[en] We theoretically analyze the near-infrared properties of a chiral metamaterial constituting an array of twisted crosses and complementary crosses made of silver. Through rigorous full-wave numerical simulations, we demonstrate that this type of metamaterial exhibits wideband giant optical activity, with a polarization azimuth rotation angle reaching values as large as 1900^∘ per wavelength. Owing to the negligible loss at optical frequencies in the dielectric (magnesium fluoride) making up the metamaterial, we observe negligible circular dichroism and low dispersion of the polarization azimuth rotation angle over a wide frequency band. We envision that this type of chiral metamaterial will find extensive applications in optical communication systems and biological sensing. (paper)

[en] In the present work, we highlight the significant effect that the simplest beyond-nearest-neighbor interactions can have on two-dimensional dynamical lattices. To do so, we select as our case example the closest further neighbor, namely the diagonal one, and a prototypical nonlinear lattice, the discrete nonlinear Schrödinger equation. Varying solely the strength of this extra neighbor interaction, we see examples of (a) destabilization of states that start out as stable in the nearest-neighbor limit; (b) stabilization of states that start out as unstable in that limit; (c) bifurcation of novel states that do not exist in the nearest-neighbor case. These dramatic changes are first theoretically highlighted through an analysis of a reduction of the problem to a few excited sites and the associated set of conditions that govern their existence and their dynamical stability. Then, they are corroborated numerically through fixed point computations, spectral analysis and nonlinear dynamical evolution simulations. (paper)

[en] Space-variant inhomogeneously polarized field formed due to superposition of orthogonally polarized Gaussian (LG₀₀) and Laguerre–Gaussian (LG₀₁) beams results in polarization singular beams with different morphology structures such as lemon, star and dipole patterns around the C-point in the beam cross-section. The Pancharatnam–Berry phase plays a critical role in the formation and characteristics of these spatially inhomogeneous fields. We present our experimental results wherein we measure the variable geometric phase by tracking the trajectory of the component vortices in the beam cross-section, by interfering with selective polarization states and by tracking different latitudes on the Poincaré sphere without the effect of a dynamic phase. (paper)

[en] We study the dynamics of polarization singularities in the superposition of two off-axis optical vortices with orthogonal polarization states. The motion of C points, states of circular polarization, is described by varying parameters such as separation distance, constant phase difference and topological charge. We analyze the zeros of the Stokes parameters and find analytical solutions for particular cases. The results could be used to realize an alternative method to measure the vortex topological charge. (paper)