Metal nanoparticles with sharp corners: Universal properties of plasmon resonances

We predict the simultaneous occurrence of two fundamental phenomena for metal nanoparticles possessing sharp corners: First, the main plasmonic dipolar mode experiences strong red shift with decreasing corner curvature radius; its resonant frequency is controlled by the apex angle of the corner and the normalized (to the particle size) corner curvature. Second, the split-off plasmonic mode experiences strong localization at the corners. Altogether, this paves the way for tailoring of metal nano-structures providing wavelength-selective excitation of localized plasmons and a strong near-field enhancement of linear and nonlinear optical phenomena

Chirped dissipative solitons of the complex cubic-quintic nonlinear Ginzburg-Landau equation

Approximate analytical chirped solitary pulse (chirped dissipative soliton) solutions of the one-dimensional complex cubic-quintic nonlinear Ginzburg-Landau equation are obtained. These solutions are stable and highly-accurate under condition of domination of a normal dispersion over a spectral dissipation. The parametric space of the solitons is three-dimensional, that makes theirs to be easily traceable within a whole range of the equation parameters. Scaling properties of the chirped dissipative solitons are highly interesting for applications in the field of high-energy ultrafast laser physics.Comment: 20 pages, 12 figures, the mathematical apparatus is presented in detail in http://info.tuwien.ac.at/kalashnikov/NCGLE2.htm

Selective excitation of plasmons superlocalized at sharp perturbations of metal nanoparticles

Sharp metal corners and tips support plasmons localized on the scale of the curvature radius -- superlocalized plasmons. We analyze plasmonic properties of nanoparticles with small and sharp corner- and tip-shaped surface perturbations in terms of hybridization of the superlocalized plasmons, which frequencies are determined by the perturbations shape, and the ordinary plasmons localized on the whole particle. When the frequency of a superlocalized plasmon gets close to that of the ordinary plasmon, their strong hybridization occurs and facilitates excitation of an optical hot-spot near the corresponding perturbation apex. The particle is then employed as a nano-antenna that selectively couples the free-space light to the nanoscale vicinity of the apex providing precise local light enhancement by several orders of magnitude

Nonlinear optical pulses in media with asymmetric gain

A generic novel model governing optical pulse propagation in a nonlinear dispersive amplifying medium with asymmetric (linear spectral slope) gain is introduced. We examine the properties of asymmetric optical pulses formed in such gain-skewed media, both theoretically and numerically. We derive a dissipative optical modification of the classical shallow water equations that highlights an analogy between this phenomenon and hydrodynamic wave-breaking. We observe the development of spectral optical shock waves, and discuss the conditions and origins of this spectral wave-breaking in media with asymmetric gain. These findings provide insight into the nature of asymmetric optical pulses capable of accumulating large nonlinear phase without wave-breaking, a crucial aspect in the design of nonlinear fiber amplifiers.Comment: 11 pages, 10 figure

Random mode coupling assists Kerr beam self-cleaning in a graded-index multimode optical fiber

In this paper, we numerically investigate the process of beam self-cleaning in a graded-index multimode optical fiber, by using the coupled-mode model. We introduce various models of random linear coupling between spatial modes, including coupling between all modes, or only between degenerate ones, and investigate the effects of random mode coupling on the beam self-cleaning process. The results of numerical investigations are in complete agreement with our experimental data

Eigen modes for the problem of anomalous light transmission through subwavelength holes

We show that the wide-spread concept of optical eigen modes in lossless waveguide structures, which assumes the separation on propagating and evanescent modes, fails in the case of metal-dielectric structures, including photonic crystals. In addition to these modes, there is a sequence of new eigen-states with complex values of the propagation constant and non-vanishing circulating energy flow. The whole eigen-problem ceases to be hermitian because of changing sign of the optical dielectric constant. The new anomalous modes are shown to be of prime importance for the description of the anomalous light transmission through subwavelength holes.Comment: 5 pages, 4 figure