Plasmonic Tamm states: second enhancement of light inside the plasmonic waveguide

A type of Tamm states inside metal-insulator-metal (MIM) waveguides is proposed. An impedance based transfer matrix method is adopted to study and optimize it. With the participation of the plasmonic Tamm states, fields could be enhanced twice: the ffirst is due to the coupling between a normal waveguide and a nanoscaled plasmonic waveguide and the second is due to the strong localization and field enhancement of Tamm states. As shown in our 2D coupling configuration, |E|^2 is enhanced up to 1050 times when 1550 nm light is coupled from an 300 nm Si slab waveguide into an 40 nm MIM waveguide.Comment: 3 pages, 4 figure

A nonlinear analytical model for tensile failure prediction of pseudo-ductile composite laminates

In this study, the tensile nonlinear responses of composite laminates with [±θn] s and [±θn∕0] s layups are investigated. An analytical model that integrates the progressive failure, shear nonlinearity, fiber rotation, and fragmentation is established to characterize the nonlinear tensile behavior. A nonlinear factor is used to describe the shear nonlinearity of the resin matrix, which is governed by shear stress, while progressive damage indexes are determined by normal stresses. The degree of fiber rotation and the fragmentation between layers are analytically formulated. Tensile results from experiments conducted in this study and from others in the literature are used to verify the model’s prediction accuracy. The proposed model provides acceptably good predictions of nonlinear behavior for pseudo-ductile carbon fiber reinforced composite laminates. A sensitivity analysis shows that the dominant model parameter changes from axial modulus to shear modulus, and eventually to transverse modulus as the off-axial angle increases from 0◦ to 9

Optical force-induced nonlinearity and self-guiding of light in human red blood cell suspensions

Osmotic conditions play an important role in the cell properties of human red blood cells (RBCs), which are crucial for the pathological analysis of some blood diseases such as malaria. Over the past decades, numerous efforts have mainly focused on the study of the RBC biomechanical properties that arise from the unique deformability of erythrocytes. Here, we demonstrate nonlinear optical effects from human RBCs suspended in different osmotic solutions. Specifically, we observe self-trapping and scattering-resistant nonlinear propagation of a laser beam through RBC suspensions under all three osmotic conditions, where the strength of the optical nonlinearity increases with osmotic pressure on the cells. This tunable nonlinearity is attributed to optical forces, particularly the forward scattering and gradient forces. Interestingly, in aged blood samples (with lysed cells), a notably different nonlinear behavior is observed due to the presence of free hemoglobin. We use a theoretical model with an optical force-mediated nonlocal nonlinearity to explain the experimental observations. Our work on light self-guiding through scattering bio-soft-matter may introduce new photonic tools for noninvasive biomedical imaging and medical diagnosis.Comment: 20 Pages, 5 figures, accepted for publication in Light, Science & Applicatio

Reduced radiation losses in electron beam excited propagating plasmons

Except for heating losses in metal, propagating plasmons also suffer a lot from radiation losses. In this paper, electron beams are proposed as a way to excite higher-order, multipolar plasmons, which would otherwise not be excited by light, as a way to reduce radiation losses. Specifically, electron excited guided plasmons in a coupled nanoparticle chain and a symmetrical four-wire waveguide are separately discussed. In the coupled nanoparticle chain, the plasmon mode formed by quadrupolar polarized particles with low radiation is efficiently coupled by electron beams. Meanwhile, in the four-wire waveguide, the excited plasmons with zero momentum in the cross-section of each wire possess longer propagating distance than other higher-order plasmons. © 2011 Optical Society of America.This work is supported by the Fundamental Research Funds for the Central Universities, the National Natural Science Foundation of China (11004112), the National Basic Research Program of China (2007CB307002, 2010CB934101), the 111 Project (B07013), and the Spanish MICINN (MAT2007-66050 and Consolider NanoLight.es).Peer Reviewe

Light-induced biological waveguides

International audienc

Waveguides of Light through Red Blood Cells

International audienc

Nonlinear optical response and self-trapping of light in biological suspensions

International audienceIn the past decade, the development of artificial materials exhibiting novel optical properties has become a major scientific endeavor. One particularly interesting system is synthetic soft matter, which plays a central role in numerous fields ranging from life sciences, chemistry to condensed matter and biophysics. In this paper, we review briefly the optical force-induced nonlinearities in colloidal suspensions, which can give rise to nonlinear self-trapping of light for enhanced propagation through otherwise highly scattering media such as dielectric and plasmonic nanosuspensions. We then focus on discussing our recent work with respect to nonlinear biological suspensions, including self-trapping of light in colloidal suspensions of marine bacteria and red blood cells, where the nonlinear response is largely attributed to the optical forces acting on the cells. Although it is commonly believed that biological media cannot exhibit high optical nonlinearity, self-focusing of light and formation of soliton-like waveguides in bio-soft matter have been observed. Furthermore, we present preliminary results on biological waveguiding and sensing, and discuss some perspectives towards biomedical applications. The concept may be developed for subsequent studies and techniques in situations when low scattering and deep penetration of light is desired