Spin-Direction-Spin Coupling of Quasiguided Modes in Plasmonic Crystals.

We report an unusual spin-direction-spin coupling phenomenon of light using the leaky quasiguided modes of a waveguided plasmonic crystal. This is demonstrated as simultaneous input spin-dependent directional guiding of waves (spin-direction coupling) and wave-vector-dependent spin acquisition (direction-spin coupling) of the scattered light. These effects, manifested as the forward and the inverse spin Hall effect of light in the far field, and other accompanying spin-orbit interaction effects are observed and analyzed using a momentum (k) domain polarization Mueller matrix. Resonance-enabled enhancement of these effects is also demonstrated by utilizing the spectral Fano resonance of the hybridized modes. The fundamental origin and the unconventional manifestation of the spin-direction-spin coupling phenomenon from a relatively simple system, ability to probe and interpret the resulting spin-orbit phenomena in the far field through momentum-domain polarization analysis, and their regulated control in plasmonic-photonic crystals open up exciting avenues in spin-orbit-photonic research.

Stable hybrid plasmonic directional coupler based on an embedded silver nanostructure waveguide.

In this paper, a stable hybrid plasmonic optical directional coupler based on an embedded silver nanostructure that can offer a power transfer up to 95% is presented. This optimum power transfer is obtained at an outer edge-to-edge separation of 0.58 µm between the two waveguides. The obtained propagation loss is as low as 0.0863 dB/µm. The electric field distributions of the symmetric and antisymmetric modes of the coupler are compared, and the transmission characteristics are studied in detail using the finite element method. The performances of the directional coupler have been further characterized in terms of excess loss, coupling degree, and directionality. The shortest coupling length at which the maximum power coupling occurs is obtained as 2.488 µm. The proposed compact directional coupler features good field confinement and low propagation loss, which opens the door for many device applications in photonic-integrated circuits and optoelectronic industries.

Natural weak value amplification in Fano resonance and giant Faraday rotation in magneto-plasmonic crystal.

The extraordinary concept of weak value amplification can be formulated within the realm of wave interference as nearly destructive interference between the eigenstates of the measuring observable. Here we report on a phenomenon of interferometric weak value amplification of small polarization rotation in Fano resonance that evolves completely naturally due to near destructive spectral domain interference between a continuum and a narrow resonance mode having slightly different polarization response. In order to elucidate this, we first experimentally demonstrate an interferometric weak value amplification concept by generating nearly destructive interference of two paths of an interferometer having slightly rotated linear polarization states of light. The weak value amplification of polarization rotation effect is manifested as dramatic changes in the polarization state of light, which acts as the pointer. We go on to demonstrate that the manifestation of natural interferometric weak value amplification is an important contributing factor to the observed giant Faraday rotation and ellipticity in waveguided magneto-plasmonic crystals exhibiting prominent Fano resonance. The natural weak value interpretation of the enhanced Faraday rotation in hybrid magneto-plasmonic systems enriches the existing understanding on its origin. This opens up a new paradigm of natural weak measurement for gaining fundamental insights and ensuing practical applications on various weak interaction effects in rich variety of wave phenomena that originate from fine interference effects.

Numerical simulation on the performance analysis of a graphene-coated optical fiber plasmonic sensor at anti-crossing.

A graphene-based surface plasmon resonance sensor using D-shaped fiber in anti-crossing has been designed. Silver as a plasmon active metal is followed by graphene, which helps in preventing oxidation and shows better adsorption efficiency to biomolecules. A wavelength interrogation technique based on the finite element method has been used to evaluate performance parameters. Design parameters such as thickness of silver, residual cladding, and GeO2 dopant concentration have been optimized. The wavelength sensitivity is found to be 6800 nm/RIU and resolution of 8.05×10-5 RIU. We believe that usage of graphene on silver may open a new window for study of online biomolecular interaction.