Electro-optical effects of high aspect ratio P3HT nanofibers colloid in polymer micro-fluid cells.

This Letter reports the electro-optical (EO) effect of Poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofibers colloid in a polymer micro-fluidic EO cell. P3HT nanofibers are high aspect ratio semiconducting nanostructures, and can be collectively aligned by an external alternating electric field. Optical transmission modulated by the electric field is a manifestation of the electro-optical effect due to high inner crystallinity of P3HT nanofibers.

Hollow hybrid plasmonic Mach-Zehnder sensor.

A Mach-Zehnder interferometer (MZI)-based liquid refractive index sensor, utilizing a hollow hybrid plasmonic (HP) waveguide as the sensing element, has been investigated, showing large sensitivity to the refractive index changes of the tested liquids, as well as lower propagation loss in comparison to typical plasmonic waveguide-based ones. The sensor is fabricated using conventional silicon-on-insulator (SOI) technology; therefore, it is compatible to other standard SOI devices. The waveguide sensitivity, S, is experimentally demonstrated to be 0.

High-sensitivity liquid refractive-index sensor based on a Mach-Zehnder interferometer with a double-slot hybrid plasmonic waveguide.

A Mach-Zehnder Interferometer (MZI) liquid sensor, employing ultra-compact double-slot hybrid plasmonic (DSHP) waveguide as active sensing arm, is developed. Numerical results show that extremely large optical confinement factor of the tested analytes (as high as 88%) can be obtained by DSHP waveguide with optimized geometrical parameters, which is larger than both, conventional SOI waveguides and plasmonic slot waveguides with same widths. As for MZI sensor with 40μm long DSHP active sensing area, the sensitivity can reach as high value as 1061nm/RIU (refractive index unit).

Whispering gallery mode nanodisk resonator based on layered metal-dielectric waveguide.

This paper proposes a layered metal-dielectric waveguide consisting of a stack of alternating metal and dielectric films which enables an ultracompact mode confinement. The properties of whispering gallery modes supported by disk resonators based on such waveguides are investigated for achieving a large Purcell factor. We show that by stacking three layers of 10 nm thick silver with two layers of 50 nm dielectric layers (of refractive index n) in sequence, the disk radius can be as small as 61 nm ∼λ(0)/(7n) and the mode volume is only 0.

Design and analysis of ultra-compact EO polymer modulators based on hybrid plasmonic microring resonators.

Ultra-compact EO polymer modulators based on hybrid plasmonic microring resonators are proposed, simulated and analyzed. Comparing with Si slot microring modulator, hybrid plasmonic microring modulator shows about 6-times enhancement of the figure of merit when the bending radius is around 510 nm, due to its much larger intrinsic quality factor in sub-micron radius range. Influences of the EO polymer height and Si height on the device's performance are analyzed and optimal design is given.

Silicon hybrid plasmonic submicron-donut resonator with pure dielectric access waveguides.

Characteristic analyses are given for a bent silicon hybrid plasmonic waveguide, which has the ability of submicron bending (e.g., R = 500 nm) even when operating at the infrared wavelength range (1.

Gain enhancement in a hybrid plasmonic nano-waveguide with a low-index or high-index gain medium.

A theoretical investigation of a nano-scale hybrid plasmonic waveguide with a low-index as well as high-index gain medium is presented. The present hybrid plasmonic waveguide structure consists of a Si substrate, a buffer layer, a high-index dielectric rib, a low-index cladding, a low-index nano-slot, and an inverted metal rib. Due to the field enhancement in the nano-slot region, a gain enhancement is observed, i.

Theoretical study of nanophotonic directional couplers comprising near-field-coupled metal nanoparticles.

The properties of integrated-photonics directional couplers composed of near-field-coupled arrays of metal nanoparticles are analyzed theoretically. It is found that it is possible to generate very compact, submicron length, high field-confinement and functionality devices with very low switch energies. The analysis is carried out for a hypothetical lossless silver to demonstrate the potential of this type of circuits for applications in telecom and interconnects.

Layered metal-dielectric waveguide: subwavelength guidance, leveraged modulation sensitivity in mode index, and reversed mode ordering.

We describe a layered metal-dielectric waveguide, whose fundamental mode has an effective index as high as 7.35 at 1.55 μm, enabling subwavelength spatial confinement.

Sub-μm2 power splitters by using silicon hybrid plasmonic waveguides.

Nano-scale power splitters based on Si hybrid plasmonic waveguides are designed by utilizing the multimode interference (MMI) effect as well as Y-branch structure. A three-dimensional finite-difference time-domain method is used for simulating the light propagation and optimizing the structural parameters. The designed 1 × 2 50:50 MMI power splitter has a nano-scale size of only 650 nm × 530 nm.

Lower bound of energy dissipation in optical excitation transfer via optical near-field interactions.

We theoretically analyzed the lower bound of energy dissipation required for optical excitation transfer from smaller quantum dots to larger ones via optical near-field interactions. The coherent interaction between two quantum dots via optical near-fields results in unidirectional excitation transfer by an energy dissipation process occurring in the larger dot. We investigated the lower bound of this energy dissipation, or the intersublevel energy difference at the larger dot, when the excitation appearing in the larger dot originated from the excitation transfer via optical near-field interactions.

Optical magnetic plasma in artificial flowers.

We report the design of an artificial flower-like structure that supports a magnetic plasma in the optical domain. The structure is composed of alternating "petals" of conventional dielectrics (epsilon > 0) and plasmonic materials (Re(epsilon ) < 0). The induced effective magnetic current on such a structure possesses a phase lag with respect to the incident TE-mode magnetic field, similar to the phase lag between the induced electric current and the incident TM-mode electric field on a metal wire.

Experimental demonstration of a cross-order echelle grating triplexer based on an amorphous silicon nanowire platform.

We present the design, fabrication, and characterization of an ultracompact silicon-on-insulator-based echelle grating triplexer. It is based on the cross-order design, which utilizes different diffraction orders to cover a large spectral range from 1.3 to 1.

Feasibility study of nanoscaled optical waveguide based on near-resonant surface plasmon polariton.

Currently subwavelength surface plasmon polariton (SPP) waveguides under intensive theoretical and experimental studies are mostly based on the geometrical singularity property of such waveguides. Typical examples include the metal-insulator-metal based waveguide and the metallic fiber. Both types of waveguides support a mode with divergent propagation constant as the waveguides' geometry (metal gap distance or fiber radius) shrinks to zero.

A lossless negative dielectric constant from quantum dot exciton polaritons.

Prospects for a lossless negative dielectric constant material for optical devices are studied. Simulations show that with sufficient gain, a mixture of two semiconductor quantum dots (QDs) can produce an effective dielectric constant that is lossless and negative. This permits, in concept, arbitrarily small scaling of the optical mode volume, a major goal in the field of nanophotonics.

Perfect-lens-material condition from adjacent absorptive and gain resonances.

We suggest, based on the principle of causality and for a material exhibiting adjacent absorptive and gain resonances, that there can be an intervening frequency where perfect imaging is in theory possible. At this frequency, both the dielectric constant and the permeability are negative, leading to a negative refractive index, and there is no loss. In such a material exhibiting a double resonance, the gain must be at the higher frequency.

Study of an ultrafast analog-to-digital conversion scheme based on diffractive optics.

A potentially ultrafast optical analog-to-digital (A/D) converter scheme is proposed and was partly studied experimentally. In the A/D converter scheme the input signal controls the wavelength of a diode laser, whose output beam is incident on a grating. The beam from the grating hits a diffractive optical element in an array.

Photonic crystals--a step towards integrated circuits for photonics.

The field of photonic crystals has, over the past few years, received dramatically increased attention. Photonic crystals are artificially engineered structures that exhibit a periodic variation in one, two, or three dimensions of the dielectric constant, with a period of the order of the pertinent light wavelength. Such structures in three dimensions should exhibit properties similar to solid-state electronic crystals, such as bandgaps, in other words wavelength regions where light cannot propagate in any direction.

Negative refraction at infrared wavelengths in a two-dimensional photonic crystal.

We report on the first experimental evidence of negative refraction at telecommunication wavelengths by a two-dimensional photonic crystal field. Samples were fabricated by chemically assisted ion beam etching in the InP-based low-index constrast system. Experiments of beam imaging and light collection show light focusing by the photonic crystal field.

Analysis of a directional coupler by coupled modes of a single waveguide.

Analysis of a directional coupler by use of rigorous coupled-mode theory is presented. The coupling process is explained by the mutual coupling of modes of a single waveguide that is due to the presence of the other waveguide. It is explicitly shown by example that the radiation modes that take part in the coupling are just those needed to form the guided modes of the composite double-guide structure.

Beam-propagation method analysis of a nonlinear directional coupler.

The beam-propagation method is employed to analyze nonlinear directional-coupler operation for various combinations nonlinear materials and initially mismatched guides. A mixed focusing-defocusing configuration is found optimal results.

Beam propagation method in anisotropic media.

An extension of the beam propagation method to anisotropic media is presented and the formalism is employed to study several integrated optics devices.

Electrooptic integrated optics spectrum analyzer: an experimental investigation.

An integrated optics spectrum analyzer based on using the linear electrooptic effect was theoretically investigated earlier. This spectrum analyzer performs Fourier analysis of sampled electronic signals, where each voltage sample is fed to an electrode of a metal electrode array. The electrode array acts as a spatial light modulator, and the diffracted light field is focused on a detector array.

Electrooptic approach to an integrated optics spectrum analyzer.

An integrated optics spectrum analyzer based on using the linear electrooptic effect is investigated. This spectrum analyzer performs Fourier analysis of sampled electronic signals, where each signal is fed to an electrode of an electrode array. The electrode array acts as a spatial light modulator, and the diffracted light field, representing a weighted discrete Fourier transform (DFT), is focused on a detector array by an integrated transform lens.