This PDF file contains the front matter associated with SPIE Proceedings Volume 10824 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

We have introduced a novel plasmonics planar slit lens, consisting of five slits with gradually decreasing widths and interspace distances. The cascading constant k to correlate the geometrical parameters with each other is proposed. At specific k values, light propagating through the slits is amplified and shows extraordinary transmission and focusing features beneath the metallic layer that we name it as the cascading effect. The focusing is due to the additional phase imposed on traveling light through the slits and their constructive interference. Numerical simulation Results show that the slit width should not be larger than half wavelength, and the cascading constant should be between 0.3 and 0.4.

Localized surface plasmon based on coupled metallic nanoaggregates has been extensively studied in enhancing light scattering and optical force, which depends on the geometry/symmetry of plasmonic oligomers and the refractive index of surrounding medium. As the interparticle gap distance between nanoparticles becomes smaller than several nanometers, quantum effects can change the plasmon coupling in classical predictions. However, most of the research on plasmonic scattering and optical force has been done based on local calculations even for the gap below ~3 nm, in which the nonlocal screening plays a vital role. Here, we theoretically investigate the nonlocal effect on the evolution of plasmon resonance modes in strongly coupled nanoparticle dimer antennas with the gap down to 1 nm. Then, the refractive index sensing and optical force in this nonlocal system is evaluated and compared with the results in classical calculations. We find that in the nonlocal regime, both refractive index sensibility factor and optical force are actually smaller than their classical counterparts mainly due to the saturation of both plasmon-shifts and near-field enhancement. These results would be beneficial for the understanding of interaction between light and nonlocal plasmonic nanostructures and the development of plasmonic devices such as nanoantennas, nanosensors, and photonic manipulation.

Here we will mainly investigate the coupling mechanism of bilayered optical metamaterials with a standing wave and the selective coherent perfect absorption in bilayered optical metamaterials by the two coherent beams. The metamaterials consist of bilayered asymmetrically split rings (ASR) with different twist angles 0° and 180°, spatially separated by a very thin dielectric substrate. Electric and magnetic dipolar excitations can be selectively enhanced or eliminated when the ASR is placed at the antinode and the node of the standing waves, meaning that the phase difference of the signal and control beams is 0° and 180‡°. The simulated results show that coherent perfect absorption can be realized at different frequencies and in particular each one can be switched on/off depending on the phase difference between the signal and control beams. In comparison with 35% absorption in the single-layer ASR metamaterial, the coherent perfect absorption occurs with larger than 95% absorption. In summary, we realize an ultra-thin subwavelength coherent absorber that holds much more flexibility operating at any frequency ranging from microwave to optical regimes. The response of metamaterials can be coherently tailored by easily changing their positions in the standing wave.

Hybrid nanostructures, comprising of a metal core and a semiconductor shell layer, shows great potential for a new generation of low-cost solar cells, due to their unique electronic and optical properties. However, experimental results have fallen far short of unltra-high efficiency (i.e. beyond Shockley-Queisser limit) predicted by theoretical simulation, limiting commercial application. Here, we experimentally design a non-transparent organic solar cell containing an array of Ag/ZnO nanowires, increasing internal quantum efficiency (IQE) by a factor of 2.5 compared with the planar counterpart, indicating a great enhancement of charge collection efficiency, due to the ultrafast Ag nanowire channels. Furthermore, we exploit this hybrid nanostructure as a perfect back reflector for semi-transparent solar cells, resulting in enhanced light absorption by a factor of 1.8 compared with the planar counterparts. The ability to enhance the charge collection and light absorption makes these Ag/ZnO nanostructures a flexible platform for the development of modern optoelectronic devices.

Optical Tamm plasmon (TP) can be excited at the boundary of photonic crystal and metal film. In this work, we propose a composite structure consisting of binary Au nanodisk arrays on the top of a distributed Bragg reflector (DBR) with 19.5 pair TiO₂/SiO₂ 1D photonic crystal. The designed structure has strong confined mode at the boundary of DBR near to the binary Au nanodisk arrays, and the bandwidth of reflection spectrum is broadened obviously compared with that of the structure of Au film on the top of DBR. The conventional TP state at the boundary of nanodisks and DBR structure are modified while decreasing the size and period of binary Au nanodisk resulting from the collective lattice resonances supported by Au nanodisk. Two TP modes at 1100 nm and 1164 nm wavelength are found in reflection spectrum corresponding to different particle radii with 120 nm and 100 nm, and as the magnitude of particle radii in the two arrays approaches gradually, only one TP mode is found, which demonstrate the in-phase and anti-phase lattice resonances in different particle radii modified the confined field distribution of Tamm state at the boundary between Au nanodisk and DBR structure, generating a hybrid mode of TP and lattice resonance based on surface plasmon resonance. Coupling of TP mode and localized lattice resonance mode leads to the appearance of dual Tamm states with only one kind period DBR structure controlled by the radii of binary Au nanodisk array.

Surface enhanced Raman spectroscopy (SERS) is capable of sensing not only the chemical nature but also the biological organisms. In this work, it is experimentally demonstrated that silver and reduced graphene oxide nano-composite based material can be used as SERS platform. Localized surface plasmon resonance (LSPR) property of silver nanostructure such as nano-sphere, nano-dendrites and nano-prism and high impermeability of reduced graphene oxide (RGO) have been employed to build a composite for SERS measurements. Graphene oxide was synthesized using Hummer’s Method and then simple facile method was used for its reduction as well as for the deposition of silver nanostructure on it. SEM, XRD, FTIR, and UV-Vis techniques characterized the prepared nano-composite of Ag-RGO. The composite material was used for SERS measurement for the detection of Escherichia Coli (E. Coli) bacteria at a concentration of 8×10⁶ CFU/ ml and it is observed that signal of silver nanodentries-RGO composite was intense in comparison with Ag-RGO nano-sphere and nano-triangular composite.

The high cost associated with the traditional plasmonic materials and the complex nanofabrication has hindered their practical applications and therefore alternative plasmonic materials and nanofabrication techniques are needed. Here, I combined cost-effective colloidal lithography and earth-abundant element, i.e. Al, to fabricate Al optical nanoantennas including Al nanotriangles and Al metamaterial perfect absorbers. I demonstrate surface functionalization of the nanoantennas using phosphonic acid and subsequent detection of the C=O vibration mode via surface-enhanced infrared absorption spectroscopy. In addition, the detection of a physically adsorbed thin polymer layer on the Al nanoantennas is demonstrated. Surface functionalization with phosphonic acid provides various functional groups to the Al surfaces opening up great opportunities for Al-based plasmonic nanostructures for biochemical sensing applications.

The research of the fabrication of plasmonic nanowire waveguides and circuits for nanophotonic circuitry applications by lithographic fabrication method has attracted much attention. Here we report an approach for fabricating metal nanowire networks by electron beam lithography and metal film deposition techniques. The gold nanowire structures without adhesion layer are fabricated on quartz substrates and a thin layer of Al₂O₃ film is deposited using atom layer deposition for immobilizing the nanostructures. During the Al₂O₃ deposition process, the thermal annealing effect can decrease the surface plasmon loss on the nanowires. Y-shaped gold nanowire networks are fabricated and the surface plasmons can be routed to different branches by controlling the length of the main nanowire and the polarization of the excitation light. The simulation results of the electric field distributions show that the zigzag distribution of electric field on the main wire determines the surface plasmon routing. The interference of surface plasmons in the nanowire network can modulate the output intensity to realize Boolean logic operations. AND, OR, XOR and NOT gates are realized in three-terminal nanowire networks, and NAND, NOR and XNOR gates are realized in four-terminal nanowire networks. This work provides a new way for on-chip integrated plasmonic circuits.

The hybrid systems of multiple quantum emitters coupled with plasmonic waveguides provide promising building blocks for the future integrated quantum nanophotonic circuits. The techniques that can selectively excite adjacent quantum emitters in a diffraction-limited area are of great importance for studying the plasmon-mediated interaction between quantum emitters and manipulating the generation and propagation of single plasmons in nanophotonic circuits. We show that by modulating the electric field on the nanowire using the interference of surface plasmons, multiple quantum dots coupled with a silver nanowire can be controllably excited. We experimentally demonstrate the selective excitation of two quantum dots with a separation distance of about 100 nm. Our work provides a new kind of optical excitation and characterization method overcoming the diffraction limit, and adds a new tool for studying and manipulating single quantum emitters and single plasmons for quantum plasmonic circuitry applications.

In this work, a metamaterial with 90°-twisted nanorods is presented and numerically investigated. Numerical simulated results demonstrate that our scheme can realize strong chiroptical response of the metamaterial to circularly polarized waves. We investigate circular dichroism in a bilayer chiral metamaterial in the optical range. The circular dichroism is very strong up to 75%. We also consider how the incident angle of the circular polarized wave affects the circular dichroism. We can achieve strong circular dichroism by changing the incident angle. The proposed metamaterial will be a good candidate for biosensing applications.

Light emission from single gold nanorods excited by continuous wave lasers was investigated by using ultra-narrow-band notch filters to obtain their complete spectral shape. The spectral profile of Stokes emission can be fitted by a Lorentzian line shape and that is dominated by localized surface plasmon resonance. Moreover, a clear anti-Stokes emission band can be always observed under different excitation wavelengths. The spectral shape of anti-Stokes emission can be fitted well with a Fermi-Dirac like line shape. Electron Fermi-Dirac distribution should influence the spectral shape of anti-Stokes emission for both interband and intraband transitions. It was also found that the intensity of anti-Stokes emission increases more rapidly in comparison with that of Stokes emission as illumination power increases on resonant excitation. This phenomenon can be understood as the temperature dependent of the electron Fermi-Dirac distribution due to photothermal effect.

In the surface-enhanced fluorescence (SEF) process, it is well known that the plasmonic nanostructure can enhance the light emission of fluorescent emitters. With the help of atomic force microscopy, a hybrid system consisting of a fluorescent nanodiamond and a gold nanoparticle was assembled step-by-step for in situ optical measurements. We demonstrate that fluorescent emitters can also enhance the light emission from gold nanoparticles which is judged through the intrinsic anti-Stokes emission owing to the nanostructures. The light emission intensity, spectral shape, and lifetime of the hybrid system were dependent on the coupling configuration. The interaction between gold nanoparticles and fluorescent emitter was modelled based on the concept of a quantised optical cavity by considering the nanodiamond and the nanoparticle as a two-level energy system and a nanoresonator, respectively. The theoretical calculations reveal that the dielectric antenna effect can enhance the local field felt by the nanoparticle, which contributes more to the light emission enhancement of the nanoparticles rather than the plasmonic coupling effect. The findings reveal that the SEF is a mutually enhancing process. This suggests the hybrid system should be considered as an entity to analyse and optimise surface-enhanced spectroscopy.

As the basic geometric structure unit for generating surface plasmon, the split ring and the disk have been researched widely in both theory and experiment. A split asymmetric ring-disk (SAR-D) nanostructure is proposed to achieve both magnetic double Fano resonances and near field enhancement, which is investigated numerically based on the finite element method. In this nanostructure, Fano resonance is produced by the destructive interference between the bright electric mode and the dark magnetic mode. The extinction spectra can be modulated by changing the distance between the split asymmetric ring (SAR) and the disk, the thickness of the nanostructure and the radii of the SAR or the disk. Magnetic double Fano resonances can be excited effectively by rotation the SAR-D structure or splitting the disk along y-axis. Calculation results show that near field intensity is enhanced greatly at resonance peaks. Splitting the disk along y-axis, the strongest electric and magnetic field enhancements are achieved at the split gap, which are 386 and 118, respectively. This SAR-D nanostructure have potential applications in the surface enhance plasmon spectroscopy, the propagation of low-loss magnetic plasmons and the multiwavelength spectrometer.

In this work, two split U-shaped metamaterials with photoconductive silicon layer are presented and numerically investigated. The electromagnetically induced transparency can be manipulated by changing angles of the incident wave and the conductivity of silicon. At oblique incidence of 50°, the metamaterials exhibit an obvious photoswitching effect. The transmittance peaks of both two structures are as high as about 0.7, respectively. The fishscale metamaterials with integrated silicon layer show a very high modulation depth. Based on the modulation of the conductivity of the silicon, the scheme can be readily applied to realize THz metamaterial switch.

A reflective color filter based on the standing-wave resonance is proposed, incorporating an asymmetric cross-shaped aluminum grating on top, a sandwiched silicon nitride layer and an aluminum mirror at bottom. By varying the length of grating arms or the polarization of incident lights, reflective colors as cyan, magenta and yellow can be obtained conveniently. Specially, reflections show good angular tolerance up to 60° for transverse electric polarization, while they demonstrate high sensitivity to incident angles of transverse magnetic polarization. Furthermore, the black color can be realized in reflection by encoding four gratings into one pixel at the optical diffraction limit. The color filter proposed here has great potential in applications as reflective LCD, full color printing and anti-counterfeiting.