This PDF file contains the front matter associated with SPIE Proceedings Volume 9278, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.
The emerging field of metasurfaces has offered unprecedented functionalities for shaping wave fronts and optical responses. Here, we realize a new class of metasurfaces with nanorod array, which can generate abrupt interfacial phase changes to control local wave front at subwavelength scale. The physical mechanism under the phase modulation is geometry phase in essence, thus can achieve broadband operation, as well as helicity-dependent property. Multiple applications have been demonstrated, such as anomalous refraction, ultrathin dual-polarity metalenses, helicitydependent unidirectional surface plasmon polariton (SPP) excitation, and three-dimensional (3D) holography.
The quantum-mechanical and thermal phenomena in the plasmonic nanoparticle and resonator are investigated. We develop quantum plasmonics by quantizing the collective electron motion in the surface plasmon. The operator of the electric field inside the metal nanoparticle is found. Thus obtained quantum electric field is anomalous large even for few plasmon quanta. The strong electric field, which value is comparable with the atomic field, results in huge electric current and overheating the metal nanoparticle when it operates as a resonator for the plasmon laser (SPASER). It is shown the overheating thermal instability can explode the particle.
We manipulate the second harmonic generation (SHG) near-field and far-field radiation properties from metasurfaces composed of split ring resonators (SRRs). The manipulation is done by inverting the symmetry of the SRRs in periodic manner. We show by numerical models and experimentally that by that the nonlinear emission can be directed and that the emission direction can be controlled by changing the properties of the arrays or by changing the wavelength of the exciting beam at the first harmonic. This can be used as a new form of all-optical nonlinear scanner based on extremely thin metasurface. These methods open the door for development of new integrated nonlinear active devices based on metasurfaces and can be used to enhance the efficiency of the nonlinear output, therefore it provides a major step forward towards the development of efficient nonlinear metamaterials.
Chiral plasmonic nanostructures offer the ability to achieve strong optical circular dichroism (CD) activity over a broad spectral range, which has been challenging for chiral molecules. Chiral plasmonic nanostructures have been extensively studied based on top-down and bottom-up fabrication techniques. Particularly, in the top-down electron-beam lithography, 3D plasmonic nanostructure fabrication involves layer-by-layer patterning and complex alignment, which is time-consuming and causes many defects in the structures. Here, we present a free-standing 3D chiral plamonic nanostructures using the electron-beam lithography technique with much simplified fabrication processes. The 3D chiral plasmonic nanostructures consist of a free-standing ultrathin silicon nitride membrane with well-aligned L-shape metal nanostructures on one side and disk-shape ones on the other side. The free-standing membrane provides an ultra-smooth metal/dielectric interface and uniformly defines the gap between the upper and lower layers in an array of chiral nanostructures. Such free-standing chiral plasmonic nanostructures exhibit strong CD at optical frequencies, which can be engineered by simply changing the disk size on one side of the membrane. Experimental results are in good agreement with the finite-difference time-domain simulations. Such free-standing chiral plasmonics holds great potential for chirality analysis of biomolecules, drugs, and chemicals.
Treating surface-only nonlinear optical response of graphene as the nonlinear boundary condition in Maxwell equations and applyting perturbation expansion, the pulse propagation equation for graphene plasmonic waveguides is derived. Effective nonlinear coefficient due to the graphene is derived and compared to bulk nonlinear response of dielectrics.
We demonstrate selective coherent perfect absorption based on interaction between bilayered asymmetrically split rings (ASRs) metamaterials and a standing wave formed by two coherent counter propagating beams. The selective coherent perfect absorbers with high absorption have been achieved depending on the phase difference between two coherent beams. The selective coherent control absorbers can be well designed by changing the thickness of the dielectric layer and the asymmetry of the ASRs. The coherently controlled metamaterials provide an opportunity to realize selective multiband absorption and ultrafast information processing.
We propose an infrared biosensor for nanofluidic analysis based on graphene plasmonics, which consists of a nanochannel etching on a silicon substrate and a graphene sheet covered on the top of the channel. The change of refractive index due to the absorption of biomolecules in the nanochannel can be measured by detecting the wavelength shifts of resonant dips. To achieve the best optical performances of the biosensor, an optical model based on finite element method is built to optimize the structure parameters of the biosensor. Numerical simulation results show that a biosensor with a larger top width and a higher depth shows a better overall performance and a high sensitivity value of up to 1920nm/RIU can be achieved in an optimized structure. In addition, the biosensor can dynamically work at a wide range of infrared region by adjusting the Fermi level of graphene. Graphene is pre-coated with poly methyl methacrylate to overcome the effect that the portion of graphene over the nanochannel will be strained and the influence of the thickness of this coated layer on the performances of biosensor is very small. The designed graphene plasmonics devices will advance further applications of graphene in integrated nanofluidic analysis and infrared biosensors.
After discovery of extraordinary transmission (EOT) subwavelength hole arrays structures patterned on a metal film have generated wide interest as they offer high optical transmission and strong localized electric near-field intensities. However, the large ohmic losses exhibited by SPs in the optical regime represent a fundamental limitation that reduces drastically the practical applicability of EOT properties. Furthermore, not compatible with silicon platform make it difficult for application purposes. As a possible solution to this fundamental problem, gain medium have been introduced to compensate the loss created by metallic film. But the most important yet challenging requirements for gain material are to be silicon compatible and working at telecommunication regime. The aim of this paper is to theoretically study optical amplification of EOT properties in periodic hole arrays incorporating optically pumped gain media. The gain media was selected Erbium/Ytterbium(Er/Yb) silicate that is silicon compatible with photoluminescence peak at telecommunication regime. Use of Er3+ ions has the advantages of proven, stable, and low-noise operation at the technologically important 1.54 m region. To excite the active material a laser with a maximum power of 372 mW at the wavelength of 1480 nm is applied. Geometrical parameters was obtained by solving the surface plasmon dispersion relation on periodic hole arrays. The condition for lossless propagation was obtained analytically. Simulation results shows that for lossless propagation we will need higher gain value. By considering higher gain values the absorption was approached to zero 30% transmission enhancements was observed at telecommunication wavelength.
Recently, co-reduction of Au and Pd has allowed the synthesis of complex Au core/AuPd shell nanoparticles with elongated tips and cubic-like symmetry. Optical studies have shown strong plasmonic behavior and high refractive index sensitivities. In this paper, we describe the composition and the near-field plasmonic behavior of those complex structures. Monochromated STEM-EELS, Cathodoluminescence, and EDS mapping reveals the different resonant modes in these particles, and shows that Pd, a poor plasmonic metal, does not prevent strong resonances and could actually be extremely helpful for plasmon-enhanced catalysis.
Silicon nanowire (SiNW) arrays are fabricated by laser interference lithography (LIL) and metal assisted chemical etching. The LIL produces well-ordered surface nanostructures and the following metal assisted chemical etching configures the patterns into high-aspect-ratio three dimensional (3D) nanostructures. The SiNWs exhibit strong antireflection properties. The surface reflection decreases with the height of SiNWs. With Ag thin film coating, such black Si surfaces are applied as surface enhanced Raman scattering (SERS) substrates to measure the 4-methylbenzenethiol molecules adsorbed on the sample surface. The change of SERS signal intensity with the height of SiNWs is investigated. Higher SiNWs exhibit stronger SERS signals due to the large surface area. Meanwhile, Ag nanoparticles (NPs’) decoration on SiNWs via either thermal annealing or redox reaction has been demonstrated for the SERS detection in comparison to Ag film coating. Ag NPs’ decoration by redox reaction greatly improves the SERS signal intensity due to the generation of high density hotspots. However, the thermal annealing method weakens the SERS signals due to oxidation of Ag NPs.
We show the fabrication of plasmonic crystals from 1D to 3D using focused ion beam milling. As typical examples, 1D gratings with uniform profiles, 2D nanoholes/nanorings and 3D nanostructures with complex geometries are demonstrated, respectively. Our approach may find useful applications in plasmon-related nanophotonics and optics.
We present an optically controlled terahertz (THz) switch to tune the state of polarization based on single-layer chiral metamaterial. The chiral metamaterial consists of an array of perforated S-shaped slits with incorporated photoactive silicon, which allows us to control dynamically cross-polarization transmission. The switch state can be efficiently controlled by external optical stimuli. The realization of cross-polarization THz switch in a single-layer metamaterial has simple structure design and easy fabrication and therefore the S-shaped metamaterial will be a promising candidate for polarization control devices.
The unique advantages such as brightness, non-photobleaching, good bio-compatibility make gold nanoparticles desirable labels and play important roles in biotech and related research and applications. Distinguishing gold nanoparticles from other dielectric scattering particles is of more importance, especially in bio-tracing and imaging. The enhancement image results from the localized surface plasmon resonance associated with gold nanopartilces makes themselves distinguishable from other dielectric particles, based on which, we propose a dual-wavelength detection method by employing a high sensitive cross-polarization microscopy.
We propose an ultrathin planar metamaterial with an abrupt phase change along its surface for beam manipulation. The metamaterial is composed of bilayered asymmetrical split ring apertures (ASRAs) on either side of a dielectric substrate. The proposed metamaterial relies on eight variable ASRAs in a super cell to modulate the phase of transmitted wave. Efficient beam direction manipulation for cross-polarization transmission has been achieved and co-polarization transmission has been completely suppressed. Numerical simulation results show that the linearly polarized incident wave can deflect in a designated direction passing through the ultrathin metamaterial. An intensity efficiency of 70% and a deflection angle of 24° at 6.2GHz have been verified.
Absorption properties of film-coupled log-periodic optical antennas in the near-infrared region are numerically investigated. The maximum absorption for TE and TM polarizations at normal incidence reach to 95% and 93%, respectively, and the optimal absorption of around 90% can be simultaneously obtained for both cases. It is shown that the main absorption peak is independent to light polarizations at normal incidence. Moreover, the log-periodic antenna-assisted absorption represents district polarization selectivity at high-order resonances. For oblique incidence, only the incident light of specific wavelengths within a narrow incidence angle can be almost entirely trapped inside the absorber, indicating special direction and wavelength selectivity of the absorber. All these features would lead to potential applications in photovoltaic technology, sensing, etc.