Koray Aydin, Northwestern University
Stefan Maier, Imperial College London
Robert Walters, Integrated Plasmonics Corporation
Rashid Zia, Brown University
Symposium Support Nature Photonics
NKT Photonics Inc.
Tuesday PM, April 22, 2014
Moscone West, Level 3, Room 3006
2:30 AM - *II2.01
Substrate Conformal Imprint Lithography in Nanophotonic Applications
Marc A. Verschuuren 1 Jamie Rivas 2
1Philips Research Eindhoven Netherlands2Van der Waals-Zeeman Inst Amsterdam NetherlandsShow Abstract
Nanoimprint lithography (NIL) is seen as a promising technology for the cost effective fabrication of sub-micron and nano-patterns on large areas. Real world conditions such as substrate bow and particle contaminants rule out the use of hard/rigid stamps over wafer scale areas. Hence soft- rubber-like stamp are required. Substrate Conformal Imprint Lithography (SCIL), a full wafer scale NIL technique will be introduced. SCIL combines the low cost, flexibility and robustness of PDMS rubber working stamps, with the nm resolution and low pattern deformation of small rigid stamps. This allows us to research large area photonic and plasmonic applications with a route towards industrialization. We will demonstrate that large area nano-pattens can deliver enhanced performance for LEDs, lasers, thin film - and wafer based photo-voltaics.
White light LEDs use a phosphor layer to partly convert blue light from the LED chip. We demonstrate a very large improvement in phosphor emission (60-fold directional enhancement for unpolarized emission) using nanophotonic structures. This is attained by coupling emitters with high (80%) quantum efficiencies to collective plasmonic resonances in large area periodic arrays of aluminum nanoantennas.
Vertical cavity surface emitting lasers or VCSELs are a type of low cost laser manufactured in high volume and used in fiber optic data communications, optical tracking and sensing applications. Due to the planar technology the VCSELs polarization direction can flip. To lock the polarization a grating is applied on one of the laser mirrors. We imprint gratings on 3” GaAs wafers which contain the final laser stack, etch the semiconductor and process into VCSELs. By replacing traditional e-beam patterning with SCIL we improve performance and yield as it enables using a smaller grating pitch, which reduces optical losses and simultaneously lower cost.
The trend in photovoltaics in towards high efficiency cells. We used two approaches to increase light absorption and improve efficiency. First plasmonic back reflectors for thin-film amorphous hydrogenated silicon (a-Si:H). A single imprint on a glass substrate replicates regular and random pillar arrays on which the cell was grown. The plasmonic cell traps light in an only 90nm thick intrinsic a-Si:H layer and reaches an efficiency of 9.6% under AM 1.5 illumination (400nm pitch).
To reduce the reflectivity of single crystal Si wafers we used front side resonant Mie scatterers. These sub-wavelength cylinders trap light over a broad wavelength range and scatter the light preferentially in the high index silicon. The solar spectrum weighted reflection over 450-900nm is reduced to only 1.3%, compared to 3.4% for a standard textured solar cell. Importantly, this approach is applicable to any high index material and is compatible with very thin wafer concepts where traditional AR approaches fail due to the required feature height.
3:00 AM - II2.02
Nano-Imprinted Colloidal Metal Organic Frameworks-Based Diffraction Gratings for Selective Sensing Applications
Faustini Marco 1 Cattoni Andrea 2
1Universitamp;#233; Pierre Marie Curie / College de France Paris France2Laboratoire de Photonique et de Nanostructures Marcoussis FranceShow Abstract
We describe, for the first time, a strategy based on soft-nanoimprinting lithography for the fabrication of colloidal Metal Organic Frameworks (MOF) nanopatterns with periodicity as small as 400 nm and their utilization for sensing applications.
Despite the fact that this new family of hybrid, porous, crystalline materials have attracted immense attention because of their unique physicochemical properties (1) just a few reports demonstrated their patterning at micrometric scale (2); the nanopatterning of MOFs, that would allow their integration into nanophotonic devices, still remains a challenge.
We developed a technique consisting in the direct nanoimprinting from a colloidal solution of preformed nanoparticles of ZIF-8 material, having size ranging from 35 and 50 nm. The nanoparticle were synthetized by simple precipitation of zinc nitrate and imidazole linker and dispersed in ethanol. At first, when the PDMS stamp was applied on a colloidal solution droplet the patterned nanocavities were naturally filled by capillarity. Then, the evaporation of the solvent through the PDMS stamp lead to the replication of the features and to the homogeneous packing of the colloidal network. Several features (squared, linear,..) with nanoscale resolution were demonstrated over large surface up to 1 cm2. This technique does not need any embossing machine and the ZIF-8 nanostructures could be replicated on both rigid and flexible transparent substrates since no pressure was applied to the stamp. The embossed structures were characterized by electronic microscopy while the crystallinity of the material was investigated by GI-WAXS.
Since porous ZIF-8 showed excellent selectivity in vapor adsorption (3) a simple optical sensing device for organic solvents and based on nano-imprinted diffraction gratings was developed. The replicated ZIF-8 system consisted in array of lines with periodicity equal to 400 nm. Due to the relevant change in ZIF-8 refractive index when exposed to organic solvent vapors (from 1,2 to around 1,45 at 700 nm), a sensitive increase in color intensity of the diffracted light could be observed. The easy-detection system was based on the evaluation of the color intensity change that could be probed by a simple camera (or even a smart-phone) without need of complex optical measurements. The -sorption properties of the system exposed to organic and water/organic solvent mixtures were compared with in-situ environmental ellipsometric investigations.
1. N. Stock et al, Chem. Reviews, 112, 933 (2012)
2. P. Falcaro et al, Adv. Mater. 24, 3153-6 (2012)
3. A. Demessence et al, J. Mater. Chem. 20, 36 (2010)
3:15 AM - II2.03
Light Trapping Structures Fabricated by Low Cost and Scalable Techniques
Barbara Brudieu 1 2 Jamp;#233;ramp;#233;mie Teisseire 2 Franamp;#231;ois Guillemot 3 Arthur Le Bris 4 Gamp;#233;raldine Dantelle 1 Fabien Sorin 4 Thierry Gacoin 1
1Ecole Polytechnique Palaiseau France2Saint-Gobain Recherche Aubervilliers France3Saint-Gobain Recherche Aubervilliers France4Ecole Polytechnique Famp;#233;damp;#233;rale de Lausanne Lausanne SwitzerlandShow Abstract
Light management schemes have known a steady development in the past decade as a solution envisioned to enhance the performance of optical and optoelectronic systems. However, to avoid additional processing costs, it is important to propose simple and scalable fabrication techniques to integrate such schemes within functional devices. In this project, we demonstrate highly efficient and tunable light trapping structures prepared using simple and scalable Sol-Gel chemistry, spin coating processing, and Nanoimprint lithography techniques. First, Distributed Bragg Mirrors in the form of periodic dielectric stacks are fabricated with dense TiO2 layers as the high index material (2.08 in the visible range), and macroporous silica layers as the low index counterpart (1.24 with 50% of porosity). In our approach, a single high temperature annealing step is used to create the porosity in the full stack, highlighting its simplicity and potential for industrial deployment. A defect-free semi-transparent 9-layer stack is obtained and shows a high specular reflectivity up to 96% at normal incidence in its prescribed bandwidth. We also demonstrate the flexibility of our process by making highly reflective DBRs with a tunable reflection range from UV to IR (from 400nm to 1300nm). To demonstrate the versatility of our approach, we optimized a 8-layer DBR and integrated it within in a a-Si:H thin-film solar cell, which resulted in an increase of efficiency by 14.6%. More over, we demonstrated an enhancement of the light emission from an Europium-doped luminescent silica layer that is deposited on a Bragg reflector. Finally we will present our latest results on the possibilities opened by the integration of diffraction gratings fabricated by soft Nanoimprint Lithography, with our DBR structures.
3:30 AM - II2.04
Surface Plasmon Resonance in Elastomeric Metal-Polymer Nanocomposites Fabricated by Supersonic Cluster Beam Implantation
Cristian Ghisleri 1 2 Luca Ravagnan 1 Marco Potenza 2 Paolo Milani 1 2
1W.I.S.E. srl Milano Italy2Universitamp;#224; degli Studi di Milano Milano ItalyShow Abstract
The integration of optical elements on elastomeric substrates can pave the way to the realization of a novel class of stretchable photonic systems with the ability of changing their optical properties upon modification of their shape due to tensile or compressive strain and to be highly conformable to complex surfaces [1, 2].
Here we present an effective approach to the fabrication of nanocomposite-based deformable and stretchable optical, photonic systems by means of Supersonic Cluster Beam Implantation (SCBI) of metal nanoparticles in PDMS . A beam of electrically neutral nanoparticles, accelerated by a pressure difference and focused with a very low divergence by aerodynamical effects, is directed towards the polymeric substrate and gain sufficient kinetic energy to get implanted. The extremely good resilience of the nanoparticles layer embedded in the polymer upon deformation of the so obtained nanocomposite allows to maintain extremely good optical performances upon substantial deformation of the material and a large number of deformation cycles . Moreover the low energies involved in the SCBI implantation process avoid the deterioration of the physical and chemical (and thus the dielectric) properties of the PDMS substrate [3-5].
SCBI metal polymer nanocomposites exhibit interesting plasmonic properties, because of the nanoparticles dynamics inside the PDMS matrix, and represent an extremely useful tool for the understanding and control the macroscopic opto-electronic properties of nanocomposite-based devices. Surface plasmon resonance (SPR) of Ag/PDMS and Au/PDMS nanocomposites with a continuous gradient of implanted nanoparticles doses and thermal annealing treatments is well described by Maxwell Garnett and Shell-Core models. This helps in improving the high tunability and control the optical response of the material by playing on the implantation process parameters and post-implantation treatments.
Moreover, preliminary results of the SPR behavior of the nanocomposite under stretching show a high sensitivity of the SPR response to deformations, suggesting the exploitation of plasmonic nanocomposites for sensing applications.
 C. Ghisleri et al., Laser & Photon. Rev. 7, 1020 (2013)
 J.L. Wilbur et al., Chem. Mater. 8, 1380-1385 (1996)
 C. Ghisleri et al., Accepted by J. Phys. D (2013)
 R. Cardia et al., J. Appl. Phys. 113, 224307 (2013)
 G.Corbelli et al., Adv. Mater. 23, 4504 (2011)
3:45 AM - II2.05
M13 Virus Based SERS Nanoprobe for Quantitative Detection of Antigen
Hye-Eun Lee 1 Hwa Kyoung Lee 2 Hyejin Chang 3 Hyo-Yong Ahn 1 Norov Erdene 3 Ho-Young Lee 4 Yoon-Sik Lee 5 Dae Hong Jeong 3 Junho Chung 2 Ki Tae Nam 1
1Seoul National University Seoul Republic of Korea2Seoul National University College of Medicine Seoul Republic of Korea3Seoul National University Seoul Republic of Korea4Seoul National University Bundang Hospital Seoul Republic of Korea5Seoul National University Seoul Republic of KoreaShow Abstract
Surface-enhanced Raman scattering (SERS) nanoprobe consisted by metallic nanostructure and capturing antibody offers unprecedented opportunity for ultrasensitive detection of antigen due to its strong signal generation arising from metallic nanostructure. Though many strategies have been developed that can precisely control metallic nanostructure for uniform SERS signal generation, most of antibody conjugation process are still relied on the conventional methods which lack controllability of antibody orientation and also conjugating various kinds of antibody remains as challenging work. Here, we demonstrate a new M13 virus based SERS nanoprobe (viral probe) that has strong SERS signal and possesses single antibody with controlled orientation enabling quantitative immunoassay. M13 virus is composed of 5 different proteins (p3, p6, p7, p8, and p9) with filamentous shape. Each protein can be easily modified via genetic engineering of M13 genome and this enables rational design of virus for SERS nanoprobe. The long p8 part was served as a template for assembling gold nanoparticles thereby generating SERS signal. By expressing gold nanoparticle binding sequence on p8, gold nanoparticles could be assembled closely along the virus. For antigen detection, an antibody was expressed on p3 protein. As the antibody can be expressed with orientation, the epitope can be fully exposed providing excel antigen capturing ability. Additionally, since all the viruses have the same capturing ability, exploiting this virus is desirable to quantitative immunoassay. Also, p3 part has been utilized for discovering antibody by constructing various antibodies on p3. Therefore, such easy expression of antibody on p3 facilitates fabrication of numerous types of SERS nanoprobe that capture diverse antigen. The formation of assembled gold nanoparticle on the virus was confirmed by UV-vis spectroscope, scanning electron microscope, and dark field microscope and these results clearly showed the aligned multiple nanoparticles along the virus. The SERS activity of fabricated viral probe was evaluated by Raman measurement on each probe. Strong and uniform SERS signal was generated from the viral probe originating from the assembled nanoparticles. We demonstrated the validity of viral probe in quantitative antigen detection by performing immunoassay. Prostate specific antigen (PSA) was detected by antibody in viral probe and the amount of PSA was quantified by SERS signal generating from gold nanoparticles in viral probe. From the increasing SERS intensity with the raise of PSA concentration, it is concluded that viral probe have selectivity for detecting antigen and can generate SERS signal corresponding to captured antigen. The M13 virus based SERS nanoprobe can pave the way for quantitative detection of antigen in infinitesimal range and offer great potential for improved medical diagnostics.
II3: Advanced Characterization
Tuesday PM, April 22, 2014
Moscone West, Level 3, Room 3006
4:30 AM - *II3.01
Plasmonic Interferometry: Physics and Applications
Domenico Pacifici 1 2 3
1Brown University Providence USA2Brown University Providence USA3Brown University Providence USAShow Abstract
Surface Plasmon Polaritons (SPPs) are fluctuations of the free electron density in metals coupled to electromagnetic waves. SPPs at optical frequencies show a significant momentum mismatch with respect to the light incident on a flat metal/dielectric interface, therefore coupling strategies generally rely on prisms (Kretschmann configuration) or metal gratings to excite them.
In this talk I will show alternative methods to generate SPPs at optical frequencies using light diffraction by individual nanocorrugations etched in metal films. In particular, I will show how nanometer scale slits, grooves and holes can be used as efficient, localized sources of SPPs.
Spatial localization of the source of SPPs allows for control of the SPP propagative phase, thus enabling researchers to perform "plasmonic interferometry," i.e. optical interferometry at the nano- and micro-scale using SPPs as the interfering waves.
By properly varying the nanoscatterer separation distance and in-plane distribution, the optical interference of SPPs can be spatially modulated and spectrally tuned. This property, together with the highly confined nature of SPPs, can be employed to enhance the optical absorption in thin film solar cells, and improve the sensitivity and selectivity of high-throughput, real-time biochemical sensors.
I will also discuss how Plasmonic Interferometry can be turned into a powerful tool to measure the coherence length of light sources, as well as determine the dispersion of optical constants of dielectric materials in a broad wavelength range.
5:00 AM - II3.02
Probing Coherent and Incoherent Radiation from Semiconductor and Plasmonic Nanostructures and Surfaces
Benjamin Brenny 1 Toon Coenen 1 Albert Polman 1
1FOM Institute AMOLF Amsterdam NetherlandsShow Abstract
We demonstrate a novel way to distinguish coherent and incoherent radiation from silicon and metallic nanostructures by using a nanoscale electron probe to generate light emission. We use angle-resolved cathodoluminescence imaging spectroscopy (ARCIS), in which a 30 keV electron beam in a scanning electron microscope is used as a broadband point-like excitation source. The transient electric field about the electron trajectory excites coherent transition radiation from the surface which is a direct measure of the local dielectric constant. In addition, incoherent radiation is excited by the recombination of electron-hole pairs generated by electrons penetrating into the silicon.
In our experiments we use a half-parabolic mirror placed between the electron column and the silicon sample to collect the electron beam generated coherent and incoherent emission. We collect angle-resolved radiation profiles over a spectral range from 400-900 nm. The data are fitted to a model that assumes dipolar radiation profiles for the transition radiation component and Lambertian profiles for the incoherent emission. Excellent agreement between the angular data and the theory is observed. The analysis enables partitioning the collected emission spectrum in coherent and incoherent parts. The coherent part serves as a nanoscale probe of the local dielectric constant, a property that can not be detected using far-field techniques at nanoscale resolution. Moreover, we reconstruct the incoherent radiation spectrum over the entire 400-900 nm spectral band.
The measurements are complemented with studies on thin-film and bulk samples of Au, Ag, Cu and Al. These plasmonic metals are all efficiently excited by the electron beam and their transition radiation spectrum is collected. Good agreement with theory is observed, based on dielectric constants measured using ellipsometry.
Overall, the ARCIS technique serves as a nanoscale probe of optical resonances in dielectric and plasmonic nanostructures, and enables measurements of optical constants at length scales that are inaccessible with any other technique.
5:15 AM - II3.03
Plasmonic Properties of Conductively and Capacitively Coupled Nanowire Dimers Investigated by Scanning Transmission Electron Microscopy
Ina Alber 1 Wilfried Sigle 2 Christina Trautmann 1 3 Peter A. van Aken 2 Maria Eugenia Toimil-Molares 1
1GSI Helmholtz Centre for Heavy Ion Research GmbH Darmstadt Germany2Max-Planck-Institute for Intelligent Systems Stuttgart Germany3Technical University Darmstadt Darmstadt GermanyShow Abstract
Surface plasmon resonances in metallic nanostructures are attracting great interest due to their property to enhance the electromagnetic field of light in the nanostructure nearfield. Recently, much interest is given to the plasmonic properties of nanoparticles separated by small gaps or connected by junctions of varying size. These structures are platforms to investigate the coupling between electronics and plasmonics as relevant for example for sensing and molecular switching .
We present surface plasmon resonance measurements on conductively and capacitively coupled nanowire dimers by electron energy-loss spectroscopy (EELS) combined with scanning transmission electron microscopy (STEM). The investigated dimers are created by adjusting the synthesis conditions during pulsed electrodeposition of AuAgAu segmented nanowires and the subsequent acidic dissolution of Ag. The dimers have lengths in the µm-range and diameters of about 100 nm. A capacitively coupled dimer is formed by two nanowires separated by a small gap, the smallest gap being about 8 nm. For the conductively coupled dimers, two wires are connected by metallic junctions with varying diameters. Our results are compared to finite element simulations using CST Microwave Studio.
Our EELS-STEM measurements visualize for capacitively coupled dimers the generation of bonding and antibonding mode pairs up to the third multipole order.  For the conductively coupled dimers, we find that an increase in junction size does not shift significantly the antibonding modes. However, it causes a strong blue shift of the bonding modes, leading to an energetic mode rearrangement compared to the mode arrangement of a capacitively coupled dimer with similar dimensions.  The shift of the bonding modes is analysed as a function of connection size and multipole order.
In addition, the influence of the dimer symmetry on the resulting EEL spectrum is discussed.
 Perez-Gonzalez, O., Zabala, N., and Aizpurua, J., New J. Phys 13 (2011) 083013.
 Alber, I., Sigle, W., Mueller, S., Neumann, R., Picht, O., Rauber, M., van Aken, P. A., Toimil-Molares, M. E. ACS Nano 5 (2011), 9845-9853.
 Alber, I., Sigle, W., Demming-Janssen, F., Neumann, R., Trautmann, C., van Aken, P. A., Toimil-Molares, M. E., ACS Nano 6 (2012) 9711-9717.
5:30 AM - II3.04
Independent Tuning of Surface Plasmon Energy, Extinction Coefficient and Scattering Cross-Section via Compositionally and Architecturally Complex Nanorods
Kyoungweon Park 1 Sushmita Biswas 1 Dhriti Nepal 1 Richard A Vaia 1
1Air Force Research Laboratory Wright-Patterson AFB USAShow Abstract
The interaction strength of light with metallic nanorods (extinction cross-section) is determined by the strength of the scattering (radiative) and absorptive (non-radiative) processes that occur at the local surface plasmon resonance (LSPR). Since the components of the extinction cross section depend differently on particle volume, independent synthetic control of particle size, composition and shape enables extensive tailoring to address diverse application needs, such as maximal near field enhancement, far-field scattering magnitude, or heat generation. Unfortunately the relationships between structure, composition and extinction, scattering and absorptive cross-sections have not been explicitly demonstrated. The availability of only a few experimental reports is mainly due to challenges obtaining and verifying a series of precise concentrations of compositionally-pure, nanorod dispersions that have an independent variation of particle volume and aspect ratio. Here in, we address this challenge by bringing together synthetic procedures that provide independent tuning of the gold nanorod (AuNR) structure (effective volume, aspect ratio, length, and diameter range of 500x, 3x, 4x and 3x, respectively), with robust characterization of the composition and structural purity. We further fabricate core-shell structures (Ag, Pd, Pt, S,and Se) to selectively enhance the desired optical response. The accuracy and validity of the existing theoretical calculations are verified; for example demonstrating the scaling of extinction cross-section and the relative contribution of scattering on rod architecture and composition. This refined, quantitative structure-property correlation provides a solid platform to engineer plasmonic nanoparticles beyond AuNRs for emerging applications.
5:45 AM - II3.05
All-Optical Control of THz Plasmonic Surfaces
Giorgos Georgiou 1 Hemant K. Tyagi 1 Martijn C. Schaafsma 1 Jaime Gomez Rivas 1 2
1FOM Institute AMOLF Amsterdam Netherlands2COBRA Research Institute Eindhoven NetherlandsShow Abstract
We investigate the photo-excitation of localized surface plasmon polaritons (LSPPs) in semiconductor plasmonic resonators at THz frequencies. This is realized by a patterned optical excitation of free charge carriers in thin films of GaAs using a spatial light modulator. This enables full spatial and temporal control of plasmonic resonances. By changing the illumination patterns we are able to excite LSPPs in plasmonic resonators without the need of physically structuring the sample. A single semiconductor layer can be thus used to generate a variety of plasmonic devices. Furthermore, using this concept we were able to observe transfer of surface plasmon polaritons in loaded plasmonic antennas. Moreover, this approach can be used for photo-generating plasmonic waveguides and circuits.
II4: Poster Session I
Tuesday PM, April 22, 2014
Marriott Marquis, Yerba Buena Level, Salons 8-9
9:00 AM - II4.02
Fabrication of Ordered QD-AuNR Clusters: Plasmon Enhanced Fluorescence in Solution and In Patterned Arrays
Kyoungweon Park 1 Dhriti Nepal 1 Sushmita Biswas 1 Lawrence F Drummy 1 Xiaoying Liu 2 Paul Nealey 2 Richard A Vaia 1
1Air Force Research Laboratory Wright-Patterson AFB USA2University of Chicago Chicago USAShow Abstract
Control of photon absorption and emission is at the core of many emerging photonic technologies, ranging from photovoltaics and sensors to single photon emitters for quantum encryption. Recently, plasmon-exciton coupling has been demonstrated as a means to tailor the efficiency of emission by optimizing the overlap between the emissive state and the localized surface plasmon resonance. Fabrication of such plasmon-exciton structures by colloidal approaches offers numerous advantages relative to lithographic techniques, including controllable sub 5 nm gap size, 3D architectures and higher throughput, if challenges can be overcome, such as heterogeneous products, poor colloidal stability, and unacceptable pattern variability for device registration. Herein we discuss an interface and assembly method using orthogonal chemical interactions that provide pattern arrays with high yield and specificity of quantum dot (QD) gold nanorod (AuNR) architectures. Specifically, poly(ethylene glycol)-grafted-AuNRs in water selectively adsorb to polystyrene (PS) brushes. Number density, spacing and local orientation of the adsorbed AuNRs depend on the dimensions and shape of the chemical contrast pattern based on the PS brushes. The inert polymer and dithiol coupling directs subsequent QD binding to the adsorbed AuNRs, leaving a QD-free surface. Tuning the pattern, assembly and coupling conditions afford excellent control over spacing (1-10 nm), location (ends vs. all around), and number of QDs per AuNR. Following similar coupling approaches, bulk solutions of QD-AuNRs architectures, also with controlled spacing, QD/AuNR ratio and long-term colloidal stability, are demonstrated. The non-resonant photoluminescent enhancement of these structures was 5x, which is almost 70% of theoretical maximum and demonstrating the feasibility for applications ranging from biological sensing to advanced optical communication.
9:00 AM - II4.03
Broad Color Manipulation Technologies for White Mechanoluminescence
Soon Moon Jeong 1 Seongkyu Song 1 Kyung-Il Joo 1
1Daegu Gyeongbuk Institute of Science and Technology Daegu Republic of KoreaShow Abstract
Since mechanoluminescence was discovered by Francis Bacon, a variety of mechanoluminescent materials have been developed. Until now, many materials have been known to emit light by the application of stress even though scientists have not yet arrived at a clear understanding of the effect. However, no practical application has been realized because previous instances of mechanoluminescence have been weak and unrepeatable. To overcome these shortcomings, elastico-mechanoluminescent materials have been developed, which generate the luminescence during deformation of solids without fracture or tribo-reactions. Recently, we designed and demonstrated flexible composite films with highly bright and durable characteristics by focusing on the substance (polydimethylsiloxane; PDMS) that transfers the mechanical stress to the mechanoluminescent materials (copper-doped zinc sulfide, ZnS:Cu). By employing transparent PDMS with a high elastic modulus, we were able to realize in a simple manner a brightness of ~120 cd/m2 and durability over ~100,000 repeated motions.
The development of color manipulation technology would thus open a door for exploiting mechanoluminescence in light source and imaging devices. We demonstrated the color manipulation of mechanoluminescence by controlling the concentration of two independent mechanoluminescent materials (ZnS:Cu,Mn and ZnS:Cu) in a PDMS matrix. We show that the color can be tuned linearly by regulating the weight ratio of the mechanoluminent materials and the color region in the chromaticity diagram can be extended by increasing the stress rate. We also reported that by applying mechanical stress, a colorful patterned imaging device and white lighting source can be produced.
However, one of the major drawbacks in PDMS based mechanoluminescent composite films is a difficulty of blue color demonstration due to its soft matrix. Even when a composite film is fully stretched, the compressive stress is insufficient to emit blue luminescence. Actually, the composite film with blue phosphors shows green luminescence rather than blue. In this presentation, we used combination of alternative stress applying methods and general organic dyes to demonstrate deep blue luminescence. Based on this approach, we also achieved various white mechanoluminescence. We believe that the findings of this color manipulation technology can open a new window for developing new smart systems and opto-mechanical devices.
 S. M. Jeong, S. Song, S. -K. Lee, and B. Choi, Appl. Phys. Lett. 102, 051110 (2013).
 S. M. Jeong, S. Song, S. -K. Lee, and N. Y. Ha, Adv. Mater. (in press), doi:10.1002/adma.201301679.
9:00 AM - II4.05
Plasmonic Nanoflower Assembly for Uniform and Reproducible SERS Substrate
Kinam Jung 1 Jungsuk Hahn 2 Sungjun In 1 Yongjun Bae 1 Heechul Lee 3 Peter Pikhitsa 1 Kwangjun Ahn 1 Kyungyeon Ha 1 Junhoi Kim 1 Jongkwon Lee 1 Sunghoon Kwon 1 Namkyoo Park 1 Mansoo Choi 1
1Seoul National University Seoul Republic of Korea2Samsung Display Hwaseong Republic of Korea3Samsung Electronics Suwon Republic of KoreaShow Abstract
In this research we develop novel SERS substrate utilizing flower-like 3D nanoparticles array via IAAL(ion-assisted aerosol lithography) method for uniform and reproducible Raman signal with high field enhancement. We demonstrate the control of hot-spots (in terms of their locations and intensities) as a function of the petal number m (4, 6, and 8). Electromagnetic calculations show that hot-spots that are formed in 3D nanogaps located between adjacent petals exist between petals and their intensities increase with the number of petals. The obtained SERS enhancement factor is ~ 10^7, sufficient for the single molecule detection. Quantitative and qualitative optical behaviors of fabricated 3D multipetal flower assemblies are also studied by measuring dark field (DF) spectra. Enhanced excitation of non-radiative higher order surface plasmon modes for the higher m-petal flowers is also interpreted in terms of m-petal geometry, in agreement with the results of SERS, DF spectra, and rigorously calculated electromagnetic field.
9:00 AM - II4.06
Hierarchical Nanostructures Created by Interference of Multiple Beams from High Order Diffraction
Tae Yoon Jeon 1
1KAIST Daejeon Republic of KoreaShow Abstract
Periodic and hierarchical nanostructures have been intensively studied for a wide range of applications for photonic microsensors. For example, dielectric structures possess photonic bandgap and metallic nanostructure exhibit surface-enhanced Raman scattering (SERS); both properties are highly sensitive to environment, thereby being useful for microsensors. However, fabrication of such hierarchical nanostructures still remains a challenge. Conventional photolithography has limitations in definition of structures due to diffraction limit. Furthermore, to create various designs of patterns, same number of photomasks is required. Although E-beam lithography and focused ion beam lithography enable the preparation of nanostructures, their complex and time-consuming fabrication processes makes the techniques impractical.
Here, we demonstrate a facile and versatile method for creating various designs of hierarchical nanostructures using novel interference lithography. A monochromatic plane wave which propagates through diffraction grating produces three dimensional patterns of light intensity by interference of diffracted beams. This near-field pattern is repeated with a period which is called Talbot distance. When the grating period is comparable with wavelength of incident light, zero- and first- order diffraction are available, which results in the generation of well-defined simple 3D profile of light intensity; this profile can be transferred into photoresist to create 3D nanostructure. To increase complexity of the 3D profile, larger grating period can be employed. This leads to high order diffraction from the grating, thereby generating highly complex 3D profile through the interference of multiple diffracted lights. For example, with a grating period of 2000 nm and the wavelength of incident light of 325 nm, we can generate up to 6th order diffraction and therefore, 7 different beams form a complex profile of light intensity. 2D slice of the intensity profile can be transferred into thin film of photoresist. By controlling a distance between the diffraction grating and the photoresist, a variety of 2D nanopatterns are created, of which structures are highly complex; from each 2D pattern, various unit structures such as doughnut, square, diamond, mesh, flower shapes are observed. One point that is worth stressing is that all the structures are prepared by single phase mask by simply controlling the distance between grating and photoresist film. Full 3D interference pattern and its 2D slice are in good agreement with calculations from finite-difference time-domain (FDTD) method. We use one of various 2D patterns, composed of the elliptical nanohole arrays in rectangular coordination, as template for creation of SERS-active substrate. Dense arrays of four elliptical gold dots have hot spots at their interstices with nanoscale gaps, which enable the highly efficient light confinement and therefore high degree of enhancement in SERS signal.
9:00 AM - II4.07
Surface-Enhanced Raman Scattering Substrates Based on Plasmonic Lenses
Semih Cakmakyapan 1 2 Neval Cinel 2 Ekmel Ozbay 1 2 3
1Bilkent University Ankara Turkey2Nanotechnology Research Center Ankara Turkey3Bilkent University Ankara TurkeyShow Abstract
The study of interactions of molecules or molecular structures with plasmonic nanostructures is a rapidly growing research area having significant impact on several applications such as surface-enhanced Raman spectroscopy. The localized surface plasmons (LSPR) are excited on isolated nanostructures such as nanoparticles or lithographically prepared nanostructures . The properties of surface plasmons depend on the thickness of metal film, type of the metal and roughness of the metal surfaces and dielectric constant of the adjacent medium. Incident electromagnetic field can be enhanced and localized in the slit region of a metal film . This localized field couples surface plasmons on the surface of the metal.
In this study, circular plasmonic lens with different ring diameter and slit width were prepared by electron beam lithography (EBL) and the influence of plasmonic lens structure on SERS enhancement was investigated. We have demonstrated the influence of plasmonic lens properties (inner diameter and slit width) on SERS performance. The SERS intensity obtained from plasmonic lens having 3.0 µm inner diameter is 13.2 times higher compared to planar silver thin film which is consistent with the theoretical calculations . Then, we present our preliminary results in designing plasmonic nano-patterned structures that can work as highly efficient SERS substrates. The proposed design gives more than two orders of magnitude larger signal intensity than plain gold film and nearly one order of magnitude larger than an optimally designed “etched-ring” plasmonic lens structure . The relationship between the signal intensity and the physical sizes and parameters such as slit width, number of rings, thickness and material of separation layer and period should also be further studied. This study suggest that the strong relationship between the surface plasmons and SERS activity can be used to built unique structures to prepare well-defined arrays to use in several applications of SERS.
1. K. A. Willets, and R. P. Van Duyne, Annual Review of Physical Chemistry 58, 267-297 (2007).
2. Y. Xie, A. R. Zakharian, J. V. Moloney, and M. Mansuripur, Opt Express 12, 6106-6121 (2004).
3. M. Kahraman, S. Cakmakyapan, E. Ozbay, and M. Culha, Annalen Der Physik 524, 663-669 (2012).
4. Neval Cinel, Semih Cakmakyapan, Gulay Ertas, and Ekmel Ozbay, JSTQE-INV-NP-04491-2012.
9:00 AM - II4.09
Localized Surface Plasmon Decay Dynamics
Prineha Narang 1 Adam Jermyn 1 Ravishankar Sundararaman 2 William A. Goddard 2 Giulia Galli 3 Harry A. Atwater 1
1California Institute of Technology Pasadena USA2California Institute of Technology Pasadena USA3University of California, Davis Davis USAShow Abstract
Recent experimental observations of hot carrier generation and transport in metals require a quantum mechanical description to account for phenomena that contradict the classical Fowler theory for metal-semiconductor interface transport. In this context we present calculations for quantized plasmon fields indicating a correlation between plasmon polarization and the distribution of electron momenta resulting from the prompt decay of plasmons to excited ‘hot&’ carriers. Specifically, we report results of calculations for Au nanoantennas indicating that decay of localized plasmons to excited electrons and holes in an optical antenna results in strongly anisotropic momentum distributions for the excited carriers, in the regime prior to inelastic carrier relaxation. The hot carrier concentration and momentum anisotropy are strongly dependent on both the density of plasmonic modes excited by incident light and the way in which these modes align with the underlying metallic lattice. We discuss the role of virtual plasmons in nanoantenna-based devices, as well as the relative importance of interband and intraband transitions on the timescales of interest. The energy distribution of hot carriers after excitation, role of multi-photon excitation processes and correlation with plasmon polarization will be discussed using the model we have developed. Finally, we compare our theoretical predictions with experimental observations in solid-state nanoantenna-based energy conversion systems.
9:00 AM - II4.10
Tailoring the Plasmon Couplings in High Density Gold Nanostar Assemblies on Metal and Dielectric Films
Jiwon Lee 1 Bo Hua 2 Seungyoung Park 1 Minjeong Ha 1 Youngsu Lee 1 Zhiyong Fan 2 Hyunhyub Ko 1
1Ulsan National Institute of Science and Technology(UNIST) Ulsan Republic of Korea2Hong Kong University of Science amp; Technology (HKUST) Hong Kong SAR ChinaShow Abstract
Surface plasmons in metal nanostructures have attracted considerable attentions for applications in nanophotonics and surface-enhanced Raman scattering (SERS) chemical sensors. Here we investigate the particle-film plasmon couplings of high-density gold nanostar (GNS) assemblies arranged on various metal and dielectric substrates (silver, gold, silicon, glass). In particular, we show how the GNS surface densities (or interparticle gap separations) affect the E-field enhancements from the particle-film plasmon couplings by analyzing the finite-difference time-domain (FDTD) calculation of E-fields and the experimental SERS intensities. We also present the interplay between the interparticle and particle-film plasmon couplings of high-density gold nanostars (GNSs) on metal and dielectric films as a function of interparticle separation. We show that the SERS enhancement factor (EF) of GNSs on a metal film as a function of interparticle separation follows a broken power law function, where the EF increases with the interparticle separation for the strong interparticle coupling range below an interparticle separation of ~0.8 times the GNS size, but decreases for weak interparticle coupling range (for an interparticle separation > 0.8 times the GNS size). Finally, we demonstrate optimally designed SERS substrates based on gold nanostar assemblies on a metal film which can detect attomole level of nitroaromatic explosives.
9:00 AM - II4.11
The Design of Sensing for Bio-Macromolecules on Side-Polished Optic Fiber with the Magnification of Surface Enhanced Raman Scattering Caused by Deterministic Aperiodic Arrays
Kuang Yu Chen 1 Yung Tang Nien 2 In Gann Chen 1
1Department of Materials Science and Engineering, National Cheng Kung University Tainan Taiwan2Department of Materials Science and Engineering, National Formosa University Yunlin TaiwanShow Abstract
Basing on the sensitivity, speed and convenience, surface enhanced Raman scattering (SERS) is thought to be a powerful tool applying to bio-medical analysis. This technique may give high identification to organic samples without changing the original properties of them.
The hot-spot effect of SERS is concerned of the electric field distribution induced by surface plasma resonance (SPR). Usually, between the gap of noble metal nanoparticles or on the sharp tip area, where there is stronger electric field, there would be stronger enhancement. However, such gap area is so narrow and that restricts the application of hot-spot effects to macromolecules like proteins and viruses.
Previous study showed that with proper order, so-called deterministic aperiodic arrays of nanostructrures might give huge hot-spot area of hundreds nanometers. And the enhancement factor could reach ~10^7. We think the area is big enough to load macromolecules.
In our study, we prepared gold nano cylinders on silica wafer by electron beam lithography (EBL). The order of the array referred to the information from the previous article. After dropping the rhodamine 6G aqueous solution on our chip, we covered it on the polished site of the side-polished optic fiber (SPOF) connected to our home made Raman spectrometer with 532 nm laser source. The enhancement factor was calculated as ~10^5.
We are now trying to deposit indium tin oxide (ITO) on the SPOF to provide better conductivity that EBL needs, because we are also planning to copy the same array to SPOF. In this design, we can change the optic fiber after every single use to prevent the possibility of bio-contamination from dirt optic fiber.
Previous research showed ITO could be compatible for antibody conjugation after certain modifications. We wish the deposition of antibody could provide specificity for disease screening. Besides, with the advantage of optic fiber, this system could be capable of out-door or homecare usages.
9:00 AM - II4.12
Structural Color Based on Multilevel Optical Microcavity by Microcontact Printing
In-Ho Lee 1 Sin-Hyung Lee 1 Chang-Min Keum 1 Sin-Doo Lee 1
1Seoul National University Seoul Republic of KoreaShow Abstract
Recently, the structural color has attracted great interest due to its potential as an alternative for colorant pigmentation. In contrast to conventional color pigments, the structural color is endurable to constant illumination with strong light intensities and does not require complicated processes of patterning multilayers for different colors on a single substrate . For designing the structural color, a variety of methods such as a photonic crystal , a plasmonic nanostructure , and an optical microcavity  have been introduced so far. Among them, the optical microcavity-based approach is most promising because of the simple fabrication and the polarization-independent optical property. Moreover, compared to other kinds of the structural color, it is more versatile in that it can be fabricated either in a transmission or a reflection type . However, it is difficult for the optical microcavity-based approach to realize three primary colors, red, green, and blue, on a single substrate since different microcavities are required for different colors.
In this study, we present a multilevel architecture of different optical cavities for different colors on a single substrate by microcontact printing. For fabricating the multilevel optical microcavities, patterns of a fluorous polymer (EGC-1700, 3M), used as a dielectric material, were printed on an aluminum reflector using an elastomeric stamp made of poly(dimethylsiloxane). A semi-transparent metallic film was then prepared on the multilevel dielectric layer by vacuum deposition. In this configuration, the structural color corresponding to the thickness of the optical microcavity was obtained under ambient light. This multilevel architecture provides a viable tool of fabricating color patterns for a variety of visual applications such as textile and decoration.
 T. Xu , H. Shi, Y. Wu , A. F. Kaplan , J. G. Ok , and L. J. Guo, Small 7 (2011) 3128.
 S. Kinoshita, S. Yoshioka, and J. Miyazaki, Rep. Prog. Phys. 71 (2008) 076401.
 S. Yokogawa, S. P. Burgos, and H. A. Atwater, Nano Lett. 12 (2012) 4349.
 Y. Yoon and S. Lee, Opt. Express 18 (2010) 5344.
 Y. Chena, and W. Liua, Optik 124 (2013) 13.
This work was supported by the National Research Foundation of Korea under the Ministry of Education, Science and Technology of Korea through the grant 2011-0028422.
9:00 AM - II4.13
Solution Processable SERS Substrates
Elena Khon 1 Pavel Moroz 1 Mihkail Zamkov 1
1Bowling Green State University Bowling Green USAShow Abstract
Surface enhanced Raman spectroscopy (SERS) is a great analytical tool to obtain information on molecular composition. This technique has gained a reputation as one of the most sensitive spectroscopic methods available for the detection of a wide range of adsorbate molecules down to a single molecule detection limit. The most investigated metals for SERS substrates are gold (Au) and silver (Ag). Unfortunately, the fabrication of such devises poses a significant challenge due to an expensive deposition technology including, vapor deposition, electron-beam lithography, focused ion-beam lithography, and nano-transfer printing. Herein, we introduce a simple and low-cost approach to fabricate SERS substrates using roll-to-roll printing of matrix encapsulated gold nanoparticle arrays. The enhancement of Raman signals obtained using these materials was found to be comparable to commercially available SERS substrates. We expect that an on-going optimization of the film morphology should yield further enhancement of the demonstrated SERS architecture.
9:00 AM - II4.14
Omidirectional Antireflection Nanostructures Nanoimprinted by Density-Graded Nanoporous Silicon Template
Shang-Jung Yang 1 2 Yu-Hsuan Ho 1 Ming-Chih Tsai 1 Kuan-Han Ting 1 2 Pei-Kuen Wei 1 2
1Academia Sinica Taipei Taiwan2National Taiwan Ocean University Taipei TaiwanShow Abstract
We present a convenient and low-cost method to fabricate large-area polycarbonate AR nanostructures to improve the luminous intensity and image clarity of a commercial 2.0-inch display panel in bright condition. The polycarbonate AR nanostructures were nanoimprinted by the graded-density nanoporous silicon template with nanoparticle-catalyzed etching. The average reflectivity of the AR film in visible wavelength was reduced from 10.2% to 4.8% in the optimized case. After attaching on the display panel to reduce the light reflection on the substrate, the brightness enhancement and decrease of ambient light reflection were observed. Due to the enhancement of contrast ratio, the quality index of the Lena image test was improved from 0.85 to 0.92 under strong ambient illumination.
9:00 AM - II4.17
Nanometer Scale Epitaxial Lateral Overgrowth of AlN by Self-Assembled Patterning
Michele Ann Conroy 1 2 3 Haoning Li 1 2 Vitaly Zubialevich 1 Nikolay Petkov 1 Justin Holmes 1 2 3 Peter Parbrook 1 2
1Tyndall National Institute Cork Ireland2University College Cork Cork Ireland3Centre for Research on Adaptive Nanostructures and Nanodevices Dublin IrelandShow Abstract
There has been intensive research into the manufacturing of nitride based ultra violet light emitting diodes (UV LEDs) as the solution to the current bulky and high voltage UV light emitting Hg lamps, for its many useful applications including water purification. However these devices suffer from low efficiency (~2%) compared to the long established blue emitting InGaN LEDs (~70%). There are many different reasons for this performance issue, with high threading dislocation densities (TDDs) having one of the greatest impacts. Epitaxial Lateral Overgrowth (ELOG) has been a long established method of decreasing TDDs in nitrides. However patterning for ELOG is usually done by expensive lithographic processes often not reproducible on a large scale. In this study silica sphere lithography was applied to the initial growth layer in the multiple quantum well (MQW) structure by a self-assembly method. This simple process of producing a uniform patterned surface throughout the wafer, allowed for subsequential overgrowth in the Metal Organic Vapour Phase Epitaxy (MOVPE) reactor. The nano dimensions compared to usual micron scale patterns used for ELOG typically results in less time required for overgrowth. These layers fully coalesce by 500nm of growth much shorter compared to the reported ~7µm for micron scale patterns1 and even to the latest nano scale patterns at 2µm in AlN ELOG2. Transmission electron microscopy studies show the dislocation density has more than halved compared to the un-patterned AlN buffer layer under the same growth conditions, and almost completely eliminated the edge type. Another advantage of using this patterning visible by in situ MOVPE curvature measurements is the reduction in strain built up during growth resulting in the reduction of wafer bowing. The UV light emitting quantum wells can now be grown on a high crystal quality AlN buffer layer, leading to the decrease in non radiative recombination paths due to dislocations.
1. Zeimer, U., et al. Journal of Crystal Growth 377(2013)32-36
2. Dong, P., et al. Applied Physics Letters 102 (2013): 241113.
9:00 AM - II4.18
Plasmon-Enhanced Upconversion Luminescence in Individual Nanophosphor-Nanorod Structures Formed Through Template-Assisted Self-Assembly
Nicholas J. Greybush 1 Marjan Saboktakin 2 Xingchen Ye 3 Soong Ju Oh 1 Cristian Della Giovampaola 2 Nathaniel E. Berry 1 Nader Engheta 2 1 4 Christopher B. Murray 3 1 Cherie R. Kagan 2 1 3
1University of Pennsylvania Philadelphia USA2University of Pennsylvania Philadelphia USA3University of Pennsylvania Philadelphia USA4University of Pennsylvania Philadelphia USAShow Abstract
We demonstrate plasmonic enhancement of the luminescence of single upconversion nanophosphors (UCNPs) deterministically assembled in close proximity to the tips of gold nanorods (Au NRs). Individual UCNPs, composed of hexagonal phase NaYF4 doped with Yb3+ and Er3+, as well as single Au NRs are precisely positioned in lithographically defined templates via capillary assembly techniques. The Au NR aspect ratio is tailored to tune the localized surface plasmon resonance (LSPR) for longitudinally polarized excitation to match the 980 nm excitation wavelength of the UCNPs. The UCNP luminescence is characterized by scanning fluorescence microscopy in both the presence and absence of a Au NR. We observe a polarization-dependent luminescence enhancement: polarizing the incident laser beam along the axis of the Au NR resonantly excites its longitudinal LSPR, resulting in strong optical near-fields surrounding the NR tip where the UCNP is located. Longitudinal versus transverse excitation results in at least a 2x greater luminescence enhancement. Because the upconversion emission is a nonlinear process, the power dependence of the luminescence enhancement is also investigated. The template-based co-assembly scheme utilized here for plasmonic coupling offers a versatile platform for improving our understanding of optical interactions among individual chemically prepared nanocrystal components.
9:00 AM - II4.19
Virus Based Novel Reflective Display
Chuntae Kim 1 Won-Geun Kim 2 So-Young Lee 1 Jin-Woo Oh 1 2
1Pusan National University Busan Republic of Korea2Pusan National University Busan Republic of KoreaShow Abstract
Reflective displays have attracted a lot of attention because of their low power consumption, simple manufacturing process, without the backlighting source. Many researchers have presented various types of reflective displays, such as cholesteric liquid crystal displays, bistable nematic liquid crystal displays, zenithal bistable displays with bistability, electrophorectic displays (EPD), and interferometric modulator displays. Among these, nowadays reflective liquid crystal displays (RLCDs) have been studied mainly for use in mobile devices, outdoor signboard applications, and e-books. Here, we developed novel reflective photonic device for low-voltage tunable full color display. The structural color matrix was made of virus (M-13 bacteriophage) through self-assembly process reported in our 2011 Nature paper. Recently, virus has been applied to various electronic devices due to its well known liquid crystal behavior property. Upon application of low bias voltage (<0.2V), the virus based nanostructure immediately exhibited the desired colors through structure modulation. We performed the various letters and numbers using the self-designed 7-digits display device with patterned micro-heater. We expect that virus based color display device will be used for next generation full-color displays.
9:00 AM - II4.20
Plasmonic Interferometry for Glucose Sensing with Enhanced Sensitivity and Selectivity
Jing Feng 1 Vince S. Siu 1 2 Patrick W. Flanigan 1 G. Tayhas R. Palmore 1 2 3 Domenico Pacifici 1 2
1Brown University Providence USA2Brown Univeristy Providence USA3Brown Univeristy Providence USAShow Abstract
Plasmonics is a rapidly emerging field of nanophotonics that focuses on the ability of noble metal nanostructures to manipulate light. For example, by using nanocorrugations etched in a metal film, light at optical frequencies can be coupled to surface plasmon polaritons (SPPs), electromagnetic waves that propagate along a metal-dielectric interface. SPPs are confined at the metal surface and are very sensitive to small changes in the refractive index of the dielectric (e.g. aqueous solutions with biochemical analytes).
We have recently reported on a compact, high-throughput plasmonic sensor based on plasmonic interferometry optimized for real-time monitoring of glucose in aqueous solutions . The sensor consists of a spatially dense, planar array of plasmonic interferometers (with a density >1,000/mm2), where each interferometer is composed of two 200nm-wide, 10µm-long grooves flanking a 100nm-wide slit etched in a 300nm-thick silver film. The distances between each groove and slit were varied between 0.25 to 10µm in steps of 25nm. The detection limit of the plasmonic sensor for glucose in aqueous solutions is 5.5mu;M with a sensitivity of 105,000%/RIU (refractive index units) or 0.2 × 105 % / M at 590nm.
In order to improve the sensor selectivity to glucose, we adopt a novel molecular recognition scheme that couples plasmonic interferometry with dye chemistry, specifically the Amplex Red enzyme assay. In this implementation, glucose oxidase is added in solution to rapidly convert D-glucose into D-gluconolactone and H2O2 in a 1:1 stoichiometry. The H2O2 reacts with horseradish peroxidase (HRP) to oxidize Amplex Red into Resorufin, a dye molecule which is characterized by a strong optical absorption coefficient at ~571nm. The reaction is monitored in real-time by simply measuring changes in the light intensity transmitted through the slit of each interferometer.
This device is both highly sensitive, with a measured intensity change of 1.7 × 105 % / M (i.e. about one order of magnitude more sensitive than without assay) and selective for glucose in picoliter samples, across the physiological range of glucose found in human saliva (20 minus; 240 mu;M). Since plasmonic interferometry enables spectroscopic fingerprinting of a sample and the assay is selective for glucose, the detection of glucose is possible within a complex mixture of proteins, small molecules, and