A strip-loaded channel waveguide was fabricated by deposition of Au nanoparticles (AuNPs) in a thin strip via organometallic chemical vapor deposition on top of a polystyrene slab waveguide. The beam confinement is demonstrated experimentally, despite the absence of a classical closed layer for strip loading. The AuNP density conditions for plasmonic-waveguide hybrid transmission devices are discussed.
Harvesting solar energy is a promising solution toward meeting the world’s ever-growing energy demand. Dye-sensitized solar cells (DSSCs) are hybrid organic–inorganic solar cells with tremendous potential for commercial application, but they are plagued by inefficiency due to their poor sunlight absorption. Plasmonic silver nanoparticles (AgNPs) have been shown to enhance the absorptive properties of DSSCs, but their plasmonic resonance can cause thermal damage resulting in cell deterioration. Hence, the influence of Zr-doped TiO2 on the efficiency of plasmon-enhanced DSSCs was studied, showing that 5 mol.% Zr-doping of the photoactive TiO2 material can improve the photovoltaic performance of DSSCs by 44%. By examining three different DSSC designs, it became clear that the efficiency enhancing effect of Zr strongly depends on the proximity of the Zr-doped material to the plasmonic AgNPs.
Nanopatterns resulting from two-beam interference in single, double, and multiexposures were simulated. Several patterns were experimentally fabricated to compare with the simulated patterns, allowing judgment of the quality of the simulation tool. Experimental and simulation results were consistent for single and double exposures. Photoresist nanofibers attached and detached from the substrate were fabricated with few changes in the development process. Results show that by increasing the number of exposures, a wide variety of patterns with very fine structures and sophisticated geometries can be generated. Fresnel-lens type structures are formed when the number of exposures is increased. These Fresnel-like patterns might have potential use in obtaining radial and azimuthal polarizations and optical vortices in addition to areas such as security patterns and diffractive optical elements.
We present a three dimensional (3D) metallic nanostructure, which has transmission resonance properties related to both localized surface plasmons and propagating surface plasmon polaritons. Various geometrical dimensions of the 3D metallic nanostructures were studied by means of simulation and experiment with respect to resonance position, resonance line width and bulk sensitivity. Narrower resonance line width and higher bulk sensitivity were achieved for the 3D nanostructure compared to conventional nanohole arrays. Finally, a 3D metallic nanostructure functionalized with a biotinylated thiol could detect streptavidin, suggesting the device may have potential as a bio-sensor.
The fabrication details to form large area systematically changing multishape nanoscale structures on a chip by laser interference lithography (LIL) are described. The feasibility of fabricating different geometries including dots, ellipses, holes, and elliptical holes in both x - and y - directions on a single substrate is shown by implementing a Lloyd’s interferometer. The fabricated structures at different substrate positions with respect to exposure time, exposure angle and associated light intensity profile are analyzed. Experimental details related to the fabrication of symmetric and biaxial periodic nanostructures on photoresist, silicon surfaces, and ion milled glass substrates are presented. Primary rat calvarial osteoblasts were grown on ion-milled glass substrates with nanotopography with a periodicity of 1200 nm. Fluorescent microscopy revealed that cells formed adhesions sites coincident with the nanotopography after 24 h of growth on the substrates. The results suggest that laser LIL is an easy and inexpensive method to fabricate systematically changing nanostructures for cell adhesion studies. The effect of the different periodicities and transition structures can be studied on a single substrate to reduce the number of samples significantly.
Waveguide evanescent field fluorescence microscopy (WEFF) is a novel microscopy technology that allows imaging of a cell's plasma membrane in the vicinity of a glass substrate with high axial resolution, low background and little photobleaching. Time-lapse imaging can be performed to investigate changes in cell morphology in the presence or absence of chemical agents. WEFF microscopy provides a method to investigate plasma membranes of living cells and allows a comparison to simplified model membranes immobilized on planar substrates. The interaction of the nonionic detergent Triton X-100 with plasma membranes of osteoblasts in an aqueous environment was investigated. Solubilization of the membranes very close to the waveguide surface was visualized and related to the three-stage solubilisation model proposed for liposomes and supported lipid bilayers. Findings for the plasma membranes of cells are in excellent agreement with results reported for these artificial model systems.
Two-step ion-exchanged waveguides with high surface refractive indices are fabricated under a variety of conditions. By modifying the conventional two-step ion exchange, the losses and the effective diffusion depth can be decreased without a significant effect on the surface refractive index. The influence of the first step, K+-Na+ ion exchange, performed time dependably on the surface refractive index change is investigated. Energy-dispersive x-ray spectroscopy is performed to establish the diffusion profiles of various ions.
Waveguide evanescent field fluorescence (WEFF) microscopy is a new development that allows the imaging of contact regions between biological cells and their substratum, as well as imaging of ultrathin films such as monomolecular Langmuir-Blodgett (LB) films. Mixed-lipid monolayer systems mimicking lung surfactant were fabricated on waveguides using the LB technique and imaged by both WEFF and standard wide field epi-fluorescence microscopy. These two technologies were compared with respect to contrast, photobleaching, and sensitivity. It was found that WEFF microscopy produced images with a much higher contrast, lower photobleaching, and higher sensitivity. In addition, fine structures in the lipidic domains were observed for the first time.
Total internal reflection fluorescence microscopy is an evanescent based fluorescence microscope providing a selective
visualization of cell-substrate contacts without interference from other, deeper cellular regions. Total internal reflection
fluorescence microscope is used extensively to visualize cell-substrate contacts. However, quantifying these contacts -
in particular the measurement of cell-substrate distances - has not been performed often. In order to quantify the cellsubstrate
distances we have developed a new theoretical method which is based on a change in the penetration depth of
the evanescent field by tuning the angle of incidence slightly above the angle of total internal reflection for s-polarized
light. This is simpler and much more accurate in comparison to the few existing approaches.
Planar glass waveguides with a specific number of modes were fabricated by Ag+-Na+ exchange in Schott SG11 glass. The effective refractive indices were determined using m-line spectroscopy in both s- and p-polarization. By using the reversed Wentzel-Kramers-Brillouin approximation, the index profiles were described by a nonlinear diffusion equation. The diffusion coefficients for Ag+ were established, as well as the penetration depth of the evanescent field in an aqueous environment for the different modes. The integrals of |E|2 fields for the evanescent-guided fields were investigated. These are important when evanescent fields are used for illumination in interface microscopy, an alternative method to total internal reflection fluorescence (TIRF) microscopy. The photoluminescent behavior of the waveguides was investigated as a function of ion exchange time and excitation wavelengths. Comparable images were obtained of fluorescently labeled HEK293 cells using TIRF microscopy and waveguide evanescent field fluorescence microscopy. Imaging was performed using HEK293 cells, delivering similar images and information.
We demonstrate an alternative to total internal reflection fluorescence (TIRF) microscopy. A method for imaging ultra
thin films and living cells located on waveguides illuminated with their evanescent fields is introduced. Analysis of ion-exchanged
waveguides focusing on their application as substrates for microscopic study of interfacial phenomena is
presented. Various LB film stacks were imaged to verify the intensity interpretation due to the exponentially decaying
evanescent fields of the waveguides. The paper gives an overview on the imaging applications of this technique. The
fluorescence intensity has been used to determine quantitatively the cell attachment of osteoblasts (bone forming cells)
to substrate surfaces. In live cell studies trypsin (a protease) was used to alter attachment of the cells to the substrate, as a
means to demonstrate feasibility of the method in measuring attachment dynamics of cells in real time.
Immobilized gold nanoparticles on oxide surfaces were prepared by template assisted organometallic chemical vapor deposition (OMCVD). The growth parameters, optical parameters such as the plasmon resonance band, as well as geometrical parameters such as size and shape are investigated by UV-Vis spectroscopy, AFM, TEM and SEM. These new kind of gold nanoparticles were applied on a fluorescence based oligonucleotide hybridization study. Gold nanoparticles with a mean lateral diameter of 12 nm yielding an extinction maximum at around 520-530 nm should be able to resonantly excite the Cy3-fluorescence label attached to the target oligonucleotide. The hybridization reaction is taking place between gold nanoparticle surface-attached oligonucleotide catcher strands and chromophore-labeled target strands in solution. The experiment was conducted in the form of classical total internal reflection fluorescence detection. The kinetic data were quantitatively analyzed following a simple Langmuir model. It was found that a single mismatch between oligonucleotide target and probe reduces the Langmuir equilibrium constant by two orders of magnitude, allowing for an excellent sequence-specific detection of oligonucleotide hybridization based on OMCVD gold nanoparticles.
Polymethylmetacrylate with covalently bound side-chain azo- benzene group is synthesized and thin films are fabricated. Holographic grating recording is achieved with a 442 nm He- Cd laser at three different grating spacing: 646, 1340 and 2220 nm. The dependence of the diffraction efficiency on time is investigated. The optical recording is stable for more than four years at room temperature. Optical erasure can be performed with circularly and linearly polarized laser light.
The coupling of p-polarized waveguide modes into waveguide- surface plasmon coupled modes is a promising concept to combine the features of propagating waveguide modes with the resonant field enhancement of surface plasmons. We demonstrate a waveguide device which allows to couple more than one TM mode to the surface plasmon. For a given waveguide device and a fixed laser wavelength the development of the imaginary part, K, of the propagation constant, Neff, of the waveguide-surface plasmon coupled modes are simulated and the results are compared with experimental results. The waveguide losses are in perfect agreement with the simulations. Due to the resonant nature of the waveguide-surface plasmon coupled modes, which was found by the simulations, the waveguide attenuation is very sensitive to the refractive index of the subphase outside of the waveguide structure. This resonant behavior could be confirmed experimentally.
Scattering optical waveguide microscopy is a novel imaging technique, that allows for the microscopic characterization of thin film samples by using the evanescent field of a guided optical wave as the illuminating light source. The image contrast is generated by the scattered intensity of the thin film sample within the evanescent field. Excellent lateral resolution (< 1 micrometers ) is demonstrated for an evaporated SiOx grating. Immersion microscopy has been performed with an additional cuvette in the same setup. The contrast of the image is investigated with respect to mode number and polarization of the illuminating, propagating waveguide mode and the surface roughness of the sample.
Photothermal beam deflection spectroscopy (PTBDS) is used together with waveguide loss measurements to distinguish between intrinsic, absorptive and scattering losses in polymeric waveguide materials. Overtones of vibrational modes of organic waveguide materials in the near infrared spectral regime can be distinguished very precisely with PTBDS. In an example of different polythiophens, we demonstrate the influence of the sidechains (CH2- and CH3-vibrations) and the conformation of the mainchain on the absorption spectrum in the spectral regime of optical telecommunications. The photothermal beam deflection method is also used for imaging waveguide structures and to investigate order parameters of dyes within a polymeric matrix.
We demonstrate a new method for investigating the orientational distribution of the rod-like poly[bis(m-butoxyphenyl) silane] molecules in Langmuir-Blodgett (LB) films. The first two non-trivial in-plane orientational order parameters C2 and C4 could be easily deduced by measuring the independent tensor components of (chi) (3)(-(omega) 3;(omega) 1,(omega) 1,(omega) 2). Using this method, we show that the annealing process improves the molecular alignment along the dipping direction. We were also able to get information about the domain morphology of the film from the off-diagonal components of (chi) (3).
We demonstrate resonant third harmonic generation as a powerful tool for analyzing the quasi 2-D molecular orientational order in a Langmuir-Blodgett film of poly(bis-m- butoxyphenylsilane). By recording Maker-fringes at different angles between the polarization of the fundamental beam and the dipping direction, we were able to determine the order parameters *2> and *4> simultaneously. We found *2> equals 0.466 +/- 0.030 and *4> equal to -0.12 +/- 0.10.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.