evaluating-plasmonic-transport-in-current-carrying-silver-nanowires

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information ...

Université de Bourgogne

Measuring the thickness of biological films remains a difficult task when using differential measurements by atomic force microscopy (AFM). The use of microstructured substrates combined with a selective adsorption constitutes an alternative to tribological measurements. The statistical thickness analysis of biological layers, especially via the dispersion measurements, can provide a way to quantify the molecular orientation. AFM thicknesses were then compared with those obtained optically by spectroscopic ellipsometry (SE) and surface plasmon resonance enhanced ellipsometry (SPREE). The biolayers could then be modeled using a vertical gradient of optical index, which reflects height dispersions. Thiol-modified DNA strands of various lengths account for a good biological model for the study of the strand motion in air and in liquid.

Measurements of thickness dispersion in biolayers by scanning force microscopy and comparison with spectroscopic ellipsometry analysis.

The design, fabrication, characterization, and modeling of basic building blocks of plasmonic circuitry based on dielectric-loaded surface polariton waveguides, such as bends, splitters, and Mach-Zehnder interferometers are presented. The plasmonic components are realized by depositing subwavelength dielectric ridges on a smooth gold film using mass-production-compatible UV-photolithography. The near-field characterization at telecommunication wavelengths shows the strong mode confinement and low radiation and bend losses. The performance of the devices is found in good agreement with results obtained by full vectorial three-dimensional finite element simulations.

Bend- and splitting loss of dielectric-loaded surface plasmon-polariton waveguides.

We consider wavelength-selective splitting of radiation using directional couplers (DCs) formed by dielectric-loaded surface-plasmon-polariton waveguides (DLSPPWs). The DCs were fabricated by depositing sub-wavelength-sized polymer ridges on a gold film using large-scale UV photolithography and characterized at telecommunications wavelengths with near-field microscopy. We demonstrate a DLSPPW-based 45-microm-long DC comprising 3 microm offset S bends and 25-microm-long parallel waveguides that changes from the "through" state at 1500 nm to 3 dB splitting at 1600 nm, and show that a 50.5-microm-long DC should enable complete separation of the radiation channels at 1400 and 1620 nm. The DC performance is found to be in good agreement with full vectorial three-dimensional finite-element simulations.

Wavelength-selective directional coupling with dielectric-loaded plasmonic waveguides.

Using near-field microscopy, the performance of dielectric-loaded plasmonic waveguide-ring resonators (WRRs) operating at telecom wavelengths is investigated for various waveguide-ring separations. It is demonstrated that compact (footprint approximately 150 microm(2)) and efficient (extinction ratio approximately 13 dB) WRR-based filters can be realized using UV-lithography. The WRR wavelength responses measured and calculated using the effective-index method are found in good agreement.

Dielectric-loaded plasmonic waveguide-ring resonators.

The spatial confinement of surface plasmon polaritons is a promising route for realizing optical on-board interconnects. However, mode losses increase with the confinement factor. To overcome this road block, we investigate propagation assisted by stimulated emission in a polymer strip-loaded plasmonic waveguide doped with nanocrystals. We achieve 27% increase of the propagation length at telecom wavelength corresponding to a 160 cm(-1) optical gain coefficient. Such a configuration is a step toward integrated plasmonic amplifiers.

Gain-assisted propagation in a plasmonic waveguide at telecom wavelength.

We report preliminary results on the development of compact (length < 100 microm) fiber-coupled dielectric-loaded plasmonic waveguide components, including Mach-Zehnder interferometers (MZIs), waveguide-ring resonators (WRRs) and directional couplers (DCs), whose operation at telecom wavelengths is controlled via the thermo-optic effect by electrically heating the gold stripes of dielectric-loaded plasmonic waveguides. Strong output modulation (> 20%) is demonstrated with MZI- and WRR-based components, and efficient (approximately 30%) rerouting is achieved with DC switches.

Thermo-optic control of dielectric-loaded plasmonic waveguide components.

Fiber in- and out-coupling of radiation guided by dielectric-loaded surface plasmon-polariton waveguides (DLSPPWs) is realized using intermediate tapered dielectric waveguides. The waveguide structures fabricated by large-scale UV-lithography consist of 1-microm-thick polymer ridges tapered from 10-microm-wide ridges deposited directly on a magnesium fluoride substrate to 1-microm-wide ridges placed on a 50-nm-thick and 100-microm-wide gold stripe. Using fiber-to-fiber transmission measurements at telecom wavelengths, the performance of straight and bent DLSPPWs is characterized demonstrating the overall insertion loss below 24 dB, half of which is attributed to the DLSPPW loss of propagation over the 100-microm-long distance.

Fiber-coupled dielectric-loaded plasmonic waveguides.

In the present work, the combination of chemical immobilization with electron beam lithography enables the production of sensitive and reproducible SERS-active areas composed of stochastic arrangements of gold nanoparticles. The number of nanoparticles was varied from 2 to 500. Thereby a systematic analysis of these SERS-active areas allows us to study SERS efficiency as a function of the number of nanoparticles. We found that the experimental parameters are critical, in particular the size of the SERS-active area must be comparable to the effective area of excitation to obtained reproducible SERS measurements. The sensitivity has also been studied by deducing the number of NPs that generate the enhancement. With this approach we demonstrates that the maximum enhancement, the best sensitivity, is obtained with the smallest number of nanoparticles that is resonant at a given excitation wavelength.

Influence of the number of nanoparticles on the enhancement properties of surface-enhanced Raman scattering active area: sensitivity versus repeatability.

We report on propagating mode power monitoring in dielectric-loaded surface plasmon-polariton waveguides (DLSPPWs) by measuring the resistance of gold stripes supporting the DLSPPW mode propagation. Inevitable absorption of the DLSPPW mode in metal causes an increase in the stripe temperature and, thereby, in its resistance whose variations are monitored with an external Wheatstone bridge being accurately balanced in the absence of radiation in a waveguide. The investigated waveguide configuration consists of a 1-µm-thick and 10-µm-wide polymer ridges tapered laterally to a 1-µm-wide ridge placed on a 50-nm-thin and 4-µm-wide gold stripe, all supported by a magnesium fluoride substrate. Using single-mode polarization-maintaining fiber for in- and out-coupling of radiation, DLSPPW mode power monitoring at telecom wavelengths is realized with the responsivities of up to ~1.8 µV/µW (showing weak wavelength dependence) being evaluated for a bias voltage of 1 V.

Power monitoring in dielectric-loaded surface plasmon-polariton waveguides.

We demonstrate optical fiber-pigtailed temperature sensors based on dielectric-loaded surface plasmon-polariton waveguide-ring resonators (DLSPP-WRRs), whose transmission depends on the ambient temperature. The DLSPP-WRR-based temperature sensors represent polymer ridge waveguides (~1×1 µm(2) in cross section) forming 5-µm-radius rings coupled to straight waveguides fabricated by UV-lithography on a 50-nm-thick gold layer atop a 2.3-µm-thick CYTOP layer covering a Si wafer. A broadband light source is used to characterize the DLSPP-WRR wavelength-dependent transmission in the range of 1480-1600 nm and to select the DLSPP-WRR component for temperature sensing. In- and out-coupling single-mode optical fibers are then glued to the corresponding access (photonic) waveguides made of 10-µm-wide polymer ridges. The sample is heated from 21°C to 46 °C resulting in the transmission change of ~0.7 dB at the operation wavelength of ~1510 nm. The minimum detectable temperature change is estimated to be ~5.1∙10(-3) °C for the bandwidth of 1 Hz when using standard commercial optical detectors.

Fiber-pigtailed temperature sensors based on dielectric-loaded plasmonic waveguide-ring resonators.

With metal stripes being intrinsic components of plasmonic waveguides, plasmonics provides a "naturally" energy-efficient platform for merging broadband optical links with intelligent electronic processing, instigating a great promise for low-power and small-footprint active functional circuitry. The first active Dielectric-Loaded Surface Plasmon Polariton (DLSPP) thermo-optic (TO) switches with successful performance in single-channel 10 Gb/s data traffic environments have led the inroad towards bringing low-power active plasmonics in practical traffic applications. In this article, we introduce active plasmonics into Wavelength Division Multiplexed (WDM) switching applications, using the smallest TO DLSPP-based Mach-Zehnder interferometric switch reported so far and showing its successful performance in 4×10 Gb/s low-power and fast switching operation. The demonstration of the WDM-enabling characteristics of active plasmonic circuits with an ultra-low power × response time product represents a crucial milestone in the development of active plasmonics towards real telecom and datacom applications, where low-energy and fast TO operation with small-size circuitry is targeted.

Active plasmonics in WDM traffic switching applications.

We report detailed experimental studies of compact fiber-coupled dielectric-loaded plasmonic waveguide components-Mach-Zehnder interferometers (MZIs) and directional couplers (DCs)-whose operation at telecom wavelengths is controlled via the thermo-optic effect by electrically heating the gold stripe of dielectric-loaded plasmonic waveguides. The effect of the gaps isolating the heated part of the waveguide from the rest of the structure was examined showing the presence of a Fabry-Pérot cavity in this MZI arm. Wavelength-dependent modulation is demonstrated with MZI-based components, and wavelength dependent low power (∼0.92 mW) rerouting is achieved with DC switches. Furthermore, simulations were performed to confirm the switching characteristics of the components.

Thermo-optic control of dielectric-loaded plasmonic Mach-Zehnder interferometers and directional coupler switches.

Pulmonary surfactant is a complex mixture of phospholipids and proteins and forms a thin film at the lung alveolar interface separating air from liquid environment. The film reduces the work of breathing during repeatable compressions of the alveoli which form a characteristic multilayer upon compression. In this work, we investigated the structure of bovine lipid extract surfactant (BLES). We analysed the BLES films by atomic force microscopy (AFM) and spectroscopic ellipsometry (SE) in order to provide combined characterization of both morphology and thickness of surfactant films. We show how the spectroscopic ellipsometry can be used to supplement the data obtained by AFM. We demonstrate that indium tin oxide (ITO) substrate used for spectroscopic ellipsometry is preferable over glass substrate to enhance the optical contrast. An optical model was proposed to account for non-uniform film morphology. We obtained good correlations between the multilayer surface coverage, determined by both AFM and SE. SE measures the thickness of the first uniform monolayer as 2.6 nm that cannot be achieved by AFM imaging alone.

Combined atomic force microscopy and spectroscopic ellipsometry applied to the analysis of lipid-protein thin films.

We report on monitoring the mode power in dielectric-loaded surface plasmon polariton waveguides (DLSPPWs) by measuring the resistance of gold electrodes, supporting the DLSPPW mode propagation, with internal (on-chip) Wheatstone bridges. The investigated DLSPPW configuration consisted of 1-μm-thick and 10-μm-wide cycloaliphatic acrylate polymer ridges tapered laterally to a 1-μm-wide ridge placed on a 50-nm-thin and 4-um wide gold stripe, all supported by a ~1.7-µm-thick Cytop layer deposited on a Si wafer. The fabricated DLSPPW power monitors were characterized at telecom wavelengths, showing very high responsivities reaching up to ~6.4 μV/μW (for a bias voltage of 245 mV) and the operation bandwidth exceeding 40 kHz.

Laurent Markey

Laboratoire Interdisciplinaire Carnot de Bourgogne CNRS-UMR 6303

Université de Bourgogne

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Laurent Markey

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Laboratoire Interdisciplinaire Carnot de Bourgogne CNRS-UMR 6303

Université de Bourgogne

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Laboratoire Interdisciplinaire Carnot de Bourgogne CNRS-UMR 6303