Irene Fernandez-Cuesta

Plasmonic V-groove waveguides with Bragg grating filters via nanoimprint lithography

We demonstrate spectral filtering with state-of-the-art Bragg gratings in plasmonic V-groove waveguides fabricated by wafer scale processing based on nanoimprint lithography. Transmission spectra of the devices having 16 grating periods exhibit spectral rejection of the channel plasmon polaritons with 8.2 dB extinction ratio and -3 dB bandwidth of Δλ = 39.9 nm near telecommunications wavelengths. Near-field scanning optical microscopy measurements verify spectral reflection from the grating structures, and the oscillations of propagating modes along grating-less V-grooves correspond well with effective refractive index values calculated by finite element simulations in COMSOL. The results represent advancement towards the implementation of plasmonic V-grooves with greater functional complexity and mass-production compatibility.

Channel plasmon polariton propagation in nanoimprinted V-groove waveguides

We present the results of optical characterization of metal V-groove waveguides using scanning near-field microscopy, showing broadband transmission with subwavelength confinement and propagation lengths exceeding 100 microm. An updated fabrication method using a combination of UV and nanoimprint lithography is presented. The developed approach is mass-production compatible, adaptable to different designs, and offers wafer-scale parallel fabrication of plasmonic components based on profiled metal surfaces.

V-groove plasmonic waveguides fabricated by nanoimprint lithography

Propagation of channel plasmon-polariton modes in the bottom of a metal V groove has been recently demonstrated. It provides a unique way of manipulating light at nanometer length scale. In this work, we present a method based on nanoimprint lithography that allows parallel fabrication of integrated optical devices composed of metal V grooves. This method represents an improvement with respect to previous works, where the V grooves were fabricated by direct milling of the metal, in terms of robustness and throughput.

Atomic force microscopy local anodic oxidation of thin Si3N4 layers for robust prototyping of nanostructures

Local anodic oxidation by atomic force microscopy (AFM) of thin silicon nitride layers deposited on silicon wafers allows the definition of stamps for nanoimprint lithography. The study of the mechanism and kinetics of the AFM induced oxidation shows that the patterns on silicon nitride can be generated faster and at lower voltages than directly on silicon surfaces. Stamp fabrication is completed by chemical wet etching of the samples after the AFM patterning, resulting in a robust process because of the excellent properties of silicon nitride as a mask for selective wet etching. As a demonstrator, a stamp for nanoimprint lithography is fabricated that will be used for the realization of biosensors based on interdigitated nanoelectrodes.

Protein patterning on the micro- and nanoscale by thermal nanoimprint lithography on a new functionalized copolymer

The localized depositions such as DNA or proteins at the micron or submicron scale on solids supports are a crucial step in the fabrication of advanced biochips and laboratory on chip devices. The present work shows a new approach: A new biofunctionalized copolymer based on 80% benzyl methacrylate and 20% succinimydil methacrylate is used as a printable polymer with a great affinity to proteins, leading to combined areas covered by proteins and areas with resistance to protein adsorption in the submicron scale. Based on this approximation, an immunoassay is proposed as a proof of concept to detect the presence of the rabbit IgG protein up to concentrations of 200 ng/ml.

Excitation of fluorescent nanoparticles by channel plasmon polaritons propagating in V-grooves

Recently, it has been proven that light can be squeezed into metallic channels with subwavelength lateral dimensions. Here, we present the study of the propagation of channel plasmon polaritons confined in gold V-grooves, filled with fluorescent particles. In this way, channel plasmon polaritons propagating in nonempty V-grooves can be characterized, as the propagation track can be directly visualized in the microscope. We have found that beads with subwavelength diameters act as frequency converters for the propagating channel modes, resulting in larger propagation lengths. For micrometric-diameter beads, we show the possibility of individual excitation, what may have applications to develop very sensitive biosensors.

Fabrication of ordered arrays of quantum wires through hole patterning

We present empirical tight-binding calculations of the electronic structure of an array of mechanically connected silicon nanopillars. Structural parameters are chosen so that electrons are confined within each pillar, obtaining an array of effectively decoupled one-dimensional states. We address fabrication issues and present results demonstrating the suitability of the process.

Fabrication of plasmonic waveguides for device applications

We report on experimental realization of different metal-insulator geometries that are used as plasmonic waveguides guiding electromagnetic radiation along metal-dielectric interfaces via excitation of surface plasmon polaritons (SPPs). Three configurations are considered: metal strips, symmetric nanowires and nanowire pairs embedded in a dielectric, and metal V-shaped grooves. Planar plasmonic waveguides based on nm-thin and μm-wide gold strips embedded in a polymer that support propagation of long-range SPPs are shown to constitute an alternative for integrated optical circuits. Using uniform and thickness-modulated gold strips different waveguide components including reflecting gratings can be realized. For applications where polarization is random or changing, metal nanowire waveguides are shown to be suitable candidates for efficient guiding of arbitrary polarized light. Plasmonic waveguides based on metal V-grooves that offer subwavelength confinement are also considered. We focus on recent advances in manufacturing of nanostructured metal strips and metal V-grooves using combined UV, electron-beam and nanoimprint lithography.

Bragg grating filters in plasmonic V-groove waveguides

We demonstrate spectral filtering via Bragg gratings in plasmonic V-groove waveguides. Transmission spectra of wafer-scale fabricated devices exhibit 8.2 dB extinction ratio with 39.9 nm bandwidth. Near-field measurements verify spectral rejection.

Gratings in plasmonic V-groove waveguides

We introduce visible light optical gratings to surface plasmon V-groove waveguides. Gradient e-beam dosage onto silicon stamp enables structuring V-grooves of varying depth. Nanoimprint lithography maintains a Λ=265 nm corrugation for gold surface devices.