Approaches for Positioning the Active Medium in Hybrid Nanoplasmonics. Focus on Plasmon-Assisted Photopolymerization.

Over the past 20 years, hybrid plasmonics for nanoemitters of light or for nanoabsorbers, based on weak or strong coupling between metallic nanocavities and active media (emissive or absorbing entities), have given rise to important research efforts. One of the main current challenges is the control of the nanoscale spatial distribution and associated symmetry of the active medium in the vicinity of the metallic nanoparticles. In this review, we first recall the main principles of weak and strong coupling by stressing the importance of controlling the spatial distribution of the active medium and present the main approaches developed for achieving this control.

Boosting the Performances of Semitransparent Organic Photovoltaics via Synergetic Near-Infrared Light Management.

Semitransparent organic photovoltaics (ST-OPVs) offer promising prospects for application in building-integrated photovoltaic systems and greenhouses, but further improvement of their performance faces a delicate trade-off between the two competing indexes of power conversion efficiency (PCE) and average visible transmittance (AVT). Herein, the authors take advantage of coupling plasmonics with the optical design of ST-OPVs to enhance near-infrared absorption and hence simultaneously improve efficiency and visible transparency to the maximum extent. By integrating core-bishell PdCu@Au@SiO nanotripods that act as optically isotropic Lambertian sources with near-infrared-customized localized surface plasmon resonance in an optimal ternary PM6:BTP-eC9:L8-BO-based ST-OPV, it is shown that their interplay with a multilayer optical coupling layer, consisting of ZnS(130 nm)/NaAlF(60 nm)/WO(100 nm)/LaF(50 nm) identified from high-throughput optical screening, leads to a record-high PCE of 16.

Advanced active polymer probe for near-field optics.

We report on a novel, to the best of our knowledge, active probe for scanning near-field optical microscopy (SNOM). A fluorescent nanosphere, acting as the secondary source, is grafted in an electrostatic manner at the apex of a polymer tip integrated into the extremity of an optical fiber. Thanks to the high photostability and sensitivity of the secondary source, the near-field interaction with a gold nanocube is investigated.

Quantum Dot Transfer from the Organic Phase to Acrylic Monomers for the Controlled Integration of Single-Photon Sources by Photopolymerization.

This paper reports on a new strategy for obtaining homogeneous dispersion of grafted quantum dots (QDs) in a photopolymer matrix and their use for the integration of single-photon sources by two-photon polymerization (TPP) with nanoscale precision. The method is based on phase transfer of QDs from organic solvents to an acrylic matrix. The detailed protocol is described, and the corresponding mechanism is investigated and revealed.

Phase-resolved all-fiber reflection-based s-NSOM for on-chip characterization.

We report on a phase-resolved, reflection-based, scattering-type near-field scanning optical microscope technique with a convenient all-fiber configuration. Exploiting the flexible positioning of the near-field probe, our technique renders a heterodyne detection for phase measurement and point-to-point frequency-domain reflectometry for group index and loss measurement of waveguides on a chip. The important issue of mitigating the measurement errors due to environmental fluctuations along fiber-optic links has been addressed.

Highly Sensitive Plasmonic Biosensors with Precise Phase Singularity Coupling on the Metastructures.

In this paper, we demonstrated the ability of a plasmonic metasensor to detect ultra-low refractive index changes (in the order of ∆n = 10 RIU), using an innovative phase-change material, vanadium dioxide (VO), as the sensing layer. Different from current cumbersome plasmonic biosensing setups based on optical-phase-singularity measurement, our phase signal detection is based on the direct measurement of the phase-related lateral position shift (Goos-Hänchen) at the sensing interface. The high sensitivity (1.

Sensitivity Enhancement of Hybrid Two-Dimensional Nanomaterials-Based Surface Plasmon Resonance Biosensor.

In this work, we designed structures based on copper nanosubstrate with graphene and two-dimensional transition metal dichalcogenides (TMDC) in order to achieve an ultrasensitive surface plasmon resonance biosensor. This system contains seven components: SF11 triangular prism, BK-7 glass, Chromium (Cr) adhesion layer, thin copper film, layers of one of the types of transition metal dichalcogenides: MoS, MoSe, WS or WSe (defined as MX), graphene, sensing layer with biomolecular analyte. Copper was chosen as a plasmonic material because it has a higher conductivity than gold which is commonly used in plasmonic sensors.

High-Performance Semitransparent Organic Solar Cells: From Competing Indexes of Transparency and Efficiency Perspectives.

Semitransparent organic solar cells (ST-OSCs) offer potentially more opportunities in areas of self-powered greenhouses and building-integrated photovoltaic systems. In this work, the effort to use a combination of solution-processable gold nanobipyramids (AuNBPs)-based hole transporting layer and a low/high dielectric constant double layer optical coupling layer (OCL) for improving the performance of ST-OSCs over the two competing indexes of power conversion efficiency (PCE) and average visible transmittance (AVT) is reported. The fabrication and characterization of the ST-OSCs are guided, at design and analyses level, using the theoretical simulation and experimental optimization.

One Strategy for Nanoparticle Assembly onto 1D, 2D, and 3D Polymer Micro and Nanostructures.

The integration of nanoparticles (NPs) into photonic devices and plasmonic sensors requires selective patterning of these NPs with fine control of their size, shape, and spatial positioning. In this article, we report on a general strategy to pattern different types of NPs. This strategy involves the functionalization of photopolymers before their patterning by two-photon laser writing to fabricate micro- and nanostructures that selectively attract colloidal NPs with suitable ligands, allowing their precise immobilization and organization even within complex 3D structures.

Hybrid plasmonic nano-emitters with controlled single quantum emitter positioning on the local excitation field.

Hybrid plasmonic nano-emitters based on the combination of quantum dot emitters (QD) and plasmonic nanoantennas open up new perspectives in the control of light. However, precise positioning of any active medium at the nanoscale constitutes a challenge. Here, we report on the optimal overlap of antenna's near-field and active medium whose spatial distribution is controlled via a plasmon-triggered 2-photon polymerization of a photosensitive formulation containing QDs.

Hybrid nanostructured plasmonic electrodes for flexible organic light-emitting diodes.

Improved performance in flexible organic light-emitting diodes (OLEDs) is demonstrated by using a hybrid nanostructured plasmonic electrode consisting of silver nanowires (AgNWs) decorated with silver nanoparticles (AgNPs) and covered by exfoliated graphene sheets. Such all-solution processed electrodes show high optical transparency and electrical conductivity. When integrated in an OLED with super yellow polyphenylene vinylene as the emissive layer, the plasmon coupling of the NW-NP hybrid plasmonic system is found to significantly enhance the fluorescence, demonstrated by both simulations and photoluminescence measurements, leading to a current efficiency of 11.

Local Optical Chirality Induced by Near-Field Mode Interference in Achiral Plasmonic Metamolecules.

When circularly polarized light interacts with a nanostructure, the optical response depends on the geometry of the structure. If the nanostructure is chiral (i.e.

Imaging of guided waves using an all-fiber reflection-based NSOM with self-compensation of a phase drift.

A phase-resolved reflection-based near-field scanning optical microscopy (NSOM) technique with an original all-fiber configuration is presented. Our system consists of an intrinsically phase-stable common-path interferometer. The reflection from the waveguide input facet or from an integrated fiber Bragg grating is used as the reference beam.

Full control of far-field radiation via photonic integrated circuits decorated with plasmonic nanoantennas.

We theoretically develop a hybrid architecture consisting of photonic integrated circuit and plasmonic nanoantennas to fully control optical far-field radiation with unprecedented flexibility. By exploiting asymmetric and lateral excitation from silicon waveguides, single gold nanorod and cascaded nanorod pair can function as component radiation pixels, featured by full 2π phase coverage and nanoscale footprint. These radiation pixels allow us to design scalable on-chip devices in a wavefront engineering fashion.

Plasmon-emitter interaction using integrated ring grating-nanoantenna structures.

Overcoming the diffraction limit to achieve high optical resolution is one of the main challenges in the fields of plasmonics, nanooptics and nanophotonics. In this work, we introduce novel plasmonic structures consisting of nanoantennas (nanoprisms, single bowtie nanoantennas and double bowtie nanoantennas) integrated in the center of ring diffraction gratings. Propagating surface plasmon polaritons (SPPs) are generated by the ring grating and coupled with localized surface plasmons (LSPs) at the nanoantennas exciting emitters placed in their gap.

Two-Color Single Hybrid Plasmonic Nanoemitters with Real Time Switchable Dominant Emission Wavelength.

We demonstrate two-color nanoemitters that enable the selection of the dominant emitting wavelength by varying the polarization of excitation light. The nanoemitters were fabricated via surface plasmon-triggered two-photon polymerization. By using two polymerizable solutions with different quantum dots, emitters of different colors can be positioned selectively in different orientations in the close vicinity of the metal nanoparticles.

Rapid fabrication of micro-nanometric tapered fiber lens and characterization by a novel scanning optical microscope with submicron resolution.

In numerous applications of optical scanning microscopy, a reference tapered fiber lens with high symmetry at sub-wavelength scale remains a challenge. Here, we demonstrate the ability to manufacture it with a wide range of geometry control, either for the length from several hundred nanometers to several hundred microns, or for the curvature radius from several tens of nanometers to several microns on the endface of a single mode fiber. On this basis, a scanning optical microscope has been developed, which allows for fast characterization of various sub-wavelength tapered fiber lenses.

Optimizing Electromagnetic Hotspots in Plasmonic Bowtie Nanoantennae.

Sensitivity is a key factor in the improvement of nanoparticle-based biosensors. Bowtie nanoantennae have shown high sensitivity for both surface-enhanced Raman scattering (SERS)- and localized surface plasmon resonance (LSPR)-based biosensing. In this work, optical bowtie nanoantennae with varying geometries were simulated, fabricated, and characterized.

Reversible strong coupling in silver nanoparticle arrays using photochromic molecules.

In this Letter, we demonstrate a reversible strong coupling regime between a dipolar surface plasmon resonance and a molecular excited state. This reversible state is experimentally observed on silver nanoparticle arrays embedded in a polymer film containing photochromic molecules. Extinction measurements reveal a clear Rabi splitting of 294 meV, corresponding to ~13% of the molecular transition energy.

Spatial confinement of electromagnetic hot and cold spots in gold nanocubes.

We report a near-field imaging study of colloidal gold nanocubes. This is accomplished through a photochemical imaging method in which molecular displacements are vectorial in nature, enabling sensitivity to the polarization of the optical near-field of the nanocubes. We analyze the confinement of both electromagnetic hot and "cold" spots with a resolution of λ/35 and emphasize the particularly high spatial confinement of cold spots.

Plasmon-based free-radical photopolymerization: effect of diffusion on nanolithography processes.

This Article interrogates the mechanisms responsible for nanoscale photopolymerization induced by confined and enhanced electromagnetic fields. Surface plasmon dipolar resonance of individual Ag nanoparticles was used as an optical near-field source to locally trigger the reaction of a photopolymerizable formulation. Laser excitation of the nanoparticles embedded in the formulation reproducibly generates polymer features with typical dimensions ranging from 2 nm to a few tens of nanometer.

Integration of polymer microlens array at fiber bundle extremity by photopolymerization.

We present a novel route to directly integrate an array of microlenses at the extremity of an optical fiber bundle. The method is based on photopolymerization at the end of the fiber. The method is based on the control of exposure dose and volume of the deposited droplet of photopolymerizable formulation.

Off-Resonant Optical Excitation of Gold Nanorods: Nanoscale Imprint of Polarization Surface Charge Distribution.

We report on the nanoscale optical characterization of gold nanorods irradiated out of their plasmonic resonance. Our approach is based on the reticulation of a photopolymerizable formulation locally triggered by enhanced electromagnetic fields. The tiny local field enhancement stems from the surface polarization charges associated with the electric field discontinuity at the metal/dielectric interface.

Biopolymers phase separation monitored by a plasmonic sensor.

We report here a real-time study of interactions induced phase separation between β-lactoglobulin (BLG) and Acacia gum (AG) by analyzing the localized surface plasmon resonance of silver nanoparticles. We showed that the binding of BLG to AG is accompanied by refractive index changes, in relation with optical properties and structural changes of the complexes formed.

Quantitative analysis of localized surface plasmons based on molecular probing.

We report on the quantitative characterization of the plasmonic optical near-field of a single silver nanoparticle. Our approach relies on nanoscale molecular molding of the confined electromagnetic field by photoactivated molecules. We were able to directly image the dipolar profile of the near-field distribution with a resolution better than 10 nm and to quantify the near-field depth and its enhancement factor.