This PDF file contains the front matter associated with SPIE Proceedings Volume 12131, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

One of the most powerful technologies for single molecule fluorescence spectroscopy at concentrations which are close to biological processes (micro and millimolar) is based on the use of Zero Mode Waveguides (ZMWs). Standard ZMWs are prepared as nanoholes array in Al thin films. Although very efficient to enable single molecule detection, Al-ZMWs are not optimized in term of fluorescence emission. On the contrary an engineered configuration where alternative metals such as Au, Ag, Al, etc. are used can produce significant enhancement in the single molecule detection. Thanks to optimized designs can be possible to enhance the fluorescence emission not only in the visible spectral range but also in the Ultraviolet (UV) and Near-infrared (NIR). Here we discuss the major results on plasmonic ZMWs and their use in single molecule fluorescence.

In this work, the effect of roughness on surface plasmon propagation along metallic gratings is investigated. In the case of a shallow sinusoidal grating, modeling that takes into account the surface roughness shows the modification of the coupling properties of the plasmon modes. In the case of a deep sinusoidal rough grating, modeling of the SPR response is compared to the experimental one, showing a strengthening of the intra-coupling between forward and backward plasmon modes. This study demonstrates that the effect of the surface roughness on plasmon propagation must be considered especially in the case of deep gratings.

Cu_2-xS nanoparticles have the ability to absorb radiation in the near infrared (NIR) range. This is due to localized surface plasmon resonance (LSPR) of free holes in the valence band. This fact makes it possible to use copper sulfide nanoparticles for sensing application in the NIR range. Our study showed that Cu_2-xS nanoparticles have a significant localized surface plasmon resonance. The LSPR of nanoparticles was tuned by adjusting the concentrations of Cu and S. In this case, the plasmon peak reaches a maximum at values of about 1210 nm. Thus, highly localized electromagnetic field of Cu_2-xS NPs can be successfully applied for to detection of vibrational bands (overtones) of various molecules in the NIR region. We showed the splitting of longitudinal and transverse dipolar resonance modes of Cu_1.4S was changed in the presence of NMethylamine molecules.

Plasmonic nanoantennas mediate far and near optical fields and confine the light to subwavelength dimensions. Directional plasmonic antennas increase the emission and collection efficiency of optical networks. To obtain directionality, the spatial organization of nanoantenna elements is critical as it affects the interelement coupling and determines the resultant antenna mode. Moreover, to drive the antenna from its near field, near-field sources such as quantum emitters are required and their distance with respect to antenna elements is the main determinant in coupling between the main antenna mode and the emitter. To couple quantum emitters to optical antennas, high precision on the order of a few nm with respect to the antenna is necessary. As an emerging nanofabrication technique, DNA origami has proven itself to be a robust nanobreadboard to obtain sub-5 nm positioning precision for a diverse range of materials. Here, we use DNA origami to assemble a nanoantenna composed of three gold nanoparticles with sub-5 nm interparticle gaps to break the symmetry and scatter light in one direction very strongly compared to the rest of the directions. To drive this antenna, we place a single emitter, Atto647N dye molecule, exactly at one of the hotspots of the trimer. Here we present the first time realization of a unidirectional plasmonic nanoantenna driven by a single quantum emitter assembled by DNA origami.

In our work we focused femtosecond laser pulses in the infrared region onto conducting indium-tin-oxide (ITO) thin films. We observed laser induced periodic surface structures (LIPSS) with increasing periodicity close to λ/10 scaling. We conducted supporting finite-difference time-domain calculations to investigate the origin of these morphologies. The results suggest that the surface forms are rooted in the field localization in the surface pits leading to a periodically increased absorption of the laser pulse energy that creates the observed periodic structures.

This study was aimed to investigate the growth process of thin films on a pre-structured surface using different optically transparent materials and their optical properties. As results of conformal deposition of ion beam sputtered dense single layers on nano-modulated surfaces showed, replicability of surface modulation depends on the layer’s material itself. Among investigated metal oxides, namely tantalum, niobium, hafnium, and silicon oxides, materials with higher molecular weight tend to better repeatability of the initial structure. As an example, the surface modulation depth of tantalum oxide single layer of ~1 μm thickness has preserved almost 97 % of the initial structure, while the silica layer showed the most rapid smoothening of modulation since preserved only ~ 65 %. Considering that tantalum oxide single layers showed the best replicability results, its optical properties were investigated in a more detailed way. Optical characterization revealed the presence of Fano-like resonance phenomenon in such single-layer structure with high refractive index, surrounded by a lower refractive index media. Due to the coupling of thin film's waveguided modes with excited Fabry-Perot modes this phenomenon results in extremely low transmittance lines in the transmittance maps in a plane of the angle of incidence θ and wavelength λ. Moreover, these resonance lines show sensitivity to the angle and the wavelength of the incident light, which can serve as a demonstration of spatial and spectral filtering properties in such compact photonic single-layer structures.

The second harmonic generation in gold nanoprisms is investigated numerically and experimentally. Comparing the experimentally obtained cartographic SHG maps with numerically simulated maps, we are able to discriminate between the different nonlinear source contributions as well as demonstrate the response that dominates in these nanostructures. Precisely, we show that the parallel surface current source dominates in these nanoprisms which has been a largely discarded source in the literature.

In this work, we investigate silicon nanocavities to increase brightness and control directivity pattern in the near-IR wavelength range. Designed nanocavities consist of the silicon nanocylinder with Mie magnetic dipole resonance. Theoretically we predict that the Purcell factor can be enhanced by up to three orders of magnitude and consider directivity patterns. We use electron lithography and laser annealing methods to fabricate nanostructures. Experimentally, photoluminescence spectra are measured and demonstrated. We believe that results of this work can find its application in optical telecommunication systems.

Metal nanoparticles have been very active research object due to the local surface plasmon resonance effect that can be used in various applications, such as sensors, photovoltaic and Raman spectroscopy. Metallic nanoparticles enhanced fluorescence is an important effect to improve the emission properties of the semiconductor. It offers higher emission efficiency and decreased lifetime via the local electric field enhancement effect of metal nanoparticles induced by its surface plasmon resonance. Initially, inorganic semiconductors were used to show the emission enhancement, but recently more systems consist of organic semiconductors. It is driven by the growing potential of organic materials in the light-emitting diodes, photovoltaics, and solid-state lasers. Synthesis of specific size and shape of nanoparticles is important because it determines the spectrum of surface plasmon resonance which in turn should match the emission spectrum of an organic dye to get the highest enhancement. Silver nanoparticles typically are synthesized in aqueous solution and their transfer to organic solvents is required for application purposes in organic luminophores emission intensity enhancement. We studied prismatic and spherical silver nanoparticles transfer from aqueous to organic media by ultrasonic treatment and shell changing processes. Photoluminescence properties – emission maps, photoluminescence quantum yield and lifetime of obtained nanoparticles solutions mixtures with organic luminophore DWK-1-TB (2-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-4-ylidene)malononitrile) were studied. Improvements of photoluminescence properties was observed in nanoparticles based organic luminophore solutions. Presence of nanoparticles increased emission intensity, improved photoluminescence quantum yield and shifted excitation wavelength.

Our work demonstrates nonadiabatic tunneling of photoelectrons in the near-field of gold nanostructures, which occurs in the transition region between the multi-photon-induced photoemission and tunneling emission regimes. Measured kinetic energy spectra at higher laser intensities indicates strong-field electron accelaration and recollision, characteristic for the tunneling emission regime. At the same time, constant scaling of the photoelectron current with the intensity has been measured, a trait of the multi-photon-induced photoemission regime. The Keldysh value of γ ≈ 2 for the transition was determined by analyzing the measured photoemission spectra. This value is in good agreement with the results acquired by the numerical solution of the Time-Dependent Schrödinger Equation.

In this work, we introduce a spatial filtering mechanism that can be effectively utilized by photonic crystals. The phenomenon utterly expressed here is Rayleigh-Wood’s anomaly. Such a mechanism is realized and optimized via RCWA (Rigorous Coupled Wave Analysis) together with a global optimization algorithm for both s and p polarized inputs. The calculated transmission and reflection spectra of such mechanisms show that the Rayleigh anomaly provides the necessary sharp transmission profile near the critical wavelength from which the diffraction can occur.

We investigate the connection between losses of a guided mode and polarisation of the associated evanescent waves in the Poincaré sphere, demonstrating a ``polarization-loss locking'' in analogy to spin-momentum locking. From Fermi's golden rule, we investigate its implications for near-field directional coupling, via the introduction of a complex angular spectrum formalism. The use of complex wave-vector in the spectrum inspired us to investigate a method of achieving improved transmission of light across optically opaque materials by introducing a passive metasurface with a varying transmission phase and amplitude simultaneously.

In this work we highlight enantioselective optical gradient forces acting on Rayleigh-seized chiral particles present in 3D structured (non-paraxial) optical vortex tweezing systems. One discriminatory force originates from the circular polarization of the light and is similar to previous chiral optical gradient trapping forces. Much more remarkable is the other which is independent of the input beam’s polarization state - even occurring for unpolarized light – and is not present in 2D structured light nor propagating plane waves. This latter chiral sorting mechanism allows for the enantioselective trapping of chiral particles into distinct rings in the transverse plane through conservative radial forces.

One of the key trends in laser material processing is the usage of structured laser beams. One such example is the Bessel beam with an elongated focal area and self-healing properties. Higher-order Bessel beams can be formed by axicons, spiral phase plates, or equivalently by the phase masks (holograms). In this work, a demonstration of “optical drill” beams with dynamic intensity distributions resembling the spinning mechanical drill is shown. Bessel beam mixing of two different helicities is achieved by using a Spatial Light Modulator (SLM). Both Bessel beams are formed on the same optical component – the phase mask consisting of two parts. Each part consists of spirals with different winding numbers and different periods that correspond to different step plates and axicons. Such a mask forms the stationary optical drill beam. As the beam propagates the outer and inner parts start to overlap and form the resultant interfering beam. Now, to make it a true drill, it must rotate in time. In our experiment, that is achieved by rotating one part of the combined hologram. This induces an angular offset to the interference and as a result, the orientation of the helical intensity pattern starts to rotate in time. This continuous motion gives the impression of an optical drill. With the beams dynamic properties, it could become a new tool in laser material micromachining, as a mechanical drill was to construction.

Understanding the time-dependent states of plasmonic metasurfaces under intense laser irradiation is crucial to optimize the laser processing parameters and reach specific optical properties. In this work, the physico-chemical mechanisms of laser-induced shape transformation of Ag nanoparticle ensemble embedded in thin TiO₂ layers is investigated in details. The combination of high-repetition-rate pump-probe microscopy in transmission configuration with ex situ scanning electron microscopy reveals the variety of mechanisms that contribute to the reshaping of near-coalescence Ag nanoparticles with broad size and complex shape distributions into an ensemble of spherical particles. The description of the mechanisms on multiple time scales from the ultrafast electron dynamics to the much slower thermal processes triggered by the accumulation of 800 pulses at high repetition rate reveals different pulse number regimes. Owing to the high-repetition-rate data acquisition, the effect of the heat accumulation on the nanoparticle reshaping kinetics is demonstrated. The observed structural changes are discussed in the scope of the in situ transmission spectra. The presented results are intended to help improving applications of such laser-processed plasmonic metasurfaces in security printing, data storage and digital fabrication of nanoscale electronics.

We introduce our multi-coincidence setup used to study the interaction of highly charged ions with atomically thin materials. Ions are transmitted through freestanding two-dimensional materials and detected charge separated on a position sensitive microchannel plate detector with delay line anode. Electrons emitted upon the interaction of the projectile with the target can be detected either using a silicon surface barrier detector or a hemispherical analyser in order to gain information on the number of emitted electrons and their energy distribution, respectively. All data is stored in a listmode file allowing to set filters (e.g., time of flight, charge states) post measurement to identify the origin of correlated ion-electron pairs, i.e. we can determine whether detected ions were transmitted solely through the two-dimensional material layer or through its support structure. Using this coincidence technique we can correlate specific charge exchange and ion stopping channels (i.e. energy deposition) with particular electron emission scenarios (yield and energy distribution).

Composites based on nanomaterials are becoming more popular, especially for the creation of Förster Resonant Energy Transfer systems. Here, well-established zinc oxide tetrapods and a new carbon dot material were used to create a hybrid composite. The influence of the alkalinity of the medium on the formation of the composite was studied. The morphology and optical properties were studied in detail to confirm the formation of the composite. The measurement of photoluminescence lifetimes of carbon dots/zinc oxide tetrapods composites demonstrated nonradiative energy transfer. The efficiency of Förster Resonant Energy Transfer was theoretically calculated and the rate constants of this process, as well as reabsorption, were found. Consequently, the new composite based on carbon dots and zinc oxide tetrapods can find many applications, for example, in optical sensors.

The development of nanoparticle-based applications relies increasingly on our ability to characterize nanoparticles at the single-particle level and in their native liquid environment. In quantum dot applications, for example, a detailed understanding of how spectral properties are related to differences in size, shape, composition and electrical charge is crucial to optimize the fabrication process of quantum dots and ultimately their photonic or biomedical applications. Since deposition on a substrate may disturb the spectroscopic response it is preferred that measurements occur in the liquid phase. Sufficiently fast imaging is needed for measurements of the electrical charge and particle size. In the present work, we focus on measuring the electrophoretic mobility and size of individual nanoparticles in their native liquid environment through sensitive imaging at frame rates up to 10 kHz in the presence of an electric field. The particles of interest are fluorescently labelled polystyrene particles in the range of 40 nm to 100 nm. The imaging method is based on scanning a focused laser beam (532 nm) across a 10 µm x 10 µm field using acousto-optic deflectors and by detecting the emitted fluorescent light with a single-photon counter. The particle size is determined from Brownian motion analysis. The electrophoretic mobility and the electroosmotic mobility related to the zeta-potential of the microchannel walls are determined through analysis of the response at different frequencies of the applied electric field and at different positions in the microfluidic channel.

Magneto-luminescent nanocomposites can be used as agents for efficient targeted drug delivery. Here, we created a Fe₃O₄-based magneto-luminescent Fe₃O₄@SiO₂-CdTe quantum dots nanocomposites and studied PL kinetics and magneto-luminescent properties of nanocomposites in biocompatible solvents. We showed that welding a shell of mesoporous SiO₂ onto spherical Fe₃O₄ nanoparticles prevents oxidation of Fe₃O₄ and saves their magnetic properties.

The research of zinc oxide tetrapods is a promising direction in the nano- and micro-materials field due to their unique properties. Firstly, the shape of tetrapods prevents their aggregation which is shortcomings of spherical and rod nanostructures. Secondly, zinc oxide is a non-toxic and biocompatible material. It makes zinc oxide structures are well suited for environmental, energy, and biomedical applications. Photocatalysis is one of zinc oxide’s key applications because of the high efficiency of reactive oxygen species (ROS) generation, i.e. superoxide radicals and hydroxyl radicals. Surface passivation of zinc oxide tetrapods with magnetic nanoparticles can increase their photoactivity due to effective charge separation which is useful in photocatalysis. Moreover, induced magnetic properties can be used for magnetic separation. In this work, magnetite nanoparticles were chosen as the magnetic component since they have high magnetic susceptibility, demonstrate biocompatibility and low toxicity. Various approaches to a simple formation method of such structures are considered. The composites are obtained by mixing components in water in combination with: (i) ultrasound, (ii) magnetic stirring, (iii) vortex. The samples are studied using scanning electron microscopy, absorption and luminescence spectroscopy. The results confirm that magnetite nanoparticles bind to the zinc oxide tetrapods surface in all three approaches. The photocatalytic activity of the composites is investigated using methylene blue and methyl orange as ROS indicators under light irradiation and is compared with one of the pure zinc oxide tetrapods.

Generally, the spontaneous emission rate of an emitter is computed via classical electromagnetic simulations, modelling the dipolar source as a point. The quantum and classical simulations usually give identical results, since the size of the quantum emitter (QE) is orders of magnitude smaller than the wavelength. However, close to nanophotonic structures sustaining strongly confined fields, such as graphene and other 2D materials, the approximation is not valid anymore: the dipolar transition is no longer dominant and can be surpassed by the rates of higher-order transitions i.e. transitions beyond the dipolar one, such as two-photon processes, electric and magnetic multipolar transitions. . . The determination of these rates requires the spatial variation of the Green’s function along the spatial extent of the QE, which is not easily accessed by conventional numerical solvers. Here, we compute the high-order transition rates of a hydrogen-like atom close to graphene nanoislands (triangle and crescent geometries), by developing a method valid for any material of any shape, and show, as an example, quadrupolar transition rates becoming 100 times larger than dipolar ones. Engineering the high-order transitions through the complex nanophotonic environment promises new infrared sources, entangled two-photon sources and other novel physical effects.

The SERS-based detection of DNA and protein sequences with single nucleotide or amino acid sensitivity still represent a huge challenge. Recently, a new method based on the trapping of a gold nanoparticle in a plasmonic nanohole has been demonstrated. The plasmonic platform obtained by the combination of a nanoparticle trapped inside a nanopore enables to generate a single SERS hot spot for single-molecule detection with a spatial resolution high enough to resolve single element within a biomolecule. The superior spectral and spatial resolution of this approach can be applied to single DNA molecule and single-protein analysis, fingerprinting, and sequencing.

Photonic crystals can serve as the basis for rewritable paper systems due to their structural color and its responsiveness to external stimuli. The present study reports on a hollow sphere colloidal photonic crystal system encapsulated by a poly(ethylene glycol) diacrylate polymer matrix. By exposing this system to an ionic liquid ink, the polymer will locally swell, red shifting its structural color away from its neutral blue state. The size of the shift is dependent on the type of ionic liquid and the exposure time. This system was shown to attain a maximum shift of 133 nm, which covers the entire RGB spectrum. Both the shift of the structural color as well as the rewritability of the system after water rinsing was confirmed through reflectance measurements. The use of a non-volatile ionic liquid ink ensures the stability of the system over time, allowing for its use as a durable written information storage system.

The absorption of electromagnetic energy is one of the most fundamental processes that is used in many different applications, which include photovoltaics, wireless energy transfer, molecular sensing and photodetection. Increasing absorption efficiency is the key to the development of these areas. The phenomenon of total absorption consists of the absorption by the scatterer of all incident energy. Traditional approaches for constructing systems that support total absorption involve the use of extended absorbers or incident fields containing components that rapidly attenuate with distance to the absorber. In this work, we present an approach that allows the coherent total absorption phenomena in individual nanoparticles above the substrate. We demonstrate that it is possible to achieve perfect absorption using a focused beam with some given spatial distribution. This beam corresponds to a set of nanoparticle parameters for which the condition of total absorption is fulfilled. The obtained results are confirmed by full-wave simulations.

Second and third-harmonic generation subjected to an external electric field in a strongly oblate ellipsoidal quantum dot have been studied in the framework of the present work. The adiabatic approximation has been used to divide the system into two subsystems and solve the problem analytically. The calculations have been applied for the strongly oblate ellipsoidal quantum dot made of GaAs. The influence of the external electric field on the matrix element change for the quantum transitions between energy levels of the electron have been discussed. As the obtained results show the increase of the electric field causes the peaks of the second and third-harmonic generation to rise and blueshifts their positions of the spectrum. However, the increase of the semi-minor axis of the strongly oblate ellipsoidal quantum dot leads to a redshift of the resonant peaks and a rise in their magnitudes.

At the present time, hybrid nanostructures attract significant attention among researchers because such materials allow combining advantages of different materials. For instance, the ability of metal nanoparticles to localize electromagnetic energy can be combined with low losses in the visible range of high-index nanoparticles. In this work, we demonstrate the method of creation of hybrid Au/TiO₂ spherical nanoparticles using nanosecond pulsed laser ablation in deionized water. A titanium foil with a sprayed gold film of various thicknesses was used as an initial sample. The effect of the thickness of the gold film on the morphology of the obtained hybrid structures was demonstrated via SEM, and the elemental composition of the created nanoparticles was studied using EDX. The size distribution of the obtained nanoparticles was studied using DLS. We believe the obtained results create the basis for the development of affordable and efficient photocatalysts operating in the visible wavelength range.

The hybrid nanomaterials based on inorganic matrix and organic compound with customizable properties have practical potential in the field of new developments in biological and chemical sensors, photonic and solar cell devices, as well as laser media. The optical properties of molecular clusters so called J-aggregates embedded in nanoporous aluminum oxide in presence of silver plasmonic nanoparticles were studied. The unique technique for obtaining nanoporous aluminum oxide on the island silver film was proposed. The optimal parameters of the impregnation of nanopores in the ethanol solution of pseudoisocyanine dye for the J-aggregate formation have been studied. The resonant transfer of optical energy from the oxygen vacancy in aluminum oxide to organic molecules was observed in the resulting hybrid films.

This work improves period uniformity over larger-area gratings in a two-spherical beam interference lithography (IL) setup. Using a concave vacuum chuck, we have experimentally demonstrated the modified optical setup to reduce period variation (chirp) on a 4-inch silicon substrate. The change in the grating period is significantly reduced compared with the interference exposure on a flat silicon substrate. Wavefront aberration measurement on a curved exposed substrate showed improved grating linearity.

Fabrication of optoelectronic devices relies on the expensive, energy-consuming conventional tools such as chemical vapor deposition, lithography, and metal evaporation. Furthermore, the films used in these devices are usually deposited at elevated temperatures and under vacuum that impose further restrictions to the device fabrication. Developing an alternative technology would contribute to the efforts on achieving a more sustainable optoelectronics technology. Keeping this focus in our focus, here we present a simple technique to fabricate visible photodetectors. These fully solutionprocessed and transparent metal-semiconductor-metal photodetectors employ silver nanowires (Ag NW) as the transparent electrodes replacing the indium-tin oxide (ITO) commonly used in optoelectronic devices. By repeatedly spin coating Ag NWs on a glass substrate followed by the coating of ZnO nanoparticles, we obtained a highly conductive transparent electrode reaching a sheet resistance of 95 Ω/□ as measured by the four-probe method. Optical spectroscopy revealed that the transmittance of the Ag NW-ZnO films was 84% at 450 nm while transmittance of the ITO films was 90% at same wavelength. Following the formation of the conductive film, we scratched it using a heated surgical blade to open a gap. The scanning electron microscope images indicate that a gap of ~30 mm is opened forming an insulating line. As the active layer, we drop-casted red-emitting CdSe/ZnS core-shell quantum dots (QDs) on to this gap to form a metal-semiconductor-metal photodetector. These visible QD-based photodetectors exhibited responsivities and detectivities up to 8.5 mA/W and 0.95x10⁹ Jones, respectively. These proof-of-concept photodetectors show that the environmentally friendly, low-cost, and energy-saving technique presented here can be an alternative to conventional, more expensive, and energy-hungry techniques while fabricating lightharvesting devices.

The luminescence of organic semiconductors can be enhanced by surface plasmon resonance on metal nanoparticles, so it can pave the way for the development of light modulators, laboratory chips or sensors based on organic semiconductors. Silver nanoprisms and nanospheres are two-dimensional plasmonic nanostructures that have attracted massive attention due to their strong shape-dependent related applications and optical properties. When the lateral dimension of silver nanoplates is much larger than the thickness, they possess a very great degree of anisotropy, which favors a high tunability of their localized surface plasmon resonance and maximum electromagnetic-field enhancement therefore is generated. Within this work, silver nanoparticles (nanoprisms and nanospheres) of different sizes were obtained in aqueous solution, which were stabilized with sodium citrate and PVP (Polyvinipyrrolidone). Most luminophores are insoluble in water, so nanoparticles had to be transferred to the organic environment. This was achieved using the ultrasonic method. The obtained nanoparticle solutions were added to organic luminophore DWK-1-TB solution. Before nanoparticles were applied to thin films together with organic luminophore (DWK-1-TB), their properties (absorption, quantum yield, excitation, emission) were studied. Thin films were coated from these solutions. Thin films were applied by spin coating and blade casting method. Different concentrations of silver nanoparticles solutions were coated, as well as films of different thickness. PMMA (polymethyl methacrylate) was added because the nanoparticles efficiently transfer into the PMMA solution and its presence at low concentrations improves the homogeneity of the thin film. Quantum yield, change in luminescence depending on the type of nanoparticles, as well as film thickness were studied in the obtained samples.

Plasmonic nanostructures can efficiently absorb and scatter light, and thus exhibit vibrant colors. Colors originate from the excitation of plasmon resonances – collective oscillations of free electrons in metallic nanoparticles. Semicontinuous metal films (SMF) are a special type of disordered plasmonic structures that can be mass-produced in a rather inexpensive physical vapor deposition process. SMFs are comprised of random in their nature nano-island structures of various sizes and shapes resonating at different wavelengths. When irradiated with high-intensity laser radiation, the nanostructures can be locally modified. Spatially local restructuring originates from highly localized SMF absorption of light in hotspots, regions of a high local electric field. Thus, the optical response of the film can be altered in a spectrally selective manner. Hence, locally different colors are obtained. In this work, we demonstrate the generation of structural plasmonic colors through femtosecond laser-induced modification of thin semicontinuous aluminum films deposited on an aluminum mirror coated with an isolator layer. The structures show vivid colors in reflection. The effects of laser parameters on final color are explored. In addition, we report laser-induced control of diffuse reflectance of aluminum SMF structures. Self-passivation effect of aluminum results in the long-term stability of generated colors.

A carbon nanotube (CNT) can be considered as a plasmonic waveguide enabling propagation of ultraslow (with the effective refractive index >100) surface electromagnetic waves in the THz range. In this work, we theoretically study excitation of SPPs in array of double-walled CNTs by electron beam. The most interesting specific features of the double-walled CNT modes are associated with the presence of interlayer modes enabling a strong confinement of the electromagnetic field between the nanowalls of CNT and thus providing a high deceleration coefficient at a relatively low absorption coefficient at the frequencies up to 40–50 THz. Due to the strong SPP confinement between nanowalls the neighboring CNTs have almost no effect on each other. Array of double-walled CNTs ensuring an effective conversion of the external pump energy into the SPP energy can be employed for design of slow-wave plasmonic nanostructures.

Optical methods have been studied and used extensively for diagnostics and treatment of bio-tissues and cells. Yet, the quality of these methods is still biased by low optical contrast, background noise and heating. Therefore, the ability to track an object's location in cells and tissues is lacking. Here, we report on a method of optically moving gold nanoparticles in a temperature-mediated manner via a structured light - photonic hook. Since continuous wave (CW) generated photonic hooks are extremely weak in low-contrast media, we amplify the optical forces by using pulsed illumination. Our system consists of a micro-cylinder illuminated by an incident Gaussian pulse, and a mask controlling the asymmetry of the incident light. We show that the generated optical forces are around fifteen orders of magnitude larger than by illuminating with a continuous wave of equivalent average power. The photonic hook is applied to a gold nanoparticle embedded in liquid. By investigating the thermo-optical properties of metallic nanoparticles, we present the displacement of the gold nanoparticle, as a result of the momentum exchange. The displacement and changes in polarizability of the gold nanoparticle are examined.

We present the multiple trapping of microspheres using structured diffractive lenses in a setup of optical tweezers. Diffractive lenses are experiencing a wide development due to their successful implementation in areas such as ophthalmology or biophysics. The implementation of multifocal diffractive lenses in an experimental arrangement of optical tweezers affords the generation of multiple traps in a stable and controlled manner. We carried out the multiple trapping of polystyrene microspheres of radius ∼ 2 − 2.4 μm immersed in distilled water. An infrared laser and a multifocal diffractive lens enabled a set of axial foci. The structured lens is generated in a spatial light modulator (SLM) calibrated for a 2π phase shift at λ = 1064 nm and the tailored beam is focused by a high numerical aperture objective. Each focal point generated by the lens acts as a separate optical trap, whereby the confinement of an individual microsphere is possible. The versatility provided by structured diffractive lenses allows increasing the number of optical traps by modifying the lens profile. In addition, such strategy increases the flexibility in the experimental arrangement of optical tweezers.

Quantum dots (QDs) are promising materials for advanced light-emitting diodes (LEDs). Their high thermo- and photostabilities compared to the currently used organic materials allow achieving a greater device brightness due to a higher current density. However, the imbalance of the carrier injection/transport rates is one of the weakest points of QD-based LEDs (QDLEDs), because excess charges accumulated in the emitting layer quench light emission due to various nonradiative processes. The imbalance of charge carrier transport rates in QDLEDs is related to the high potential barrier for hole injection into the QD layer, accompanied by a greater mobility of negative charges in the electron transport layer. To solve this problem, an electron-blocking layer (EBL, made, e.g., of PMMA) can be introduced, which makes it possible to regulate the flow of electrons into the emitting layer. Here, we have theoretically and experimentally investigated the dependence of the luminosity and current efficiency of a multilayer QDLED with the ITO/PEDOT:PSS/poly-TPD/PVK/QDs/PMMA/ZnO/Al structure on the thickness of its EBL. For this purpose, a series of devices was fabricated with the PMMA layer thickness ranging from 0.13 to 3.1 nm. By tuning this thickness, we have fabricated a device with a brightness exceeding that of the control device without EBL by a factor of four, current efficiency increased by almost an order of magnitude, and turn-on voltage lowered by about 1 V. Therefore, it can be concluded that tuning the EBL of a QDLED is a promising strategy to improve charge carrier balance and thereby achieve efficient light emission.

In the last decade, solid-state nanopores have been intensively investigated as label-free detectors of for single biological entities, such as protein chains or DNA molecules. With this approach, single entities are typically driven through a nanopore by applying an external electrical potential. However, this method cannot enable control over the speed of translocation, thus limiting the signal integration time. The most explored approach to introduce control of the translocation speed is based on trapping. In particular, a long acquisition time can be obtained by trapping a nanoparticle tagged with molecules close to a nanopore. The trapping phenomena can be generated by means of external stimuli such as light excitation and magnetic field application, obtaining respectively the so-called optical and magnetic trapping. Magnetic trapping, in particular, has been less explored but can be a useful approach to obtain very large trapping forces without interfering with other optical exitations that can be used for spectroscopic purposes. Here, we will briefly summarize the major examples of magnetic trapping approaches reported so far in solid-state nanopore technology.

Surface-enhanced Raman scattering (SERS), a variant of Raman spectroscopy, is a powerful analytical technique that exploits plasmonics to obtain detailed chemical information of molecules or molecular assemblies adsorbed or attached to nanostructured metallic surfaces. In this work, we have presented a design of easy to fabricate, flexible and cost-effective SERS substrate constituting of chemically synthesized Ag nanoparticles (particle size of 10^-15 nm) embedded superficially on hot-melt adhesive (bio-grade quality) commonly referred as glue stick and used as adhesive. The laser source with λ=785nm is irradiated on the substrate on which the sample to be identified/analyzed is drop-cast, here we have used Rhodamine 6G (R6G) (sigma Aldrich) as probe molecule. The resonant wavelength of Ag NPs was determined using UV-Visible spectroscopy and was found out to be ~ 408 nm. SERS can be used to identify an unknown analyte (provided it should be Raman active) on the basis of its Raman signature. We have demonstrated the detection of R6G (20μL) upto10^-4 M (~4.8 ppm) concentration on our in-house Raman setup using this SERS substrate. This set-up can be easily used to detect/identify different analytes at much lower concentrations. All Raman peaks of R6G were distinctively visible for analysis. We can use this SERS substrate for on-site narcoanalysis, forensic study, explosive detection, bio-diagnostics, detection of adulterants in food/water etc. using portable Raman spectrometer for rapid analysis, with no sample preparation time.

Molecular transfer across cellular membranes into living cells represents a fundamental technical challenge for the biological sciences. Within the biomedical field, a variety of laser-based transfer methods have been explored and successfully applied. In the most abundant approach, a NIR fs laser is tightly focused on the cellular membrane in order to achieve transient permeabilization and a diffusion-driven volume exchange. However, this approach is limited by the single-cell throughput. Plasmonic nanoparticles have proven as viable mediator to dramatically improve the throughput of laser-based molecular delivery within a process termed gold nanoparticle mediated (GNOME) laser transfection: membrane bound nanoparticles are illuminated by 532 nm, 850 ps laser pulses, leading to a confined nanoheater effect. With careful selection of the process parameters, the effect is localized to tens of nanometers around the nanoparticles and can achieve efficient and gentle transient permeabilization of the cellular membrane using a scanning laser setup. This approach has been successfully utilized to deliver a variety of molecules into different mammalian cell types. Herein, we investigate for the first time GNOME laser transfection in the context of plant cells. Plant cells are a promising target for manipulation via genome editing for breeding purposes, but delivery efficiencies for genome editing tools like CRISPR/Cas9 ribonucleotide complexes are still limited. For RNOME laser transfection, as well as for other laser based delivery approaches, the plant cell architecture yields several hurdles. The cells wall represents a quit rigid barrier for molecules above the size exclusion limit of about 40 to 60 kDa. Permeabilization of the cell wall requires high laser energy, which could raise concerns regarding the viability of the cells. In addition, the turgor would induce an outwards driven volume flow upon permeabilization. The presented approach therefore includes the formation of protoplasts from climate chamber cultivated Nicotiana benthamiana plant in isotonic solution before the incubation with the gold nanoparticles. Nanoparticles and protoplasts are brought into close vicinity by a centrifugation approach, before laser illumination of the sample. We investigate the impact of different process parameters (e.g. incubation conditions, laser fluence, scanning speed, …) on the viability and delivery efficiency of marker molecules. The presented approach provides the basis for future vector free genome editing of plant cells.