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The optical properties of gold nanoparticle clusters are presented from the point of view of their applications in biophotonics, where the absorption and scattering spectra are crucial. Generalised multiparticle Mie theory and finite difference time domain (FDTD) technique are used for theoretical description of the far- and nearfield optical properties of two dimensional nanoparticle ensembles. The system under consideration consists of spherical gold nanoparticles from 20 to 200 nm in diameter, forming 2D clusters in water. The properties of the far-field absorption and scattering spectra as a function of the cluster size, particle dimensions, and interparticle distance are investigated for ordered hexagonal structure of the particle arrays. It is found that the absorption efficiency can be shifted to the IR spectral range by increasing array size and decreasing interparticle distance. The increase in the array size also results in enhancement of the scattering efficiency while the absorption is reduced. The near-field intensity distribution is inhomogeneous over the array, as formation of zones with intensity enhancement of about two orders of magnitude is observed in specific areas. The optical properties of an ensemble whose configuration is reproduced from real experiments of gold nanoparticle deposition onto cancer cells are also presented. The results obtained can be used in designing of nanoparticle arrays with applications in biophotonics, bioimaging and photothermal therapy.

We demonstrate the possibility to fabricate wire structures composed by arranged magnetic particles using pulsed laser deposition (PLD) in the presence of a magnetic field. Ablation of Ni and Co targets was performed in air by nanosecond laser pulses delivered by a Nd:YAG laser system oscillating at 355 nm. Due to the high density of the ambient, particles and clusters were formed by condensation in the plasma plume close to the target. The strong deceleration of the ablated material under these conditions further benefited the efficiency of applying a magnetic field to the plume. We also studied the effect of the target-to-substrate distance and the ambient pressure on the morphology of the deposited structures.

The medical-grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial in medicine for preparation of high-tech devices because of its remarkable properties. In this paper, we present experimental results on surface modification of PDMS elastomer by using ultraviolet, visible, and near-infrared ns-laser system and investigation of the chemical composition and the morphological structure inside the treated area in dependence on the processing parameters – wavelength, laser fluence and number of pulses. Remarkable chemical transformations and changes of the morphological structure were observed, resulting in the formation of a highly catalytically active surface, which was successfully functionalized via electroless Ni and Pt deposition by a sensitizing-activation free process. The results obtained are very promising in view of applying the methods of laser-induced micro- and nano-structuring and activation of biopolymers' surface and further electroless metal plating to the preparation of, e.g., multielectrode arrays (MEAs) devices in neural and muscular surface interfacing implantable systems.

This study deals with the development of a novel technique for formation of advanced Ag nanostructures (NSs) to be applied to high-resolution analyses based on surface enhanced Raman scattering (SERS). It has direct bearing on human health and food quality, e.g., monitoring small amount or traces of pollutants or undesirable additives. Three types of nanostructured Ag samples were produced using ion-beam deposition at glancing angle (GLAD) on quartz. All fabricated structures were covered with BI-58 pesticide (dimethoate) or Rhodamine 6G (R6G) for testing their potential for use as substrates for (SERS).

Thin Er3+, Yb3+ co-doped Y2O3 films have been grown on (001) SiO2 substrates by pulsed laser deposition from ceramic targets. The influence of the active ion concentration and processing parameters on the structure, cathodoluminescent (CL) spectra and optical properties of the films have been investigated. The films were prepared in an oxygen atmosphere at pressures of 0.01 and 0.1 mbar and at 500°C substrate temperature. Blue, green and red light emissions centred at 408 nm, 562 nm and 660 nm, respectively, and an infrared (IR) spectrum centred at 1.54 µm were measured. The intensities of the CL peaks strongly depend on the Er and Yb ion concentration in the films and their ratio. An increase in Yb content at a fixed Er concentration leads to a decrease in the CL intensity in the visible range. It is higher for the films deposited at 0.1 mbar, which correlates with the better crystallinity obtained. Despite their better crystallinity, the films prepared at 0.01 mbar have a slightly higher optical transmission in the visible and near-IR range, which corresponds to the smoother surface and lower absorption measured.

Ablation of Fe by ultrashort laser pulses with durations 0.1, 1, and 5 ps were investigated experimentally. The laser fluence varied from the ablation threshold up to 100 J cm−2. Above 1 J cm−2, the ablation rate depended on the laser pulse duration, with the shortest pulse producing the highest value. A change in the ablation rate as the laser fluence increased was also observed. These results were analysed using molecular dynamics simulations. We show that the change in the ablation rate is connected to an overheating of the material above the critical point, which results in a steep rise of the pressure developed. Furthermore, due to the electron heat diffusion, the overheated volume increases and involves material located deeper than the skin depth. An increase in the pulse duration results in a decrease in the degree of overheating.

The medical-grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial in medicine and for preparation of high-tech devices because of its remarkable properties. In this work, we present the experimental results on drilling holes on the PDMS surface by using ultraviolet, visible or near-infrared ns-laser pulses and on studying the changes of the chemical composition and structure inside the processed areas. The material in the zone of the holes is studied by XRD, ?-Raman analyses and 3D laser microscopy in order to obtain information on the influence of different processing laser parameters, as wavelength, fluence and number of consecutive pulses on the material transformation and its modification.

The paper presents a study of a physical method for fabrication of two-dimensional (2D) arrays composed of multi-component nanoparticles on a dielectric substrate. The method consists of two steps. In the first one, thin films composed of different metals are deposited by a classical PLD technique by using targets consisting of sections of different materials. Thin films composed of mixtures of different metals, as gold, silver, nickel, cobalt, iron, platinum, are thus deposited on a quartz substrate. By changing the area of the different sections in the target, thin films with different concentration of the metals are produced. The films fabricated are then annealed by nanosecond laser pulses delivered by a Nd:YAG laser system operating at its third harmonic. The modification of the films is studied as a function of the parameters of the incident radiation, as number of pulses and laser pulse fluence. It is found that the laser annealing can lead to a decomposition of the film into a monolayer of nanoparticles with a narrow size distribution. The optical properties of the structures produced are analyzed on the basis of their transmission spectra. The structures can be used in surface enhanced Raman spectroscopy (SERS) and magneto-optics.

In this work, ZnO nanostructures were fabricated on metal (a metal alloy containing Fe, Cr, Mn and Ni) coated silicon substrates by applying pulsed laser deposition. The samples were prepared at substrate temperatures in the range of 550 – 650 °C, oxygen pressure of 5 Pa, and laser fluence ≤ 1 J cm−2 i.e., process parameters usually used for thin-film deposition. We found that the metal layer's role is substantial in the preparation of nanostructures, the morphology of the catalyst layer determines the growth of the ZnO nanowalls and the increase of the process temperature leads to nanorods formation on the nanowalls.

The study prsented is focused on the optical properties of ZnO/AgNPs/ZnO multilayer nanocomposites. The optical properties of the nanostructures depend on the silver layer thickness. The optical spectral characteristics of Ag nanoparticles (AgNPs) nanostructured by laser irradiation in a ZnO medium were investigated theoretically and experimentally. The extinction spectrum was determined as a function of the nanoparticles size distribution and of the surrounding medium. The extinction efficiency calculated is red-shifted and broadened when the AgNPs are introduced in a ZnO environment. This result is in agreement with the experimental measurements, where the plasmon resonance peak position of the ZnO/AgNPs/ZnO composite is red-shifted, compared to the AgNPs/ZnO sample. Raisng the thickness of the Ag layer increases the resonance extinction. We also propose a method for controlling and tuning the SPR-based sensing of Ag nanoparticles in a ZnO medium.

The subject of the present work is different types of nanostructured ZnO films produced by pulsed laser deposition. The influence was investigated of the surface morphology on the physicochemical and optical properties of the nanostructured films. X-ray photoelectron spectroscopy was used to study the composition and chemical state of the nanostructured ZnO. The changes occurring on the surface of the films after prolonged exposure in air are considered in the light of practical applications of ZnO films. The change in the number of adsorbed species on the surface with the time affects the surface conductivity, the latter in turn modifying the optical properties of the samples.

Highly textured pure and Al doped ZnO thin films have been produced by pulsed laser deposition for optical gas sensor application. The influence of the processing parameters such as substrate temperature and oxygen pressure applied during depositions, and dopant concentration on the structural, morphological, and optical properties of the films were investigated. All deposited films are textured along the (002) direction. The substrate temperature and the oxygen pressure have stronger influence on the film crystallinity compared to the presence of the dopants. The grain size of the films prepared from 2 wt% Al2O3 doped ZnO target is approximately the same as the one produced from pure ZnO tagret. The increase in the dopant concentration into the ZnO target (to 5 wt% Al2O3) leads to an increase of the in-plane grain size of the as-deposited films which is well known to increase the gas sensitivity. At the same time, the use of doped targets increase the droplets on the film surface which deteriorates the optical detection of the gas sensing effect. The increase of the dopant concentration reduces the film transmission in the visible range and the transmission cut-off edge is shifted to the shorter wavelengths. The films deposited from 2 wt% Al2O3 doped ZnO target at oxygen pressure of 0.05 mbar and 300°C substrate temperature have good mode properties which makes them good candidates for optical sensors.

Refractometric sensor elements were studied consisting of a side-polished single-mode optical fibre covered by a pulsed laser deposited ZnO thin film. A measurement scheme was used for in situ control of the film thickness during the deposition process. Highly sensitive sensors were produced based on the interaction with the zero- and first-order modes of the ZnO planar waveguide. The sensors' applicability to the two spectral regions for communications, namely 800–1000 nm and 1300–1600 nm, was demonstrated. A high sensitivity of the order of 3000–6700 nm per refractive index unit change was obtained for sensor elements utilizing the interaction of the fibre mode with the TE0 or TM0 mode of the ZnO thin-film waveguide.

The dependence on laser wavelength of the process of nanoparticle generation by ultrashort laser ablation of solid matter in a vacuum has been investigated both experimentally and theoretically. The study has been carried out for a Ni target by using laser pulses of approximate to 300 fs duration at two different laser wavelengths: in the visible (lambda = 527 nm) and ultraviolet (lambda = 263 nm), respectively. The size distribution of the nanoparticles, which is quite broad in the case of visible light, becomes significantly narrower and slightly shifts towards smaller sizes for ultraviolet light. Molecular dynamics simulations confirm the dependence of the process on the laser wavelength by showing that the laser photon energy affects the material relaxation and, thus, the nanoparticle generation process. This, in turn, indicates that the photon energy can be used as an effective parameter to control the nanoparticle size distribution in femtosecond laser ablation of solid matter.