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Medical grade polydimethylsiloxane (PDMS) elastomer is a biomaterial widely used in medicine and high-tech devices, e.g. MEMS and NEMS. In this work, we report an experimental investigation on femtosecond laser processing of PDMS-elastomer with near infrared (NIR), visible (VIS) and ultraviolet (UV) pulses. High definition trenches are produced by varying processing parameters as laser wavelength, pulse duration, fluence, scanning speed and overlap of the subsequent pulses. The sample surface morphology and chemical composition are investigated by Laser Microscopy, SEM and Raman spectroscopy, addressing the effects of the various processing parameters through comparison with the native materials characteristics. For all the laser pulse wavelengths used, the produced tracks are successfully metalized with Ni via electro-less plating method. We observe a negligible influence of the time interval elapsed between laser treatment and metallization process. Our experimental findings suggest promising perspectives of femtosecond laser pulses in micro- and nano-fabrication of hi-tech PDMS devices.

This article presents experimental investigations of effects of the process parameters on the medical grade polydimethylsiloxane (PDMS) elastomer processed by laser source with irradiation at UV (266 and 355 nm), VIS (532 nm) and NIR (1064 nm). Systematic experiments are done to characterize how the laser beam parameters (wavelength, fluence, and number of pulses) affect the optical properties and the chemical composition in the laser treated areas. Remarkable changes of the optical properties and the chemical composition are observed. Despite the low optical absorption of the native PDMS for UV, VIS and NIR wavelengths, successful laser treatment is accomplished due to the incubation process occurring below the polymer surface. With increasing of the fluence and the number of the pulses chemical transformations are revealed in the entire laser treated area and hence decreasing of the optical transmittance is observed. The incubation gets saturation after a certain number of pulses and the laser ablation of the material begins efficiently. At the UV and VIS wavelengths the number of the initial pulses, at which the optical transmittance begins to reduce, decreases from 16 up to 8 with increasing of the laser fluence up to 1.0, 2.5 and 10 J cm −2 for 266, 355 and 532 nm, respectively. In the case of 1064 nm the optical transmittance begins to reduce at 11th pulse incident at a fluence of 13 J cm −2 and the number of the pulses decreases to 8 when the fluence reaches value of 16 J cm −2 . The threshold laser fluence needed to induce incubation process after certain number of pulses of 8 is different for every wavelength irradiation as the values increase from 1.0 for 266 nm up to 16 J cm −2 for 1064 nm. The incubation and the ablation processes occur in the PDMS elastomer material during its pulsed laser treatment are a complex function of the wavelength, fluence, number of pulses and the material properties as well.

The paper presents results on laser nanostructuring of Ag thin films. The thin films are deposited on glass substrates by pulsed laser deposition technology. The as fabricated films are then annealed by nanosecond laser pulses delivered by Nd:YAG laser system operated at λ = 355 nm. The film modification is studied as a function of the film thickness and the parameters of the laser irradiation as pulse number and laser fluence. In order to estimate the influence of the environment on the characteristics of the fabricated structures the Ag films are annealed in different surrounding media: water, air and vacuum. It is found that at certain conditions the laser treatment may lead to decomposition of the films into a monolayer of nanoparticles with narrow size distribution. The optical properties of the fabricated nanostructures are investigated on the basis of transmission spectra taken by optical spectrometer. In the measured spectra plasmon resonance band is observed as its shape and position vary depending on the processing conditions. The fabricated structures are covered with Rhodamine 6G and tested as active substrates for Surface Enhanced Raman Spectroscopy (SERS).

Laser ablation of a gold thin film irradiated by ultrashort pulses is studied using molecular-dynamics simulations, and compared with that of a bulk target. A film thickness comparable to the ballistic electron depth in gold (≈ 100 nm) is considered, evidencing a significant change of the temperature spatial profile inside the target material, which eventually influences the material decomposition. Particular emphasis is given to the process of nanoparticle generation. The simulations indicate a more uniform heating of the sample in the case of the thin film, which is accompanied by a more homogeneous size distribution of the nanoparticles produced in the ablation process. An experimental characterization of the ultrashort-pulse ablation process is also carried out. The produced nanoparticles are collected on suitable substrates, and atomic force microscopy analysis of less than one layer deposits is performed. An ≈ 2 × narrowing of the nanoparticles equivalent to spherical diameter size distribution is observed in the case of ablation of the gold thin film, in fairly good agreement with the theoretical predictions. Moreover, interesting changes of the nanoparticle shape are evidenced, which are correlated to the changes in the nanoparticle ablation plume dynamics, as studied by time-gated imaging of its self-emission. Our findings suggest ultrashort-pulse laser ablation of thin films as a viable route to achieve a more uniform nanoparticle size distribution.

Contamination-free Ag nanoparticles were produced by nanosecond pulsed laser ablation (10 Hz repetition rate, 15 ns pulse duration) of a solid target immersed in double distilled water. The size distribution observed of the NPs is wider compared to those obtained by other preparation methods, mainly chemical. To modify it and make the NPs more appropriate for biological application, the fabricated suspensions were irradiated by an unfocused laser beam. The fundamental wavelength (λ = 1064 nm) of a Nd:YAG laser system was used for Ag NPs preparation. It lies outside their surface plasmon absorption band and was chosen to avoid self-absorption during ablation by already formed NPs. Excluding a possible absorption in the preparation stage provides a better control of the irradiation influence. The following irradiation of the suspension obtained was performed by the third (λTHG = 355 nm) harmonic of the laser system, which was chosen due to its positioning within the corresponding surface plasmon absorption band. The changes of the NPs characteristics caused by different laser fluence and duration of irradiation were traced by transmission electron microscopy (TEM) and confirmed by optical transmission measurements in the near UV and the visible region. A considerable narrowing (by about of a factor of three) of the surface plasmon extinction band was achieved, which is evidence of narrowing of the particles size distribution and approach of their shape to the ideal spherical.

A study is presented of Au nanoparticles (NPs) created by nanosecond pulsed laser ablation of a solid target in double distilled water. The influence was examined of the laser wavelength on the size, shape and optical properties of the resulting NPs. Three different wavelengths: the fundamental (λ = 1064 nm), second (λSHG = 532) and third (λTHG = 355) harmonic of a Nd:YAG laser at the same fluence were utilized to produce various colloids. Ablation at the wavelength of 532 nm was investigated in more detail to reveal the influence of self-absorption by the already created NPs on their characteristics. The colloid produced was irradiated by λirrad = 532 nm (laser energy 40 mJ) at different times up to 25 min after the end of ablation. The initial structure of welded NPs forming wires was modified. Transmission electron microscopy and optical transmission measurements were used to evaluate the shape and size distribution of the NPs.

In this paper we present a laser-based method for metal nanostructures formation on flexible substrates. The analysis of the obtained structures is focused on their optical properties. The nanostructures are fabricated by laser processing of gold thin films. The films are deposited on PMMA and PVC substrates by classical PLD technology. The produced films are then annealed by nanosecond pulses delivered by Nd:YAG laser system operated at λ = 355 nm. At certain conditions the laser treatment leads to formation of discrete nanostructure on the substrate surface. The optical properties of samples fabricated at different conditions are examined by optical spectroscopy. Bending of the substrates at different angles is used to modify the characteristics of the produced structure which leads to change of its optical properties. In this way the plasmon band of the obtained nanostructures can be efficiently tuned in a range of about 30 nm. The experiments of using produced structures in Surface Enhanced Raman Spectroscopy show that they can be an efficient alternative of the already developed.

Results are presented on the synthesis and characterization of nanocomposite Ag/ZnO heterostructures on fused quartz substrates. The experiments were performed by pulsed laser deposition (PLD) using a third harmonic Nd:YAG laser in a vacuum chamber. The ablation of a rotated Ag target was followed by laser modification of the deposited layer and subsequent deposition of ZnO. The process factors, such as the silver film thickness and the post-deposition annealing procedures, were varied in view of controlling the diameter and size distribution of the Ag nanoparticles. The annealing regimes were modified by varying the laser irradiation energy on the Ag layers. The effect on the Ag/ZnO properties is discussed. It is demonstrated that the photoluminescence intensity of ZnO nanolayers is significantly enhanced by plasmon absorption in the Ag nanoparticles and a shift to the lower wavelengths.

Preparation of noble metal nanoparticle (NPs) colloids using pulsed laser ablation in water has an inherent advantage compared to the different chemical methods used, especially when biological applications of the colloids are considered. The fabrication method is simple and the NPs prepared in this way are contamination free. The method of laser ablation of a solid target in water is applied in the present work in order to obtain gold and silver NP colloids. The experiment was preformed by using the fundamental wavelength (1064 nm) of a Nd:YAG laser system. The target immersed in double distilled water was irradiated for 20 min by laser pulses with duration of 15 ns and repetition rate of 10 Hz. The sedimentation and aggregation of NPs in the colloids, stored at constant temperature, as a function of the time after preparation were investigated. The analyses are based on optical transmission spectroscopy in UV and vis regions. The change of the plasmon resonance wavelength as a function of time was studied. Zeta potential measurement was also utilized to measure the charge of the NPs in the colloids. The size distribution of the NPs and its change in time was determined by transmission electron microscopy (TEM). On the basis of the results obtained, the optimal conditions of post fabrication manipulation with gold and silver colloids are defined in view of producing stable NPs with a narrow size distribution.

The paper presents results on laser nanostructuring of bimetallic thin films. The thin films are deposited by classical on-axis pulsed laser deposition technology by using targets consisted of two sections composed of different metals. Using this technique gold/nickel or gold/silver thin films are deposited on quartz substrate. By changing the area of the different sections of the target, thin films with different concentrations of the two metals are obtained. The as fabricated films are then annealed by nanosecond laser pulses delivered by Nd:YAG laser system operated at λ = 355 nm. The modification of the produced films is studied as a function of the parameters of the incident irradiation as pulse number and laser fluence, the composition of the thin films, and characteristics of the environment. It is found that the laser annealing may lead to nanostructuring of the films as at certain conditions the thin films are decomposed into a monolayer of nanoparticles with narrow size distribution. The performed EDX analyses indicated that the fabricated particles are composed by a bimetallic system of the basic metals used. The extinction spectra of the obtained structures show plasmon excitations as the resonance wavelength can be efficiently tuned in a wide range by changing the ratio of the basic metals in the films. The obtained structures can be used in SERS and magneto-optics.

Pulsed laser ablation of Ag and Au targets, immersed in double-distilled water is used to synthesize metallic nanoparticles (NPs). The targets are irradiated for 20 min by laser pulses at different wavelengths—the fundamental and the second harmonic (SHG) ( λ = 1064 and 532 nm, respectively) of a Nd:YAG laser system. The ablation process is performed at a repetition rate of 10 Hz and with pulse duration of 15 ns. Two boundary values of the laser fluence for each wavelength under the experimental conditions chosen were used—it varied from several J/cm 2 to tens of J/cm 2 . Only as-prepared samples were measured not later than two hours after fabrication. The NPs shape and size distribution were evaluated from transmission electron microscopy (TEM) images. The suspensions obtained were investigated by optical transmission spectroscopy in the near UV and in the visible region in order to get information about these parameters. Spherical shape of the NPs at the low laser fluence and appearance of aggregation and building of nanowires at the SHG and high laser fluence was seen. Dependence of the mean particle size at the SHG on the laser fluence was established. Comments on the results obtained have been also presented.

Theoretical and experimental results on the heating process of gold nanoparticles irradiated by nanosecond laser pulses are presented. The efficiency of particle heating is demonstrated by in-vitro photothermal therapy of human tumor cells. Gold nanoparticles with diameters of 40 and 100 nm are added as colloid in the cell culture and the samples are irradiated by nanosecond pulses at wavelength of 532 nm delivered by Nd:YAG laser system. The results indicate clear cytotoxic effect of application of nanoparticle as more efficient is the case of using particles with diameter of 100 nm. The theoretical analysis of the heating process of nanoparticle interacting with laser radiation is based on the Mie scattering theory, which is used for calculation of the particle absorption coefficient, and two-dimensional heat diffusion model, which describes the particle and the surrounding medium temperature evolution. Using this model the dependence of the achieved maximal temperature in the particles on the applied laser fluence and time evolution of the particle temperature is obtained.

In this work we show the properties of the electromagnetic field in the vicinity of a monolayer nanoparticle array on SiO2 substrate. The nanoparticle array is produced by a simple experimental procedure, where thin gold and silver films are deposited on a substrate by pulsed laser deposition technique and they are annealed by nanosecond laser pulses. At certain conditions the laser annealing leads to a homogeneous decomposition of the film into nanoparticles with diameters in the range of few tens of nanometers. Using FDTD simulations the near field distribution in array structures taken from SEM images are obtained. The distribution shows presence on “hot spots” where the near field intensity is enhanced more than two orders of magnitude compared to the incident one. The existence of enhanced field intensity is assumed to be the main reason on enhancement of the Raman scattering signal obtained experimentally using the produced structures as active substrates.

In this work, erbium, and erbium and ytterbium co-doped YVO 4 waveguiding thin films were deposited on amorphous SiO 2 substrates by pulsed laser deposition (PLD) and ultraviolet-assisted pulsed laser deposition (UVPLD). The influence of the deposition technique on the structure, morphology, and optical properties of the films was investigated. At lower dopant concentrations the films prepared by UVPLD show better crystallinity and optical properties. All the samples show preferred orientation of the (001) zone axes parallel to the substrate surface. The polycrystalline samples show difference in the refractive indexes ∆ n (∆ n = n TE − n TM ) for the TE and TM polarizations.

Pulsed laser deposition technique was used to fabricate successfully nanostructured optical waveguide films of TiO2 and WO3 − x for gas-sensing applications. High-quality mode spectra, consisting of well-defined bright mode lines were observed in the samples with smooth surface. Films' structural, morphological and optical properties as well as the chemical composition were investigated by using x-ray diffraction, scanning electron and atomic force microscopy, UV–VIS–NIR, m-line and x-ray photoelectron spectroscopy, respectively. Gas sensitivity was investigated at room temperature using m-line spectroscopy technique on basis of reversible variations of the refractive index of the samples under gas exposure. Testing scheme recording the bright m-line shift as optical response was proposed.

In this work the near field properties of a single gold nanoparticle embedded in transparent host medium are investigated theoretically. The analysis of the electromagnetic field in the near field zone is obtained by finite difference time domain (FDTD) simulation technique. The nanoscale system consists of a transparent layer in which a gold particle with diameters of D = 200 or 80 nm is embedded, is situated on a substrate surface. Laser pulse at wavelength of 800 nm irradiates normally this system. It is found that the field in the vicinity of the particle is enhanced, and at a certain condition the zone with the highest enhancement is localized on the substrate surface. Furthermore, the near field characteristics are found to be controllable by the dielectric properties of the host material, substrate, parameters of the incident irradiation and particle size. With the increase of the refractive index of the host medium, both the magnitude of the near field on the substrate and the characteristic size of the field enhanced zone decrease. The influence of the particle size and polarization of the incident laser irradiation on the near filed properties of the system are also presented. The proposed configuration can be applied for a multiple nanoprocessing and an integrated near field source with a spatial resolution of D/3.

Erbium, and erbium and ytterbium co-doped YVO4 waveguiding films were deposited on MgO/Si substrates by PLD. The samples were post-annealed at two different temperatures in air atmosphere. The influence on the crystalline structure and waveguiding properties of the films at these annealing temperatures for two dopant concentrations was investigated. Layers annealed up to 900 °C are polycrystalline. The dominant fraction of YVO4 crystallites exhibited preferred orientation of the (0 0 1) zone axes parallel to the substrate surface. The polycrystalline samples show difference in the refractive indexes Δn (Δn = nTE − nTM) for TE and TM polarizations.

Nanoparticles (NPs) creation by pulsed-laser ablation of targets in a liquid environment has recently become a promising technique, which has several relative advantages, such as simplicity and low cost. This technique was employed in the present work for preparation of TiO x NPs suspension by ablation of metal Ti targets into twice-distilled water. A second harmonic generation (SHG) pulsed Nd:YAG laser was used in the experiments. Preferential formation of spherical NPs and their TiO x nature was established. Aggregation of the created particles during aging was found. Transition of the NPs’ structure from amorphous to crystalline with increasing the laser energy was revealed. A difference was observed in the transmittance of the suspensions obtained depending on the laser intensity.

Vanadium-doped ZnO films (Zn1−xVxO, where x = 0.02, 0.03, 0.05 and 0.07), were formed from ceramic targets on c-cut sapphire substrates using pulsed laser deposition at substrate temperature of 600 °C and oxygen pressure of 10 Pa. In order to clarify how the vanadium concentration influences the films’ properties, structural and magnetic investigations were performed. All films crystallised in wurtzite phase and presented a c-axis preferred orientation at low concentrations of vanadium. The results implied that the doping concentration and crystalline microstructure influence strongly the system's magnetic characteristics. Weak ferromagnetism was registered for the film with the lowest doping concentration (2 at.%), which exhibited a ferromagnetic behavior at Curie temperature higher than 300 K. Increasing the vanadium content in the film caused degradation of the magnetic ordering.

In this work the optical and the gas sensing properties of thick TiO 2 waveguide films, produced by pulsed laser deposition, were investigated by m -line spectroscopy. The films were deposited on (0 0 1) SiO 2 substrates at temperature of 100 °C. The thickness of the films was measured to be in the range from 650 to 1900 nm and the roughness increases from 5 to 14.6 nm. High quality mode spectra, consisted of thin and bright TE and TM modes, were observed in the films with thickness up to 1200 nm. All the films revealed anisotropic optical properties. Gas sensitivity of the films to CO 2 was examined at room temperature on the basis of the variations of the refractive index. CO 2 concentration of 3 × 10 4 ppm was detected, which corresponds to a refractive index variation of about 1 × 10 −4 . The crystal structure and the optical transmittance of the films were also presented and discussed.

In this work, thin ZnO films have been produced by pulsed laser deposition on side-polished fiber for optical gas sensor applications. The influence was investigated of the processing parameters, such as substrate temperature and oxygen pressure applied during deposition, on the sensitivity to ammonia of the sensing element. A shift of the spectral position of the resonance minimum to the longer wavelengths was observed at room temperature for the sample prepared at 150 °C substrate temperature and 20 Pa oxygen pressure. Spectral changes in the range 0.16–1.13 nm for NH 3 concentrations between 500 and 5000 ppm were also observed.

The purpose of the present investigation is the fabrication of undoped and palladium doped indium tin oxide films by pulsed laser deposition and the analyses of their optical, waveguide and structural properties in view of optical sensor applications. The films are deposited at oxygen pressure from 5 to 20 Pa and substrate temperature between 200 and 450 °C. Palladium is used as a dopant since it is critical in improving the sensor's properties. The X-ray diffraction spectra show that all films are polycrystalline with preferential [1 1 1] orientation. The optical transmittance measured in the visible region has maximum values of 85–90% for films grown at oxygen pressure 15 Pa independently of the substrate temperature used. SEM, AFM and optical and investigations revealed that indium tin oxide films with 1 wt.% Pd have higher transmittance and better surface morphology than those with 3 wt.% Pd concentration. ITO films with minimum propagation losses of 2 dB cm −1 were deposited at substrate temperature 200 °C and oxygen pressure 5 Pa, but doped ITO films with minimum propagation losses were obtained at 400 °C and 15 Pa.

In this work, thin YVO 4 films were deposited on amorphous SiO 2 substrates by pulsed laser deposition (PLD). Ceramic targets of pure and doped (Er and Er, Yb) YVO 4 were prepared and used for ablation. The influence of the substrate temperature and oxygen pressure applied during the depositions was investigated. Crystalline films were obtained at temperatures higher than 500 °C. The films with the best crystallinity were obtained at 5 Pa oxygen pressure and 700 °C substrate temperature. All the films are transparent in the visible and near infrared region of spectra. The crystalline samples show difference in the refractive indexes Δ n (Δ n = n TE − n TM ) for the TE and TM polarizations. It was evaluated to be about 0.08.

Symposium on Laser Interaction with Advaned Materials: Fundamentals and Applications, Lille, FRANCE, 2014; International audience; Laser-assisted method for fabrication of nanoparticles on the surface of ceramic substrate is presented. The method is based on laser dewetting of thin metal film deposited on the substrate. Using this technique, gold nanoparticles on alumina ceramic surface are fabricated. It is shown that the processing parameters can influence the properties of the fabricated structure, as at certain conditions a homogeneous cover of nanoparticles with narrow size distribution can be achieved. The processed surfaces are tested as substrates in surface enhanced Raman spectroscopy of a standard dye. The efficiency of the substratesis estimated by the ability of detection of the dye at nM concentration and it is compared to that of thin gold film on ceramic substrate. The strongest enhancement is observed for the sample where Au film is not completely decomposed and the structure consists of thin film and nanoparticles aggregates. The proposed method has potential application in fabrication of cheap and reliable substrates for Raman spectroscopy analysis with high sensitivity and also in catalysis. (C) 2014 Elsevier B.V. All rights reserved.

Medical grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial as encapsulation and/or as substrate insulator carrier for long term neural implants because of its remarkable properties. Femtosecond (λ = 263 and 527 nm) and nanosecond (266 and 532 nm) laser processing of PDMS-elastomer surface, in air, is investigated. The influence of different processing parameters, including laser wavelength, pulse duration, fluence, scanning speed and overlapping of the subsequent pulses, on the surface activation and the surface morphology are studied. High definition tracks and electrodes are produced. Remarkable alterations of the chemical composition and structural morphology of the ablated traces are observed in comparison with the native material. Raman spectra illustrate well-defined dependence of the chemical composition on the laser fluence, pulse duration, number of pulses and wavelength. An extra peak about ∼512–518 cm−1, assigned to crystalline silicon, is observed after ns- or visible fs-laser processing of the surface. In all cases, the intensities of Sisingle bondOsingle bondSi symmetric stretching at 488 cm−1, Sisingle bondCH3 symmetric rocking at 685 cm−1, Sisingle bondC symmetric stretching at 709 cm−1, CH3 asymmetric rocking + Sisingle bondC asymmetric stretching at 787 cm−1, and CH3 symmetric rocking at 859 cm−1, modes strongly decrease. The laser processed areas are also analyzed by SEM and optical microscopy. Selective Pt or Ni metallization of the laser processed traces is produced successfully via electroless plating. The metallization process is not sensitive with respect to the time interval after the laser treatment. DC resistance is measured to be as low as 0.5 Ω mm−1. Our results show promising prospects with respect to use such a laser-based method for micro- or nano-fabrication of PDMS devices for MEMS and NEMS.

Classical molecular dynamics simulation technique is applied for investigation of the iron ablation by ultrashort laser pulses at conditions of deep hole for the first time. Laser pulse duration of 0.1 ps at wavelength of 800 nm is considered. The evolution of the ablated material in deep hole geometry differs completely from the free expansion regime as two major mechanisms are important for the final hole shape. The first one is the deposition of the ablated material on the walls, which narrows the hole at a certain height above its bottom. The second mechanism is related to ablation of the material from the walls (secondary ablation) caused by its interaction with the primary ablated particles. Properties of the secondary ablated particles in terms of the velocity and the angular distribution are obtained. The material removal efficiency is estimated for vacuum or in Ar environment conditions. In the latter case, the existence of well-defined vapor cloud having low center of the mass velocity is found. The processes observed affect significantly the material expulsion and can explain the decrease of the drilling rate with the hole depth increase, an effect observed experimentally.

A theoretical model is developed and a molecular dynamics simulation technique is applied for the description of ultrashort laser ablation of metals. The ablation of Al, Ni, and Fe using 0.1, 0.5 and 5 ps laser pulses at wavelengths of 248 and 800 nm is studied. The process is investigated at fluences up to 0.5 J/cm2. The analysis based on the temporal evolution of the ablation, the temperature, and the pressure distributions into the material reveals that a thermo-mechanical mechanism (spallation) takes place near the threshold. However, phase explosion is found to be the dominant mechanism of material removal at fluences higher than several hundreds of mJ/cm2. The influence of the laser parameters (wavelength and pulse duration) is obtained and discussed. The ablation depth as a function of the laser fluence and the ablation threshold value are evaluated and compared with the experimental data available. Good agreement between the theory and experiments is observed.

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.

Textured (1 1 0)Nd:KGW optical waveguides are grown on CeO 2 /Si substrates by pulsed laser deposition. Ceria buffer layer is prepared on (1 0 0)Si substrates by KrF excimer laser ablation of Ce 0.9 Gd 0.1 O 2 ceramic target. The (1 0 0) or (1 1 1) orientation of CeO 2 depends on the deposition conditions. The Nd:KGW films are prepared by ablation of K-rich ceramic targets in O 2 or Ar. The influence of the synthesis conditions (O 2 or Ar pressure and substrate temperature) and the orientation of the CeO 2 buffer layer on the crystallinity of the Nd:KGW films are studied. Better results are obtained when deposited on (1 0 0)CeO 2 /(1 0 0)Si. The as-grown films are optically active. The crystallinity improves and the intensity of the emission spectra increases upon annealing at 700 °C in air. The emission spectra of Nd:KGW films are demonstrated for the main Nd transitions in 0.85–1.45 μm spectral range. Waveguide loss as low as 3.3 dB cm −1 is 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.

Deposition of thin films by pulsed laser ablation from an Er2O3:Y2O3 ceramic target for waveguide laser application is reported. Erbium-doped yttrium oxide (Er:Y2O3) thin films are grown on c-cut sapphire under optimized deposition parameters. The effects of ultraviolet (UV)-assisted annealing of thin Er:Y2O3 films on the structural properties and the morphology are investigated. The films exhibit better crystalline structure and smoother surface after post-deposition treatment. The optical transmission spectra and the waveguiding properties of the thin films are reported. The films exhibit lower absorption and scattering losses after UV-assisted annealing. The light is guided to the end of the treated films with propagation losses ≈2 dB/cm.

5th European-Materials-Research-Society Symposium on Laser Material Interactions for Micro- and Nano- Applications, Strasbourg, FRANCE, MAY 27-31, 2013; International audience; The experimental conditions were investigated enabling one to fabricate Au nanowire networks by pulsed laser ablation in water. The study revealed that it is possible to produce alternatively nanoparticles (or aggregates) or nanowire networks at certain wavelengths depending on the laser fluence. An Au disc immersed in double-distilled water was used as a target. The second (lambda(SHG) = 532 nm) and the third lambda(THG) = 355 nm) harmonics of a Nd:YAG laser system were utilized to produce different Au colloids. The values of the laser fluence for both wavelengths under the experimental conditions chosen were varied from several J/cm(2) to tens of J/cm(2). The optical extinction spectra of the colloids in the UV/vis region were obtained to evaluate the structure of the dispersed Au phase. Transmission electron microscopy (TEM) was applied to visualize the size and morphology of the colloidal particles. Their structure and phase composition were studied by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) and used to make an assumption on how they had been formed. (C) 2014 Elsevier B.V. All rights reserved.

High-quality epitaxial strontium-hexaferrite (SrFe12O19) thin films were grown by pulsed laser deposition (PLD) on c-cut sapphire using KrF∗ excimer laser at a fluency of 2 J/cm2 and substrate temperature of 800°C in 100 mTorr oxygen environment. The X-ray diffraction (XRD) and morphology analyzes showed films with excellent crystalline structure and flat surface. The thickness was found to influence considerably the surface morphology and magnetic properties of the as-deposited films. The highest orientation and the best morphology with smooth surface and fine grain structure was obtained for the film having a thickness of 750 nm. The highest coercive force of 1453 Oe was measured for this film in perpendicular to the plane direction.

Vanadium doped ZnO thin films (Zn 1 − x V x O, where x = 0.05 or x = 0.13) were grown on c -cut sapphire substrates using pulsed laser deposition technique. Their structure and magnetic properties were examined in relation to the doping concentration. All deposited films were highly oriented along the c -axis and exhibited ferromagnetic behavior with a Curie temperature up to 300 K. The crystal structure was found to be better for layers with lower vanadium concentration. The films had a porous fine-grained microstructure and a column-like character as the V concentration was reduced. A weak dependence of magnetization on temperature was observed. The saturation magnetization was found to be strongly dependent on the crystal structure, grain size and V-ion concentration.

We have investigated ultrashort laser micromachining of metals, both from the point of view of the basic physical processes, and the technological implications. The process of hole drilling of Ni with approximate to 300 fs SHG (X = 527 nm) Nd-glass and Al samples with 100 fs Ti:sapphire (), = 800 nm) laser pulses, respectively, has been experimentally addressed by using time-gated optical emission spectroscopy of the ablated material and SEM analysis of the targets. The ablation process has also been analyzed by classical, molecular dynamics (MD) simulations, by using a Morse potential to describe the interaction between the atoms, and taking into account the electron heat diffusion contribution. The dependence of the ablation depth on laser fluence, as measured by SEM analysis, is in good agreement with the numerical simulations and is also well correlated with the optical emission yield of the expanding plume. (c) 2007 Elsevier B.V. All rights reserved.

International audience; Thin films were grown on (001) SiO2, SiO2/(100) Si or (100) MgO substrates by laser ablation of neodymium-doped potassium gadolinium tungstate (Nd:KGW) single crystal target. The films were deposited at temperatures between room temperature and 750 degrees C and pressures between 1 X 10(-4) Pa and 50 Pa of oxygen ambient. The influence of the deposition conditions on the composition, structure, morphology and electrical properties of the films was investigated. Special attention was paid to the films deposited in vacuum (I X 10(-4) Pa) or at very low oxygen pressures. Under such conditions, the potassium (K), gadolinium (Gd) and oxygen (0) content decreased strongly as the temperature was increased. At room temperature, the films were K and 0 stoichiometric, in contrast with Gd, which showed a concentration twice higher. The films were polycrystalline, with the exception of those deposited at temperatures below 500 degrees C, which were amorphous. However, all were smooth and dense. The films grown in vacuum and at temperatures between 500 and 700 degrees C consist mainly of ``a-tungsten'' - tungsten oxide (W3O) phase. The films grown on SiO2/Si possessed the best surface quality with nano-size relief The resistivity measurements as a function of the temperature showed that the films produced in vacuum and at temperatures below 500 degrees C were highly insulating, whereas at 600 degrees C they exhibited semiconducting behavior or a metallic one at 700 degrees C. This behavior can be attributed to the existence of various valence states for tungsten below W6+ in the films and to their crystal structure. (c) 2006 Elsevier B.V. All rights reserved.

For the laser drilling of aluminum nitride ceramic the processing results and the effects related to pulsed irradiation were investigated. Images of the drilled surface revealed regular, cylindrically shaped holes of about 100 μm in diameter independently of the laser wavelength (1064/532/355 or 266 nm). The holes were surrounded by circular heat-affected zones of larger diameter. A comparison of the elemental compositions of the original material and the processed one indicated a decrease of the nitrogen concentration in the affected area. The spectral analysis of the ablated material composition revealed the presence of ions and neutrals in dependence on the laser intensity applied. It was found that at intensity values close to the ablation threshold the ejected material consisted mainly of neutrals, while doubling of the intensity resulted in appearance of single-ionized Al species, which were also observed together with Al clusters in the mass spectra of the UV-excited plasma. Their prevailing content was revealed for drilling at higher intensities around 15 GW/cm2 at 532 nm. Results of model calculations indicated, in agreement with the experiment, that at the threshold the ceramic decomposes into gaseous nitrogen and solid Al particulates, while at a higher fluence the material particles vaporize and influence the quality of drilling. © 2007 Elsevier B.V. All rights reserved.

We present an experimental characterization and a theoretical analysis of ultrashort laser ablation of a nickel target, which highlights the more general and peculiar features of femtosecond (fs) laser ablation of metals. The study has been carried out by using visible (527 nm) laser pulses of approximate to 300 fs duration. The vacuum expansion dynamics of the ablated species has been investigated by using fast photography and optical emission spectroscopy, while the fs laser pulse-metal interaction has been studied theoretically by means of molecular dynamics simulations. Special attention has been given to the study of the dependence of ablation depth on laser fluence, which has been carried out by comparing the SEM analysis of micro-holes drilled into the nickel samples with the predictions of the theoretical model. The main outcomes of our investigation, which are very satisfactorily reproduced and accounted for by the theoretical model, are (i) the nonlinear dependence of the ablation yield on the laser fluence, and its reliance to the electron heat diffusion, in the process of redistribution of the absorbed energy, (ii) the splitting of the material blow-off into two main classes of species, atoms and nanoparticles, characterized by different expansion dynamics, and (iii) the different degrees of heating induced by the laser pulse at different depths into the material, which causes the simultaneous occurrence of various ablation mechanisms, eventually leading to atoms and nanoparticles ejection.

Thin Er, Yb co-doped Y2O3 films were grown by pulsed laser deposition from ceramic target. Subsequent ion implantation with 1.1 MeV Er+ ions to a fluence of 6 × 1014 at/cm2 at room temperature was performed in order to modify the structure of the as-deposited films. The as-deposited films have a polycrystalline column-like structure. Ion implantation induces defects into the as-deposited films. After annealing at 900 °C for 1 h in oxygen atmosphere, the films recrystallize in roundly shaped grain-like structure with grain size of about 100 nm. The Er3+ photoluminescence response was obtained for all the films by excitation through cross-relaxation of Yb3+ ions. The IR emission spectrum, consisting of two narrow peaks at 1415 and 1514 nm, differs from the typical spectra of Er-doped materials. The VIS emission spectrum observed in as-deposited films does not appear after implantation and subsequent 900 °C annealing. © 2007 Elsevier B.V. All rights reserved., This work was supported in part by EU project NANOPHOS, Contract IST-2001-39112 and by the Bulgarian Ministry of Education and Science under Contract MUF-1511.

Optically active Er3+:Yb3+ codoped Y 2O3 films have been produced on c-cut sapphire substrates by pulsed laser deposition from ceramic Er:Yb:Y2O3 targets having different rare-earth concentrations. Stoichiometic films with very high rare-earth concentrations (up to 5.5 × 1021 at cm - 3) have been achieved by using a low oxygen pressure (1 Pa) during deposition whereas higher pressures lead to films having excess of oxygen. The crystalline structure of such stoichiometric films was found to worsen the thicker the films are. Their luminescence at 1.53 μm and up-conversion effects have been studied by pumping the Yb3+ at 0.974 μm. The highest lifetime value (up to 4.6 ms) is achieved in films having Er concentrations of ≈ 3.5 × 1020 at cm- 3 and total rare-earth concentration ≈ 1.8 × 1021 at cm- 3. All the stoichiometric films irrespective of their rare-earth concentration or crystalline quality have shown no significant up-conversion. © 2005 Elsevier B.V. All rights reserved., This work has been partially supported by the EU project NANOPHOS (Contract IST-2001-39112), by the Bulgarian National Science Foundation (Contract MUF-02/05), by the Spanish Ministry of Education and Science (Project MAT2000-1135-C02-02) and by the CSIC-Bulgarian Academy of Sciences bilateral cooperation program.

The authors regret that the following text needs to be revised for clarity: “In particular, panels (c) and (d) in Fig. 7 report zoomed (120 nm × 120 nm) AFM images of characteristic NPs observed in the case of the bulk target (c) and thin film (d), respectively, and the corresponding height profile, from which one can appreciate the noteworthy change of the NP height in the two cases.” The following text is submitted as the revision: Fig. 7 “Panels (c) and (d) show a zoomed (120 nm× 120 nm) portionwith characteristic NPs observed in the case of the bulk target and thin film, respectively, and the corresponding height profile”. The authors would like to apologise for any inconvenience caused.