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The diffusion and activation of arsenic implanted into germanium at 40 keV with maximum concentrations below and above the solid solubility (8 x 1019 cm-3been studied, both experimentally and theoretically, after excimer laser annealing (λ = 308 nm) in the melting regime with different laser energy densities and single or multiple pulses. Arsenic is observed to diffuse similarly for different fluences with no out-diffusion and no formation of pile-up at the maximum melt depth. The diffusion profiles have been satisfactorily simulated by assuming two diffusivity states of As in the molten Ge and a non-equilibrium segregation at the maximum melt depth. The electrical activation is partial and decreases with increasing the chemical concentration with a saturation of the active concentration at 1 x 1020 cm-3, which represents a new record for the As-doped Ge system. [ABSTRACT FROM AUTHOR]

193-nm excimer laser interaction with ZnO single-crystal at 0.05-500KW/cm² intensities is investigated under ultra high vacuum conditions by time resolved photoluminescence (PL) spectroscopy. A dominant 3.18 eV PL emission band at 295K is observed. This band shows unusually long 0.52 ± 0.01 µs lifetime, indicating a defect mediated emission mechanism. The demonstrated negative thermal quenching for this band confirms its free electron to acceptor type transition. The involved acceptor is attributed to zinc vacancy with ~100 meV shallow acceptor state. This study finds that 193-nm interactions produce Zn vacancies in transient states at 0.05-50 KW/cm2 excitation intensities and in stable state at 500 KW/cm² or above intensities. The transient zinc vacancy production at such low intensities further validates the Frenkel pair creation as mechanism for creating these defects in ZnO single-crystal. [ABSTRACT FROM AUTHOR]

The production of gas phase atomic and ionic line spectra accompanying the high laser fluence irradiation of solid surfaces is well known and is most often due to the production and interaction of high densities of atoms, ions, and electrons generated from laser-induced breakdown. The resulting plasma expands and moves rapidly away from the irradiated spot and is accompanied by intense emission of light. This type of 'plume' is well studied and is frequently exploited in the technique of chemical analysis known as laser induced breakdown spectroscopy. Here, we describe a similar but weaker emission of light generated in vacuum by the laser irradiation of single crystal ZnO at fluences well below breakdown; this emission consists entirely of optical line emission from excited atomic Zn. We compare the properties of the resulting laser-generated gas-phase light emission (above and below breakdown) and describe a mechanism for the production of the low-fluence optical emission resulting from a fortuitous choice of material and laser wavelength. [ABSTRACT FROM AUTHOR]

We report mass-resolved time-of-flight measurements of neutral particles from the [formula] surface of single-crystal ZnO during pulsed 193-nm irradiation at laser fluences below the threshold for avalanche breakdown. The major species emitted are atomic Zn and O. We examine the emissions of atomic Zn as a function of laser fluence and laser exposure. Defects at the ZnO surface appear necessary for the detection of these emissions. Our results suggest that the production of defects is necessary to explain intense sustained emissions at higher fluence. Rapid, clean surface etching and high atomic zinc kinetic energies seen at higher laser fluences are also discussed. [ABSTRACT FROM AUTHOR]

Excimer Laser Annealing (ELA) with a wavelength of 248 nm is used to study doping of biaxialy compressively strained Si1-xGex/Si heterostructures. The challenge is to achieve a high activation of As in SiGe, while conserving the elastic strain and suppressing dopant diffusion. Doping of 20 nm Si0.64Ge0.36 layers by ion implantation of 1 × 1015 As+/cm2 and subsequent laser annealing using single 20 ns pulse with an energy density of 0.6 J/cm2 leads to an As activation of about 20% and a sheet resistance of 650 Ω/sq. At this laser energy density, the entire SiGe layer melts and the subsequent fast recrystallization on a nanosecond time scale allows high As incorporation into the lattice. Moreover, using these annealing parameters, the SiGe layer exhibits epitaxial regrowth with negligible strain relaxation. ELA at energy densities greater than 0.6 J/cm2 resembles Pulsed Lased Induced Epitaxy, leading to an intermixing of the SiGe layer with the Si substrate, thus to thicker single-crystalline strained SiGe layers with sheet resistance down to 62 Ω/sq. Effects of energy densities on composition, crystal quality, activation of As and co-doping with B are discussed and related to the spatial and temporal evolution of the temperature in the irradiated zone, as simulated by Finite Element Methods. [ABSTRACT FROM AUTHOR]

An experimental and theoretical study of the effect of excimer laser annealing (ELA) on B redistribution and electrical activation in Ge is reported. We performed detailed structural, chemical, and electrical characterizations of Ge samples implanted with B (20 keV, 1 × 1015, or 1 × 1016 B/cm2) and processed by ELA (λ = 308 nm) with multiple pulses (1, 3, or 10). We also developed a diffusion model, in order to simulate the B redistribution induced by the ELA process. We found an anomalous impurity redistribution in the molten phase, which causes a dopant incorporation during the melt-growth at the maximum melt depth. The investigated samples showed a partial electrical activation of the B dopant. The inactivation of B in the samples implanted with 1 × 1015 B/cm2 was correlated to an oxygen contamination, while the poor electrical activation of B in the samples implanted with 1 × 1016 B/cm2 was related to the precipitation of the dopant, in good agreement with the experimental and theoretical results. [ABSTRACT FROM AUTHOR]

Electric discharge excimer lasers are sustained in multi-atmosphere attaching gas mixtures that are typically preionized to enable a reproducible, uniform glow, which maximizes optical quality and gain. This preionization is often accomplished using UV light produced by a corona discharge within the plasma cavity. To quantify the relationship between corona discharge properties and those of the laser discharge, the triggering of electron avalanche by preionizing UV light in an electric discharge-pumped ArF* excimer laser was numerically investigated using a two-dimensional model. The preionizing UV fluxes were generated by a corona-bar discharge driven by the same voltage pulse as the main discharge sustained in a multi-atmospheric Ne/Ar/Xe/F2 gas mixture. The resulting peak photo-electron density in the inter-electrode spacing is around 108 cm-3, and its distribution is biased toward the UV source. The preionization density increases with increasing dielectric constant and capacitance of the corona bar. The symmetry and uniformity of the discharge are, however, improved significantly once the main avalanche develops. In addition to bulk electron impact ionization, the ionization generated by sheath accelerated secondary electrons was found to be important in sustaining the discharge current at experimentally observed values. At peak current, the magnitude of the ionization by sheath accelerated electrons is comparable to that from bulk electron impact in the vicinity of the cathode. [ABSTRACT FROM AUTHOR]

Cotton/polyester woven fabrics were functionalized with ZnO thin films or nanoparticles by pulsed laser deposition, using a KrF* excimer laser source. Depending on the number of applied laser pulses, well-separated nanoparticles (for 10 pulses) or compact thin films (for 100 pulses) were deposited. The synthesized nanostructures were evaluated morphologically by scanning electron microscopy and atomic force microscopy, physico-chemically by x-ray diffraction and functionally by the contact angle method. By modifying the ambient gas nature and pressure in the deposition chamber, hydrophilic or hydrophobic surfaces were obtained. When using an oxygen flux, both the deposited thin films and nanoparticles were hydrophilic. After deposition in vacuum, the nanoparticles were hydrophobic, but the thin films were super-hydrophobic. This radical modification of wetting behavior was assigned to the differences in microstructure features and surface electrical charging in the two cases. [ABSTRACT FROM AUTHOR]

Laser-induced fluorescence (LIF) of high-purity fused silica irradiated by ArF excimer laser is studied experimentally. LIF bands of the fused silica centered at 281 nm, 478 nm, and 650 nm are observed simultaneously. Furthermore, the angular distribution of the three fluorescence peaks is examined. Microscopic image of the laser modified fused silica indicates that scattering of the generated fluorescence by laser-induced damage sites is the main reason for the angular distribution of LIF signals. Finally, the dependence of LIF signals intensities of the fused silica on laser power densities is presented. LIF signals show a squared power density dependence, which indicates that laser-induced defects are formed mainly via two-photon absorption processes. [ABSTRACT FROM AUTHOR]

Nickel enhanced amorphous Si crystallization and silicidation on polyimide were studied during multipulse excimer laser annealing (ELA) from submelting to melting conditions. A ∼8 nm thick Ni film was deposited on a 100 nm thick α-Si layer at ∼70 °C in order to promote partial nickel diffusion into silicon. In the submelting regime, Ni atoms distributed during deposition in α-Si and the thermal gradient due to the presence of the plastic substrate were crucial to induce low fluence (≥0.08 J/cm2) Si crystallization to a depth which is strictly related to the starting Ni profile. Αmorphous-Si crystallization is not expected on pure Si at those low fluences. Additional pulses at higher fluences do not modify the double poly-Si/α-Si structure until melting conditions are reached. At a threshold of ∼0.2 J/cm2, melting was induced simultaneously in the polycrystalline layer as well as in the residual α-Si due to a thermal gradient of ∼200 °C. Further increasing the laser fluence causes the poly-Si layer to be progressively melted to a depth which is proportional to the energy density used. As a consequence of the complete Si melting, columnar poly-Si grains are formed above 0.3 J/cm2. For all fluences, a continuous NiSi2 layer is formed at the surface which fills the large Si grain boundaries, with the beneficial effect of flattening the poly-Si surface. The results would open the perspective of integrating Ni-silicide layers as metallic contacts on Si during α-Si-crystallization by ELA on plastic substrate. [ABSTRACT FROM AUTHOR]

We report time- and mass-resolved measurements of Si+ and O+ emission from ultraviolet-grade fused silica during exposure to pulsed 157 nm excimer laser radiation at fluences below the threshold for optical breakdown. The emission intensities are increased by treatments that increase the density of surface defects, such as abrasion, and are reduced by treatments that reduce the density of surface defects, such as annealing. Ion emission is a sensitive probe of mechanical damage on silica surfaces. The mean ion kinetic energies are typically several eV: 8–9 eV for Si+ and about 4 eV for O+. Hartree–Fock studies of candidate defect sites suggest that antibonding states excited by 157 nm photons play a critical role in the release of these ions. We propose that positive ion emission from fused silica under these conditions is best explained by a hybrid mechanism involving (a) the excitation of an antibonding chemical state (Menzel–Gomer–Redhead mechanism) and (b) the acceleration of the positive ion by repulsive electrostatic forces due to the photoionization of nearby electron traps. [ABSTRACT FROM AUTHOR]

We report mass-resolved time-of-flight measurements of neutral Si, O, and SiO from ultraviolet-grade fused silica during pulsed 157-nm irradiation at fluences well below the threshold for optical breakdown. Although the emission intensities are strongly affected by thermal treatments that affect the density of strained bonds in the lattice, they are not consistently affected by mechanical treatments that alter the density of point defects, such as polishing and abrasion. We propose that the absorption of single 157 nm photons cleave strained bonds to produce defects that subsequently diffuse to the surface. There they react with dangling bonds to release neutral atoms and molecules. Hartree–Fock calculations on clusters containing these defects support the contention that defect interactions can yield emission. More direct emission by the photoelectronic excitation of antibonding chemical states is also supported. [ABSTRACT FROM AUTHOR]

We report mass- and time-resolved measurements of negative ions produced by exposing fused silica to 157 nm radiation at fluences below the threshold for optical breakdown. The principal observed negative ions are O-, Si-, and SiO-, in order of decreasing intensity. The peak in the negative ion time-of-flight signals occurs after the peak in the positive ion signal and before the peak in the corresponding neutral atom or molecule signal. The negative ion intensities are strong functions of the degree of overlap between the positive ion and neutral atom densities. We propose that O-, Si-, and SiO- are created after the laser pulse, by electron attachment to these neutral particles and that the electrons participating in attachment events are trapped in the electrostatic potential of the positive ions. [ABSTRACT FROM AUTHOR]

The theoretical model of K9 glass irradiated by a 248-nm KrF excimer laser was established, and a numerical simulation was performed to calculate temperature and thermal stress fields in the K9 glass sample using the finite element method. The laser-induced damage thresholds were defined and calculated, and the effect of repetition frequency and the number of pulses on the damage threshold were also studied. Furthermore, the experiment research was carried out to confirm the numerical simulation. The damage threshold and damage morphology were analyzed by means of a metallurgical microscope and scanning electron microscopy. The simulation and experimental results indicated that the damage mechanism of K9 glass irradiated by a KrF excimer laser was melting damage and stress damage, and the stress damage first appeared inside the K9 glass sample. The tensile stress damage threshold, the compressive stress damage threshold, and the melting damage threshold were 0.64, 0.76, and 1.05 J/cm², respectively. The damage threshold decreased with increasing repetition frequency and number of laser pulses. The experimental results indicated that the damage threshold of K9 glass was 2.8 J/cm². [ABSTRACT FROM AUTHOR]

This letter presents SiC/Si diodes fabricated by the selective growth of SiC on Si substrate under ambient (atmospheric) conditions. The selective growth of \beta -SiC was obtained by irradiating a high-power KrF excimer laser beam on a polymethyl methacrylate (PMMA)-coated Si wafer. The laser decomposed carbon atoms from the PMMA, which dissolve into molten Si to form SiC. The Raman spectrum of the grown samples shows a dominant band in the range of 930–990 cm ^{-1} , i.e., the spectral region characteristic for \beta -SiC. The quality of SiC can be optimized by changing the induced power. The best performing SiC/Si diode shows a good rectification ratio of \sim 3 \times 10^4 (±1 V), a low leakage current density of \sim 1~\mu \textA /cm2 (−1 V), and high breakdown (>200 V), which confirms the high quality of the SiC/Si interface. The doping of SiC was calculated from 1/ C ^2 versus V plot and found to be \sim 5 \times 10^{15} cm ^{-3}$ . In addition, the measured photoelectric response shows a short circuit current density of 17 mA/cm2, an open circuit voltage of 0.33 V, and a fill factor of 62%. [ABSTRACT FROM PUBLISHER]

Any trauma can trigger a cascade of responses in tissues, with the purpose of safeguarding the integrity of the organ affected by the trauma and of preventing possible damage to nearby organs. Subsequently, the body tries to restore the function of the organ affected. The introduction of the excimer laser for keratorefractive surgery has changed the treatment landscape for correcting refractive errors, such as myopia, hyperopia, and astigmatism. In recent years, with the increased understanding of the basic science of refractive errors, higher-order aberrations, biomechanics, and the biology of corneal wound healing, a reduction in the surgical complications of keratorefractive surgery has been achieved. The understanding of the cascade of events involved in the corneal wound healing process and the examination of how corneal wound healing influences corneal biomechanics and optics are crucial to improving the efficacy and safety of laser vision correction. [ABSTRACT FROM AUTHOR]

Corrosion is an issue in Mg alloys resulting from chemical, and hence electrochemical, heterogeneity of alloy microstructures. In Mg alloy AZ31B-H24 (UNS M1 1311), Al8Mn5 intermetallic particles are dispersed throughout the matrix, forming micro-galvanic couples. Laser surface modification was performed in Ar and N2 environments with a pulsed excimer laser (λ = 248 nm, 25 ns full width at half maximum) with the aim of imparting chemical homogeneity on corrosion resistance. The results show the intermetallic particles can be partially or completely dissolved during lasing, resulting in a localized enrichment of Al and Mn in the matrix adjacent to the Al8Mn5 particles. In addition, thin oxide and nitride films were formed during processing, dependent on the processing gas used, not previously reported. Improved corrosion resistance at open circuit potential was observed for laser processed AZ3 1B, verified by electrochemical impedance spectroscopy and mass loss after immersion in 0.6 M NaCl. All processed samples showed a reduction in the H2 evolution reaction rate, as well as a reduction in growth of filiform-like corrosion surface coverage. The improvement was attributed to homogenization instead of film formation. Material characterization was performed by optical and electron microscopy, grazing incidence x-ray diffraction, and white light interferometry. [ABSTRACT FROM AUTHOR]

We report the fabrication of single wall carbon nanotubes (SWCNTs) by KrF excimer laser ablation under nitrogen atmosphere with a yield of over 70%. We used for the ablation process KrF excimer laser with a 20 ns pulse period and 30 Hz repetition rate, oven temperature 1100 °C, target composition: 0.6 at% Ni, 0.6 at% Co, 98.8 at% C (atomic percentage), 300 L/h nitrogen gas flow rate and a pressure of 500 Torr. Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) measurement results showed that the produced nanotubes have high length, narrow diameter distribution and contain low amount of amorphous carbon and metal catalyst particles. [ABSTRACT FROM AUTHOR]

Interaction of radiation with glasses often modifies their properties (e.g., the refractive index). Most noticeable is a loss in transmission. Such phenomena can be exploited in photo-sensitive materials, but have to be avoided in other applications. To improve the understanding of defect generation processes, a systematic comparison of defect formation in (fluoride-)phosphate glasses doped with low concentrations of 3d ions was attempted. Samples doped with 10-5000 ppm of Ti, V, Cr, Mn, Fe, Co, or Ni were irradiated in the UV range by excimer lasers. Defects, which generally form in the levels of several ppm, were characterized by optical and by electron spin resonance spectroscopy. V4+ was photo-oxidized to the empty valence shell d0 ion. Co2+, Mn2+, and Fe2+ were all photo-oxidized to the trivalent state while Ni2+ was photo-reduced. The fully oxidized Ti4+ was also photo-reduced. Cr3+ showed photo-disproportionation into Cr2+ and Cr6+. Qualitative and quantitative changes in defect formation rates depend not only on the ion, but also on the radiation parameters, for example, the wavelength of the excimer lasers used (193, 248, 351 nm) or the initial transmission of the glass samples at the chosen laser wavelength. Defect recovery was followed up to 10 years after the irradiation experiments. [ABSTRACT FROM AUTHOR]

The objective is to characterize the impact of different ablation parameters on the thermal load during corneal refractive surgery by means of excimer laser ablation on porcine eyes. One hundred eleven ablations were performed in 105 porcine eyes. Each ablation was recorded using infrared thermography and analyzed mainly based on the two tested local frequencies (40 Hz, clinical local frequency; 1000 Hz, no local frequency). The change in peak corneal temperature was analyzed with respect to varying ablation parameters [local frequency, system repetition rate, pulse energy, optical zone (OZ) size, and refractive correction]. Transepithelial ablations were also compared to intrastromal ablations. The average of the baseline temperature across all eyes was 20.5°C ± 1.1 (17.7°C to 22.2°C). Average of the change in peak corneal temperature for all clinical local frequency ablations was 5.8 °C ± 0.8 (p = 3.3E - 53 to baseline), whereas the average was 9.0°C ± 1.5 for all no local frequency ablations (p = 1.8E - 35 to baseline, 1.6E - 16 to clinical local frequency ablations). A logarithmic relationship was observed between the changes in peak corneal temperature with increasing local frequency. For clinical local frequency, change in peak corneal temperature was comparatively flat (r²=0.68 with a range of 1.5°C) with increasing system repetition rate and increased linearly with increasing OZ size (r² = 0.95 with a range of 2.4°C). Local frequency controls help maintain safe corneal temperature increase during excimer laser ablations. Transepithelial ablations induce higher thermal load compared to intrastromal ablations, indicating a need for stronger thermal controls in transepithelial refractive procedures. [ABSTRACT FROM AUTHOR]

A linear optical trap for circulating high power laser pulses and tuning these pulses to high repetition frequency of several tens of MHz has been developed. A ns excimer pumped dye laser pulse has been injected with help of a Wollaston prism and a synchronized Pockels cell into an optical trap formed by two highly reflecting mirrors in a linear configuration. The test was done at λ = 580 nm, but the optical trap can be used without limitations in a broad band of optical wavelengths (400-700 nm). Power considerations give an increase of the efficiency of the optical trap of about 7 times compared to single passage of the laser pulse through the experimental section. The time structure of the trapped laser pulses can be controlled by changing the distance between the two high reflecting mirrors. The efficiency of the optical trap strongly depends upon optical losses. To compensate the optical losses, an amplifying cell was introduced, and the efficiency was about 60 times higher than that by single passage of the laser pulse through the experimental section. [ABSTRACT FROM AUTHOR]

Conventional phototherapy uses a whole body cabinet or body part machines for the hand, foot or scalp. It has many disadvantages, due to which new phototherapy techniques have been developed. These new techniques are called targeted phototherapy. They include excimer laser, the intense pulse light (IPL) system, photodynamic therapy, and an ultraviolet (UV) light source with a sophisticated delivery system which is easy to operate by hand. The mechanisms of action of targeted phototherapy systems are similar to those in conventional UVB/UVA therapy. They have many advantages including lower risk of side effects, avoidance of exposure of unnecessary sites, faster response, and shorter duration of treatment. But they also have disadvantages such as high costs and inability to use them for extensive areas. This review article discusses targeted phototherapy, its mechanisms of action, and advantages and disadvantages in comparison to conventional phototherapy. [ABSTRACT FROM AUTHOR]

The effect of single-pulse plasma attenuation on a KrF excimer laser beam during irradiation of an Al 6061 alloy in ambient conditions was studied. The lowest attenuation was experimentally observed for a laser power density of 200 MW cm−2 per pulse, based on the material's surface roughness; the latter energy was determined as the critical point of the transition from an initial attenuation mode to the final one in a doubled stepped mechanism. Using a combination of profilometry and density functional theory, the second (high-energy) mode was determined as owing to a combination of plasma detachment and increased melt flow due to peak cavitation into the troughs created by the laser. The effect of energy absorption by the material's surface was modelled as the energy required to remove three crystal layers along the [001] direction of a pure Al alloy with a unit cell constant of 4·050 Å. [ABSTRACT FROM AUTHOR]

A model to achieve flat-top distribution of ultraviolet (UV) excimer laser is presented. Reserving the practically lossless superiority in the traditional diffraction approach, the method improves a diffraction grating with a controllable grating period based on the acousto-optic diffraction effect. A theoretical analysis extending the Huygens-Fresnel principle and Gauss Schell model describing a typically partial coherent source of excimer is proposed, so that a fast Fourier transform numerical simulation could be utilized to calculate the optimized Raman-Nath comprehensive parameter of the acousto-optic medium. Such an excimer homogenous technology could be wisely used in UV lithography and micromachining. [ABSTRACT FROM AUTHOR]

Protein phosphorylation is a ubiquitous post-translational modification, which often acts as a switch to proteins' activation and is frequently perturbed in diseases. Although many general phospho-protein detection tools are available, none of them offers information about the relative spatial arrangement of phosphorylated residues. Specifically, proximally phosphorylated residues are hallmarks of certain activated disease-relevant proteins. We herein report the first turn-on fluorescent sensor for the selective detection of proximally phosphorylated protein sites, suitable for application in both aqueous solutions and polyacrylamide gels. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition (PLD) is a very versatile tool to deposit thin films from a large variety of materials. Pulsed KrF excimer laser radiation at 248 nm wavelength can be employed to evaporate most oxide materials. Special focus has been put on transferring the stoichiometry of the target to the thin film, which is very important for complex oxides such as the cuprate high-temperature superconductors. For the multilayer deposition of superconducting devices highly reproducible thin films with controlled morphological and electronic properties are required. We report on methods of experimental design for the optimized deposition of YBa2Cu3O7−δ thin films on single crystalline oxide substrates. [ABSTRACT FROM AUTHOR]

State-of-the art pulsed UV excimer laser technology has a proven track record of stable performance under three-shift operation conditions in various industrial thin-film applications at stabilized pulse energy levels ranging from 100 to 1000 mJ per pulse. For the last 25 years excimer laser technology has formed the backbone of pulsed laser deposition advances. The available UV average power level nowadays exceeds 1 kW and novel excimer laser beam utilization schemes in combination with sophisticated substrate–target geometries are ready to utilize the full laser upscaling potential and thereby reduce unit costs. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition (PLD) is shown to be highly effective for growing plasmonic metal nanoparticle (PMN) films exhibiting strong surface plasmon resonance (SPR) under different process parameters. For PLD of PMN films the threshold fluences of ablation for the commonest plasmonic metals such as gold and silver are found to be in the range 1.3–1.6 J cm−2 using a KrF excimer laser. It is also found that the PLD-grown metal nanoparticle films generally have high packaging density of the nanoparticles, typically in the range 1010–1011 particles cm−2, which makes particles' shapes, particle–particle and particle–substrate interactions significant parameters for the ensuing plasmonic properties. The PLD is also shown to be a viable methodology of growing silver/gold alloy nanoparticle plasmonic films. The morphological and compositional characteristics of the metals and their alloy nanoparticle films are found to be controllable by the deposition parameters such as laser fluence, number of laser ablation pulses, target-to-substrate distance, substrate temperature and the gaseous ambience during the PLD or by the post-growth thermal annealing. These morphological and compositional characteristics in turn influence the plasmonic responses of the metal nanoparticle films, which enable one to vary the SPR wavelength typically in the spectral range of about 400–750 nm. The PMNs embedded in different dielectric layers with tuneable plasmon resonance characteristics, which can be grown effectively using PLD, appear to hold significant potential for the future photonic, photovoltaic and biomedical applications. [ABSTRACT FROM AUTHOR]

308nm xenon-chloride excimer laser, a novel mode of phototherapy, is an ultraviolet B radiation system consisting of a noble gas and halide. The aim of this systematic review was to investigate the literature and summarize all the experiments, clinical trials and case reports on 308-nm excimer laser in dermatological disorders. 308-nm excimer laser has currently a verified efficacy in treating skin conditions such as vitiligo, psoriasis, atopic dermatitis, alopecia areata, allergic rhinitis, folliculitis, granuloma annulare, lichen planus, mycosis fungoides, palmoplanar pustulosis, pityriasis alba, CD30+ lymphoproliferative disorder, leukoderma, prurigo nodularis, localized scleroderma and genital lichen sclerosus. Although the 308-nm excimer laser appears to act as a promising treatment modality in dermatology, further large-scale studies should be undertaken in order to fully affirm its safety profile considering the potential risk, however minimal, of malignancy, it may impose. [ABSTRACT FROM AUTHOR]

In this paper, the development is described of an efficient pyrene excimer signaling-based fluorescent sensor for the measurement of mercury ions in aqueous solutions based on thymine–Hg2+–thymine (T–Hg2+–T) coordination chemistry and the inclusion interaction of γ-cyclodextrin. Introduction of cyclodextrin can provide cooperation for the molecular level space proximity of the two labeled pyrene molecules, moreover the hydrophobic cavity of γ-cyclodextrin can also offer protection for the pyrene dimer's emission from the quenching effect of Hg2+ and enhance the fluorescence intensity of the pyrene excimer. To demonstrate the feasibility of the design, a bis-pyrene-labeled thymine-rich DNA strand was used as the detection probe. In the presence of Hg2+, stem-close-shaped DNA strands can be formed with the cooperation of γ-cyclodextrin and ideally predominantly emit the excimer fluorescence. The selectivity of the sensor for Hg2+ against other biologically and environmentally related metal ions is outstanding due to the high specificity of T–Hg2+–T formation. In addition, the pyrene excimer has a long fluorescence lifetime, which can tolerate intense background fluorescence interference from complex biological components, making it potentially applicable in the analysis of complex biological samples. [ABSTRACT FROM AUTHOR]

Abstract: Implantable microelectrodes provide a measure to electrically stimulate neurons in the brain and spinal cord and record their electrophysiological activity. A material with a high charge capacity such as activated or sputter-deposited iridium oxide film (AIROF or SIROF) is used as an interface. The Utah electrode array (UEA) uses SIROF for its interface material with neural tissue and oxygen plasma etching (OPE) with an aluminium foil mask to expose the active area, where the interface between the electrode and neural tissue is formed. However, deinsulation of Parylene-C using OPE has limitations, including the lack of uniformity in the exposed area and reproducibility. While the deinsulation of Parylene-C using an excimer laser is proven to be an alternative for overcoming the limitations, the iridium oxide (IrOx) suffers from fracture when high laser fluence (>1000mJ/cm2) is used. Iridium (Ir), which has a much higher fracture resistance than IrOx, can be deposited before excimer laser deinsulation and then the exposed Ir film area can be activated by electrochemical treatment to acquire the AIROF. Characterisation of the laser-ablated Ir film and AIROF by surface analysis (X-ray photoelectron spectroscopy, scanning electron microscope, and atomic force microscope) and electrochemical analysis (electrochemical impedance spectroscopy, and cyclic voltammetry) shows that the damage on the Ir film induced by laser irradiation is significantly less than that on SIROF, and the AIROF has a high charge storage capacity. The results show the potential of the laser deinsulation technique for use in high performance AIROF-coated UEA fabrication. [Copyright &y& Elsevier]

All dielectric high-reflectance (HR) mirror coatings consisting of AlF3/LaF3/oxide layers were deposited on deep-ultraviolet-grade fused silica and CaF2. A novel technique was employed to measure the absorption of these mirrors during irradiation by a 193-nm ArF excimer laser source. The method involves the application of a photothermal measurement technique. The setup uses a Shack--Hartmann wavefront sensor to measure wavefront deformation caused by the heating of the coating by the ArF beam. Laser calorimetric measurements of absorption were used to calibrate the wavefront sensor. The new test setup was used to investigate HR mirror coatings both before and after exposure to high average power ArF laser beams. HR mirror samples were irradiated by a 193-nm kilohertz laser source for either 500 million or 18.6 billion pulses. The differences between wavefront distortion measured inside the beam footprint compared to measured outside the beam footprint can be explained by compaction of the coating in the area heated by the ArF laser. Interesting wavefront-distortion results from testing mirrors with either fused silica or CaF2 substrates can be explained by considering the figure of merit of these materials for excimer-laser mirror substrates. [ABSTRACT FROM AUTHOR]

Background Combination of riboflavin/UVA cross-linking (CXL) and excimer laser ablation is a promising therapy for treating corneal ectasia. The cornea is strengthened by cross-linking, while the irregular astigmatism is reduced by laser ablation. This study aims to compare the efficacy of excimer laser ablation on porcine corneas with and without cross-linking. Methods and Findings The porcine cornea was de-epithelialized and treated with 0.1% riboflavin solution for 30 minutes. A half of the cornea was exposed to UVA-radiation for another 30 minutes while the controlled half of the cornea was protected from the UVA using a metal shield. Photo therapeutic keratectomy (PTK) was then performed on the central cornea. Corneal thickness of 5 paired locations on the horizontal line, ±0.5, ±1.0, ±1.5, ±2.0, and ±2.5 mm from the central spot, were measured using optical coherence tomography prior to and after PTK. The ablation depth was then determined by the corneal thickness. There was a 9% difference (P<0.001) in the overall ablation depth between the CXL-half corneas (158±22 µm) and the control-half corneas (174±26 µm). The ablation depths of all 5 correspondent locations on the CXL-half were significantly smaller (P<0.001). Conclusion The efficacy of the laser ablation seems to be lower in cross-linked cornea. Current ablation algorithms may need to be modified for cross-linked corneas. [ABSTRACT FROM AUTHOR]

AlGaN/GaN HEMTs grown on both-side-polished sapphire substrates were successfully lifted-off with a 193-nm UV excimer laser system. The photon energy of the 193 nm laser is larger than the band gap of AlN and thus it can be used to lift-off AlGaN HEMT structures with AlN or AlGaN interfacial layers grown on sapphire substrates prior to growth of the GaN buffer layers. The lifted-off HEMT chip was warped and showed 25-42% reduction of the saturation drain current. There was no degradation observed either in the forward or reverse gate current-voltage (I-V) characteristics or on the drain punch-through voltage. Based on comparisons of cross-sectional electron micrographs, no additional dislocations were created in the HEMT structures after the laser lift-off process. Reduction in saturation drain current was attributed to relaxation of the lifted-off HEMT structures. Newton's rings and Raman spectrum E2 peak shifts were used to estimate the strain relaxation of the laser lifted-off samples. [ABSTRACT FROM AUTHOR]

The effects of KrF excimer laser irradiation (248 nm) on aqueous suspensions of multiwalled carbon nanotubes (MWCNTs) were experimentally examined. MWCNTs and sodium dodecyl sulfate were added to deionized water at a mass fraction of 0.5 %, and the suspension was ultrasonicated for 30 min. Transmission electron microscopy (TEM) images of the nanotube samples after laser irradiation indicated fractures and network disentanglement. The laser fluence affected the thermal conductivity and viscosity of the suspensions beyond a threshold of 50 mJ · cm. As the irradiation time progressed at a laser fluence of 144 mJ · cm, the thermal conductivity and viscosity decreased until they reached saturation. The thermal-conductivity enhancement decreased from 16 % to 5 %, and the low shear viscosity decreased dramatically to 1/200 the shear viscosity of the non-irradiated sample. Raman spectra and TEM images showed that the defects in the nanotubes increased upon laser irradiation. In conclusion, excimer laser irradiation of a suspension of MWCNTs provided an effective way to tune the heat transfer and rheological characteristics of suspensions. [ABSTRACT FROM AUTHOR]

High surface area, sol-gel derived macroporous silica films doped with gold nanoparticles (AuNP) are used as a platform for high-density affinity-based immobilization of functional structure-switching DNA aptamer molecules onto Michelson interferometer long-period grating (LPG) fiber sensors, allowing for label-free detection of small molecular weight analytes such as adenosine triphosphate (ATP). The high surface area afforded by the sol-gel derived material allowed high loading of DNA aptamers, while the inclusion of gold nanoparticles within the silica film provided a high refractive index (RI) overlay, which is required to enhance the sensitivity of the LPG sensor according to our numerical simulations. By using a structure-switching aptamer construct that could release an oligonucleotide upon binding of ATP, the effective change in RI was both enhanced and inverted (i.e., binding of ATP caused a net reduction in molecular weight and refractive index), resulting in a system that prevented signals originating from nonspecific binding. This is the first report on the coupling of aptamers to LPG fiber sensors and the first use of high RI AuNP/silica films as supports to immobilize biomolecules onto the LPG sensor surface. The dual functionality of such films to both improve binding density and LPG sensor cladding refractive index results in a substantial enhancement in the sensitivity of such sensors for small molecule detection. [ABSTRACT FROM AUTHOR]

Previous work has demonstrated the ability to grow extremely high quality Tl/sub 0.5/Pb/sub 0.5/Sr/sub 1.6/Ba/sub 0.4/Ca/sub 2/Cu/sub 3/O/sub x/ epitaxial films up to 15 /spl mu/m thick using melt growth techniques on single crystal LaAlO/sub 3/ substrates. This melt growth process is an ideal candidate for producing high quality superconducting films on flexible metal substrates with textured buffer layers; however, the textured buffer layer of choice, cubic yttria stabilized zirconia (YSZ), appears to be incompatible with the melt growth of TI-Pb-Sr-Ba-Ca-Cu-O films. In this work, we investigate textured buffer layers which are compatible with the epitaxial growth of Tl/sub 0.5/Pb/sub 0.5/Sr/sub 1.6/Ba/sub 0.4/Ca/sub 2/Cu/sub 3/O/sub x/ films. Crucial properties for the successful development of a suitable buffer layer are lattice matching, chemical stability and texture. Buffer layer materials investigated are CeO/sub 2/ and LaAlO/sub 3/ grown using a UV (248 nm) pulsed excimer laser deposition system equipped with multiple targets and a controlled ambient. Influence of substrate temperature and ambient gas pressure and flow on buffer growth are analyzed via XRD characterization. Highly textured buffer layers have been fabricated. [ABSTRACT FROM PUBLISHER]

We report self-assembly of periodic surface structures in a commercial block copolymer (BCP) (Filofocon A) upon irradiation with a few tens of excimer laser pulses (20 ns, 193 nm) at fluences above the ablation threshold. This new type of structures is characterized by much larger periods than those characteristic for Laser-Induced Periodic Surface Structures (LIPSS) and features nanochains instead of ripples. We find a period of 790 nm at 400 mJ/cm2, scaling linearly with laser fluence up to a maximum of 1.0 μm. While an entangled random network of nanochains is produced for normal-incidence and non-polarized light, nanochain alignment can be achieved either by irradiation at an angle or by using linearly polarized light, forming a lamella-like structure. In both cases, the nanochains are aligned parallel to the penetrating polarization orientation and their period does not show a dependence on the angle of incidence, as opposed to the general behavior of standard LIPSS. Also, our results show that the chains are not formed by frozen capillary waves. In contrast, we show analogies of the nanochains produced to lamellar structures fabricated on a smaller scale in other BCP. We discuss the origin of the self-assembly process in terms of a combination of chemical (BCP), optical (surface scattering), and thermal (melting, coarsening, and ablation) effects. [ABSTRACT FROM AUTHOR]

The effect of excimer laser spot size on carbon laser-produced plasma dynamics is investigated. From intensified charged coupled device fast imaging, at higher fluences, an unusual plume shape was observed, the laser crater effects leading to an arrow like plume geometry. The origin of such behavior was explained through the laser-created crater profile measurements and space-resolved optical emission spectroscopy. [ABSTRACT FROM PUBLISHER]

The article discusses various reports published within the issue, including one on excimer lasers driving the semiconductor industry, one on quantum cascade lasers becoming a valuable source of mid-infrared and terahertz radiation, and one on semiconductor lasers revolutionizing telecommunications.

The article discusses a study which investigated a new generation of excimer laser which safely corrects myopia and myopic astigmatism with few complications. The focus of the study was the WaveLight Allegretto Wave Eye-Q excimer laser system used to perform PRK and LASIK. Results of the study were presented by Doctor Esmeralda Costa at the European Society of Cataract and Refractive Surgeons.