Low-order harmonic generation in a ZnS laser ablation plasma

Low-order (3rd to 9th) harmonic generation of a near-infrared driving laser (1064 nm) is reported in a laser ablation plasma of ZnS. Temporal analysis shows two distinct components with respect to the ablation event. The late temporal component exhibits high conversion efficiency for the highest harmonic orders observed. This is attributed to a dramatic modification of the plasma medium with the driving laser.Peer Reviewe

Spectroscopic assessment of the UV laser removal of varnishes on paint substrates

TECHNART 2015 − Catania, April 27 - 30, 2015; http://technart2015.lns.infn.it/The removal/thinning of aged varnishes from easel paintings is a very complex issue, which involves the need of finely-optimized conservation treatments for preserving both the pictorial substrates and the remaining varnish film. To this goal, cleaning techniques based on laser ablation may satisfy these requirements, especially when wavelengths and pulse durations are accurately selected. Recently, with the aim of minimizing photo-thermal, photo-mechanical and photo-chemical phenomena, ultra-short lasers operating in picosecond and femtosecond regimes have been introduced in the field [1-2]. Processing of fresh mastic and dammar varnishes with 248 nm, 500 fs laser pulses results in an improved etched morphology as compared with ns pulses of the same wavelength [1]. Irradiation of shellac at 213 nm with pulses of 15 ns of photo-sensitive tempera paint models covered with shellac allows controlled micrometric removal without affecting the surface morphology and chemical composition of the remaining varnish film and underlying paint layers. However, fs multiple pulse Ti:Sapphire irradiation of films of this varnish at 795, 398 and 265 nm has turned out to be ineffective for removing shellac varnish from egg-yolk based tempera paints [2]. Taking advantage from the latest findings, in the present work we focus on the assessment of the chemical and physical modifications induced by laser irradiation of varnish samples (i.e. dammar, mastic, shellac, mastic-oil) after natural and artificial ageing by using confocal ¿-Raman and laser induced fluorescence spectroscopies. We irradiated the varnish films with the fifth (213 nm) and fourth (266 nm) harmonics of a pulsed nanosecond (15 ns) Q-switched Nd:YAG laser. Together with systematic microscopy inspection of the irradiated areas, a significant effort was devoted to the study of the optical properties of the varnish films by means of UV-Vis absorption spectroscopy, which allowed the determination of linear absorption coefficients at the laser irradiation wavelengths used. Single-pulse laser ablation thresholds were measured by applying the spot regression method and processing of the films was carried out using three different scanning speeds that resulted in 1, 5 and 10 laser pulses on each irradiated area. The obtained results, using fluences well above the single-pulse ablation threshold of the treated varnishes, depend crucially on the irradiation wavelength, the considered varnish and its degree of polymerization. In contrast with the induced modifications resulting from irradiation at 266 nm, that lead to a whitish appearance (indicative of bubble formation) and discoloration of pigments, the promising results achieved at 213 nm emphasize the importance of using a highly absorbed wavelength to finely remove the oxidized uppermost layer of different types of aged varnishes. [1] Pouli, P., Paun, I. A., Bounos, G., Georgiou, S., Fotakis, C., Applied Surface Science, 254(21), 2008, 6875-6879. [2] Oujja, M., García, A., Romero, C., de Aldana, J. R. V., Moreno, P., Castillejo, M., Physical Chemistry Chemical Physics, 13(10), 2011, 4625-4631.Peer Reviewe

Gold coating of micromechanical DNA biosensors by pulsed laser deposition

In this work, we describe the gold-coating of silicon microcantilever sensors by pulsed laser deposition (PLD) and their performance as DNA biosensors. To test optimum deposition conditions for coating the sensors, silicon substrates were gold coated by PLD using the fifth harmonic of a Nd:YAG laser (213 nm, pulse duration 15 ns). The gold deposits were characterized by atomic force microscopy and x-ray diffraction. The adequate conditions were selected for coating the sensors with a 20 nm thick gold layer and subsequently functionalized with a self-assembled monolayer of thiolated DNA. To verify PLD as a tool for gold coating of biomechanical sensors, they were characterized by using a scanning laser analyzer platform. Characterization consisted in the measurement of the differential stress of the cantilevers upon hydration forces before and after functionalization with a double-stranded DNA monolayer. The measurements showed that the sensor surface stress induced by the adsorption of water molecules is approximately seven times higher than that of functionalized sensors gold coated by thermal evaporation. These results indicate that gold coating by PLD could be an advantageous method to enhance the response of biomechanical sensors based on gold-thiol chemistry.Peer Reviewe

Harmonic generation by atomic and nanoparticle precursors in a ZnS laser ablation plasma

Harmonic generation of a driving laser propagating across a laser ablation plasma serves for the diagnosis of multicomponent plumes. Here we study the contribution of atomic and nanoparticle precursors to the generation of coherent ultraviolet and vacuum ultraviolet light as low-order harmonics of the fundamental emission (1064 nm) of a Q-switched Nd:YAG laser in a nanosecond infrared ZnS laser ablation plasma. Odd harmonics from the 3rd up to the 9th order (118.2 nm) have been observed with distinct temporal and spatial characteristics which were determined by varying the delay between the ablation and driving nanosecond pulses and by spatially scanning the plasma with the focused driving beam propagating parallel to the target. At short distances from the target surface (≤1 mm), the harmonic intensity displays two temporal components peaked at around 250 ns and 10 μs. While the early component dies off quickly with increasing harmonic order and vanishes for the 9th order, the late component is notably intense for the 7th harmonic and is still clearly visible for the 9th. Spectral analysis of spontaneous plume emissions help to assign the origin of the two components. While the early plasma component is mainly constituted by neutral Zn atoms, the late component is mostly due to nanoparticles, which upon interaction with the driving laser are subject to breakup and ionization. With the aid of calculations of the phase matching integrals within the perturbative model of optical harmonic generation, these results illustrate how atom and nanoparticle populations, with differing temporal and spatial distributions within the ablation plasma, contribute to the nonlinear medium.Funding has been provided by Ministerio de Economía y Competitividad (MINECO) of Spain under Project CTQ2013-43086-P. I.L-Q., A.B-C. and M.O. thank respectively MINECO, for a FPI fellowship (BES-2011-044738), CSIC, for a JAE-TEC 2010 contract and CSIC for a contract. Fruitful discussions with Dr. Mikel Sanz and Prof. A. Gonzalez-Arroyo are acknowledged.Peer reviewe

Laser nanostructuring of polymers: Ripples and applications

Polymer nanostructures and nanopatterns are being profusely used for developing next-generation organic devices with analytical and biological functions and photonic applications. Laser based strategies constitute an advantageous approach for the assembly and control of this type of soft matter nanostructures as they afford the sought versatility and reliability. Recent and on-going research on laser nanostructuring of thin films of synthetic polymers and natural biopolymers will be exemplified by studies on the generation of laser induced periodic surface structures (LIPSS) and their use for surface enhanced Raman spectroscopy (SERS) based sensors. © 2012 American Institute of PhysicsFunded by MICINN, Spain, Projects CTQ2010-15680 and MAT2009-07789. MICINN, Spain, Juan de la Cierva contract and an FPI fellowshipPeer Reviewe

Femtosecond pulsed laser deposition of nanostructured CdS films

In this work, we report an investigation of the properties of nanostructured deposits obtained from femtosecond pulsed laser deposition of CdS sintered targets. Specifically, we address the effects of laser irradiation wavelength, laser fluence, and substrate temperature (from 25 to 450 °C). The composition of the deposits was characterized using X-ray photoelectron spectroscopy (XPS), their crystallinity by X-ray diffraction (XRD), and the surface morphology was studied by environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM). It has been found that the smallest nanoparticles, with an average diameter of 25 nm and a narrow size distribution, together with particulates in the range of 80-120 nm, are obtained at the shortest laser wavelength of 266 nm on room-temperature substrates. Deposits do not contain microscopic droplets in any of the explored conditions. © 2010 American Chemical Society.Peer Reviewe

UV, visible and IR laser interaction with gelatine

4p, 2fig.. -- EIGHTH INTERNATIONAL CONFERENCE ON LASER ABLATION (COLA'05) 11–16 September, 2005, Banff, CanadaIn this work we investigate the effects on gelatine films of nanosecond pulsed laser irradiation at different laser wavelengths from the UV to the IR at 248, 266, 355, 532 and 1064 nm. We compared gelatines differing in gel strength values (Bloom 75 and 225) and in crosslinking degree. Formation of bubbles at the wavelengths in the UV (248 and 266 nm), melting and resolidification at 355 nm, and formation of craters by ablation in the VIS and IR (532 and 1064 nm) are the observed morphological changes. On the other hand, changes of the fluorescence behaviour of the films upon UV irradiation reveal chemical modifications of photolabile chromophores. © 2007 IOP Publishing Ltd.Work funded by Project MCYT BQU2003-08531-C02-01. MO and ER thank CSIC I3P program; CA acknowledges CSIC-UCM-FE-FOTOFILM fellowship. We thank D.Varga (ICTP) for ESEM picture

Femtosecond laser deposition of TiO2 by laser induced forward transfer

Femtosecond lasers have been used for laser induced forward transfer (LIFT) of TiO2, a wide-band semiconductor with many industrial and research applications. TiO2 polycrystalline thin films on quartz (obtained by pulsed laser deposition) were used as donors and both quartz and fluorine-doped tin dioxide coated glass substrates as acceptors. LIFT was performed at the laser wavelengths of 248 and 800 nm with pulses of 450 and 300 fs respectively. The transferred material was characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction and micro-Raman spectroscopy to determine the composition and crystalline quality, and by scanning electron microscopy and atomic force microscopy to assess the surface morphology. The relation between these properties and the laser transfer conditions, including wavelength, pulse energy and acceptor substrate, are presented. © 2010 Elsevier B.V.Peer Reviewe

Laser photodissociation of ketene at 230 nm

Abstract˜1˜1 Ketene in a molecular beam is excited at the onset of its X A ™ B B absorption band by laser light at 230 nm. The For the latter, the PST calculations lead to an average rotational energy in CO which is not compatible with the measured value, thus suggesting that this channel does not represent an important contribution to the dissociation process. q 1998 Elsevier Science B.V. All rights reserved

Factores relacionados con la calidad de vida de los pacientes con enfermedad pulmonar obstructiva crónica

ResumenObjetivoDescribir la relación entre factores pronósticos, individuales o asociados en clasificaciones multidimensionales (BODE y ADO), y la calidad de vida relacionada con la salud (CVRS) de los pacientes con enfermedad pulmonar obstructiva crónica (EPOC).DiseñoEstudio descriptivo transversal.EmplazamientoAtención primaria.ParticipantesMuestreo aleatorizado sistemático de 102 pacientes diagnosticados de EPOC. Excluidos aquellos con exacerbación aguda, demencia, enfermedad terminal o los que reciben atención domiciliaria.Mediciones principalesDatos demográficos, hábito tabáquico, índice de masa corporal y número de exacerbaciones. Comorbilidad. Grado de disnea. Prueba de función respiratoria. Capacidad de ejercicio. El índice BODE y ADO. Cuestionario EuroQol-5D (EQ-5D) y escala visual analógica (EVA).ResultadosEn EQ-5D: movilidad, 43,9%; cuidado personal, 13,3%; actividades cotidianas, 29,6%; dolor/malestar, 55,1%; ansiedad/depresión, 37,8%. El 34,7% EVA ≤ 60%.Exacerbaciones: movilidad, OR: 1,85 (IC 95%: 1,08-3,20); cuidado personal, OR: 2,12 (IC 95%: 1,03-4,76); actividades cotidianas, OR: 2,35 (IC 95%: 1,17-4,71); EVA, coeficiente regresión: −3,50 (IC 95%: −6,31- −0,70). Disnea: movilidad, OR: 4,47 (IC 95%: 1,39-14,42); actividades cotidianas, OR: 7,71 (IC 95%: 2,03-12,34)]; EVA, coeficiente regresión: −7,15 (IC 95%: −11,71- −2,59).BODE: movilidad, OR: 1,53 (IC 95%: 1,15-2,02); cuidado personal, OR: 2,08 (IC 95%: 1,40-3,11); actividades cotidianas, OR: 1,97 (IC 95%: 1,38-2,80); EVA, coeficiente regresión: −3,96 (IC 95%: −5,51- −2,42). ADO: movilidad, OR: 2,42 (IC 95%: 1,39-4,20); cuidado personal, OR: 3,21 (IC 95%: 1,67-6,18); actividades cotidianas, OR: 3,17 (IC 95%: 1,69-5,93); EVA, coeficiente regresión: −3,53 (IC 95%: −5,57- −1,49).ConclusionesLos índices BODE y ADO presentaron una importante asociación con la CVRS. Las exacerbaciones y la disnea fueron los factores individuales que mejor se relacionaron con la CVRS.AbstractObjectiveTo describe the relationship between individual or combined prognostic factors in the multidimensional classifications (BODE and ADO), and health-related quality of life (HRQOL) in patients with chronic obstructive pulmonary disease (COPD).DesignCross-sectional descriptive study.SettingPrimary care.ParticipantsSystematic random sample of 102 patients diagnosed with COPD, excluding those patients with acute exacerbation, dementia, terminal illness or those who receive home care.Main measurementsDemographics variables, smoking habits, body mass index and number of exacerbations. Comorbidity. Degree of dyspnea. Respiratory function tests. Exercise capacity. The BODE index and the ADO index. The EuroQol-5D questionnaire (EQ-5D), and visual analogue scale (VAS).ResultsEQ-5D: mobility: 43.9%; personal care: 13.3%; daily-life activities: 29.6%; pain/discomfort: 55.1%; anxiety/depression: 37.8%, and 34.7% VAS ≤ 60%.Exacerbations: Mobility, OR: 1.85 (95%CI: 1.08-3.20); personal care, OR: 2.12 (95%CI: 1.3-4.76); daily-life activities, OR: 2.35 (95%CI: 1.17-4.71); VAS, regression coefficient: −3.50 (95%CI: 6.31- −0.70). Dyspnea: mobility, OR: 4.47 (95%CI: 1.39-14.42); daily-life activities, OR: 7.71 (95%CI: 2.03-12.34); VAS, regression coefficient: −7.15 (95%CI: 11.71- −2.59).BODE: mobility, OR: 1.53 (95%CI: 1.15-2.02); personal care, OR: 2.08 (95%CI: 1.40-3.11); daily-life activities, OR: 1.97 (95%CI: 1.38-2.80); VAS, regression coefficient: −3.96 (95%CI: −5.51- −2.42). ADO: mobility, OR: 2.42 (95%CI: 1.39-4.20); personal care, OR: 3.21 (95%CI: 1.67-6.18); daily-life activities, OR: 3.17 (95%CI: 1.69-5.93); VAS, regression coefficient: −3.53 (95%CI: −5.57- −1.49).ConclusionsThe BODE index and the ADO index showed a significant association with HRQOL. Exacerbations and dyspnea were the best individual factors related to HRQoL