Filamentation management by using programmable diffractive optical elements

Treball Final de Màster Universitari en Física Aplicada. Codi: SIN019. Curs acadèmic: 2015-201

Pulsed laser ablation in liquids for the production of gold nanoparticles and carbon quantum dots: from plasmonic to fluorescence and cell labelling

Ponència presentada a Smart Nanomaterials: Advances, Innovation and Applications (SNAIA 2019), celebrat a París els dies 10-13 de desembre de 2019The synthesis of high purity ligand free nanoparticles represents one of the requirements for nanotechnology application in highly relevant fields as nanomedicine and theranostics. Laser synthesis and processing of colloids permits the synthesis of ligand free nanoparticles with reduced impurities from bulk targets and colloidal dispersions. In the present contribution a novel approach for enhanced production of ligand free gold nanoparticles by femtosecond ablation of a bulk target is studied together with a more efficient synthesis of fluorescent carbon quantum dots from a colloidal suspension of carbon microparticles in polyethylene glycol

Femtosecond-laser-irradiation-induced structural organization and crystallinity of Bi2WO6

Controlling the structural organization and crystallinity of functional oxides is key to enhancing their performance in technological applications. In this work, we report a strong enhancement of the structural organization and crystallinity of Bi2WO6 samples synthetized by a microwave-assisted hydrothermal method after exposing them to femtosecond laser irradiation. X-ray difraction, UVvis and Raman spectroscopies, photoluminescence emissions, energy dispersive spectroscopy, feld emission scanning electron microscopy, and transmission electron microscopy were employed to characterize the as-synthetized samples. To complement and rationalize the experimental results, frstprinciples calculations were employed to study the efects of femtosecond laser irradiation. Structural and electronic efects induced by femtosecond laser irradiation enhance the long-range crystallinity while decreasing the free carrier density, as it takes place in the amorphous and liquid states. These efects can be considered a clear cut case of surface-enhanced Raman scattering

Green nanoparticle synthesis at scale : a perspective on overcoming the limits of pulsed laser ablation in liquids for high-throughput production

Nanoparticles have become increasingly important for a variety of applications, including medical diagnosis and treatment, energy harvesting and storage, catalysis, and additive manufacturing. The development of nanoparticles with different compositions, sizes, and surface properties is essential to optimize their performance for specific applications. Pulsed laser ablation in liquid is a green chemistry approach that allows for the production of ligand-free nanoparticles with diverse shapes and phases. Despite these numerous advantages, the current production rate of this method remains limited, with typical rates in the milligram per hour range. To unlock the full potential of this technique for various applications, researchers have dedicated efforts to scaling up production rates to the gram-per-hour range. Achieving this goal necessitates a thorough understanding of the factors that limit pulsed laser ablation in liquid (PLAL) productivity, including laser, target, liquid, chamber, and scanner parameters. This perspective article explores these factors and provides a roadmap for increasing PLAL productivity that can be adapted to specific applications. By carefully controlling these parameters and developing new strategies for scaling up production, researchers can unlock the full potential of pulsed laser ablation in liquids

Overcoming the barrier of nanoparticle production by femtosecond laser ablation in liquids using simultaneous spatial and temporal focusing

There exists an increasing demand of industrial-scale production of high-purity ligand-free nanoparticles due to the continuous development of biomedicine, catalysis, and energy applications. In this contribution, a simultaneous spatial and temporal focusing (SSTF) setup is first proposed for increasing nanoparticle productivity of the eco-friendly pulsed laser ablation in liquids (PLAL) technique. In spite of the fact that femtosecond pulses have proved to achieve higher ablation rates in air than picosecond pulses, in PLAL this is reversed due to the nonlinear energy losses in the liquid. However, thanks to the incorporation of SSTF, the energy delivered to the target is increased up to 70%, which leads to a nanoparticle production increase of a 2.4 factor. This breaks a barrier toward the employment of femtosecond lasers in high-efficiency PLAL

Diffractive control of 3D multifilamentation in fused silica with micrometric resolution

We show that a simple diffractive phase element (DPE) can be used to manipulate at will the positions and energy of multiple filaments generated in fused silica under femtosecond pulsed illumination. The method allows obtaining three-dimensional distributions of controlled filaments whose separations can be in the order of few micrometers. With such small distances we are able to study the mutual coherence among filaments from the resulted interference pattern, without needing a two-arm interferometer. The encoding of the DPE into a phase-only spatial light modulator (SLM) provides an extra degree of freedom to the optical set-up, giving more versatility for implementing different DPEs in real time. Our proposal might be particularly suited for applications at which an accurate manipulation of multiple filaments is required.We acknowledge support from Generalitat Valenciana through the programme PROMETEO-2012-021, University Jaume I through the project P1·1B2013-53, and Ministerio de Economía y Competitividad (MINECO) through the project FIS2013-40666-P. The authors are also very grateful to the SCIC of the Universitat Jaume I for the use of the femtosecond laser

Effects of femtosecond laser and other surface treatments on the bond strength of metallic and ceramic orthodontic brackets to zirconia

[EN]Femtosecond laser has been proposed as a method for conditioning zirconia surfaces to boost bond strength. However, metallic or ceramic bracket bonding to femtosecond lasertreated zirconia surfaces has not been tested. This study compared the effects of four conditioning techniques, including femtosecond laser irradiation, on shear bond strength (SBS) of metallic and ceramic brackets to zirconia.Three hundred zirconia plates were divided into five groups: 1) control (C); 2) sandblasting (APA); 3) silica coating and silane (SC); 4) femtosecond laser (FS); 5) sandblasting followed by femtosecond laser (APA+SC). A thermal imaging camera measured temperature changes in the zirconia during irradiation. Each group was divided into 2 subgroups (metallic vs ceramic brackets). SBS was evaluated using a universal testing machine. The adhesive remnant index (ARI) was registered and surfaces were observed under SEM. Surface treatment and bracket type significantly affected the bracket-zirconia bond strength. SBS was significantly higher (p APA > FS > SC > control) than metallic brackets (APA+FS > FS > SC > APA > control). For metallic brackets, groups SC (5.99 ± 1.86 MPa), FS (6.72 ± 2.30 MPa) and APA+FS (7.22 ± 2.73 MPa) reported significantly higher bond strengths than other groups (p < 0.05). For ceramic brackets, the highest bond strength values were obtained in groups APA (25.01 ± 4.45 MPa), FS (23.18 ± 6.51 MPa) and APA+FS (29.22 ± 8.20 MPa).Femtosecond laser enhances bond strength of ceramic and metallic brackets to zirconia. Ceramic brackets provide significantly stronger adhesion than metallic brackets regardless of the surface treatment method

Optical characterisation and photothermal conversion efficiency of a water-based carbon nanofluid for direct solar absorption applications.

Carbon nanoparticles are very useful in solar thermal applications as they absorb much of the solar spectrum and can be inexpensive. Water-based carbon nanofluids with two different concentrations (3 and 33 mg l−1) were prepared with sodium dodecyl sulphate as surfactant to achieve good high-temperature stability with a constant mean particle size of 200 nm at 25 °C and 85 °C. The morphology of the nanoparticles was observed by Transmission Electron Microscopy and the particle size distribution was studied using Dynamic Light Scattering at room and high temperature. Ballistic transmittance, absorption coefficient and scattering albedo of the three fluids were measured by a spectrophotometer with and without an integrating sphere using the Kubelka-Munk theory. The average value of the absorption coefficient showed important increases when comparing water against the nanofluid with the highest concentration (from 0.1 to 3.3 cm−1). Finally, the temperature change achieved when lighting the samples with an artificial sunlight simulator were measured and photothermal conversion efficiencies were evaluated, with increases of up to 200% when comparing nanofluid and base fluid. The results of this study show this kind of nanofluids to be very interesting for increasing the overall efficiency of the direct absorber solar collectors

Diffraction-Based Phase Calibration of Spatial Light Modulators With Binary Phase Fresnel Lenses

We propose a simple and robust method to determine the calibration function of phase-only spatial light modulators (SLMs). The proposed method is based on the codification of binary phase Fresnel lenses (BPFLs) onto an SLM. At the principal focal plane of a BPFL, the focal irradiance is collected with a single device just able to measure intensity-dependent signals, e.g., CCD camera, photodiodes, power meter, etc. In accordance with the theoretical model, it is easy to extract the desired calibration function from the numerical processing of the experimental data. The lack of an interferometric optical arrangement, and the use of minimal optical components allow a fast alignment of the setup, which is in fact poorly dependent on environmental fluctuations. In addition, the effects of the zero-order, commonly presented in the diffraction-based methods, are drastically reduced because measurements are carried out only in the vicinity of the focal points, where main light contributions are coming from diffracted light at the BPFL. Furthermore, owing to the simplicity of the method, full calibration can be done, in most practical situations, without moving the SLM from the original place for a given application.This work was supported in part from MINECO under Grant FIS2013–40666-P, Generalitat Valenciana under Grants PROMETEO2012–021 and ISIC 2012/013, and Universitat Jaume I (P1-1B2012-55)