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Influence of the pre-treatment of glass substrates on Laser-Induced Backside Wet Etching using NIR Nanosecond-Pulses and Cu-based solutions
Full text linkLaser induced backside wet etching (LIBWE) has shown to be a promising tool for the micro-structuring of transparent materials. Our group has investigated LIBWE using NIR ns-laser pulses and Cu-based absorber liquids. Focus of this paper is to investigate the influence of the pre-treatment of the transparent substrate on ablation. For this purpose experiments were done on untreated and silanized soda lime glass surfaces. Our results show that depending on the absorber liquid the silanization of the substrate either enhances or delays the ablation. Possible ablation models for the different experimental settings will be discussed
Laser Structuring of Glass-Carbon for Improvement of Its Emitting Properties
Full text linkLaser structuring as a stage of laser micromachining operations for a glass-carbon plate processing is described. The operations of laser scribing, milling, cleaning and marking were used for production of the field-emission multi-beam cathode preform. The operation of structuring was applied for production of micropeaks on the surface of the cathode beams. Two different approaches were tested for laser structuring of the cathode beams - linear scan and overlapping blind holes. The nanopeaks are self-organized in the process of the structuring. As a result we obtained a field-emission cathode with a high density of the current emission and a shorter technological route of its production
Electrical properties of ZnO:Al thin films fabricated by pulsed laser deposition method
Full text linkThe possibility of the high quality AZO thin films fabrication by the PLD method using the second harmonic of the Q-switched YAG:Nd3+ laser is demonstrated. The investigations of dependence of the AZO thin films properties on the PLD conditions (concentration of Al in the target, buffer gas pressure) have been conducted. The optimum conditions of the ZnO:Al thin films deposition have been defined
Microsurgery of Cell Membrane with Femtosecond Laser Pulses for Cell Fusion and Optical Injection
Full text linkWe report on results of using femtosecond laserscalpel for microsurgery of plasma membrane ofliving cells. Femtosecond laser pulses were appliedto initiate cell fusion as well as to performreversible permeabilization of cell membranerequired for efficient injection of extrinsicsubstances into the target cells. Laser-based cellfusion of mammalian embryo blastomeres as wellas fusion of cell bodies of neurons of molluskLymnaea stagnalis were successfully carried out byapplying single femtosecond laser pulses (secondharmonic of a Cr:Forsterite laser system) 620 nm,100 fs with the fluences of 0.42-0.71 J/cm2. It wasshown that the fusion of cells was completed within5-60 minutes depending on the cell type. Successfulpermeabilization of a cell membrane andoptoinjection of a membrane impermeable dye wasperformed with the help of a compact laser systemfor cell microsurgery DissCell-F (ytterbium laser,1050 nm, 75 MHz, ~115 fs). In both cases the laserirradiation parameters were thoroughly optimized toachieve high viability of treated cells and highefficiency of the procedures of cell fusion andoptical injection
Infrared broadband source from 1000nm to 1700nm, based on an Erbium, Neodymium and Bismuth doped double-clad fiber
Full text linkA Nd3+, Er3+ and Bi3+ doped double-clad fiber (core diameter of 25.5μm, cladding diameter of 125μm) with a broad infrared emission has been fabricated based on technique of dry granulated oxides and investigated. Upon the excitation with a 800nm cw pump source all of the three dopant materials showed fluorescence in the infrared region of interest (1000-1700nm). The observed emitted fluorescence power was measured to be 659μW. Changing the pump wavelength to 976nm led to a fluorescence of only Er3+ and Bi3+ and a broadening of the Bi3+ emission peak. The maximal measured fluorescence output power was 1.42mW, when pumped at 976nm
Enhancement of the Raman Scattering and the Third-Harmonic Generation in Silicon Nanowires
Full text linkWe studied features of Raman scattering and the third-harmonic generation in silicon nanowire (SiNW) ensembles formed by means of chemical etching of crystalline silicon (c-Si) wafers with preliminary deposited silver nanoparticles in hydrofluoric acid. The c-Si wafers of different crystallographic orientations and doping levels were used, which results in variations of the formed nanostructure size and degree of order. For the excitation at 1064 nm the ratio of Raman scattering signals for SiNWs and those for initial c-Si wafer ranges from 2 to 5, whereas for shorter wavelengths the ratio increases for more ordered arrays of SiNWs of greater diameter and decreases for less ordered SiNW structures. The TH signals in SiNW ensembles demonstrate both fall and one- or two-orders-of-magnitude rise in comparison with c-Si depending on the structure of the SiNW ensemble. The obtained results are explained by the effect of partial light localization in SiNW ensembles
Laser Microprinting of Transparent and Weakly Absorbing Solutions
Full text linkA laser-based technique for printing transparent andweakly absorbing liquids is developed. Its principleof operation relies in the tight focusing of shortlaser pulses inside the liquid and close to its freesurface, in such a way that the laser radiation isabsorbed in a tiny volume around the beam waist,with practically no absorption in any other locationalong the beam path. If the absorbed energyovercomes the optical breakdown threshold, acavitation bubble is generated, and its expansionresults in the propulsion of a small fraction of liquidwhich can be collected on a substrate, leading to theprinting of a microdroplet for each laser pulse. Thetechnique does not require the preparation of theliquid in thin film form, and its forward mode ofoperation imposes no restriction concerning theoptical properties of the substrate. We demonstratethat the technique is capable of printingmicrodroplets with good resolution, reproducibilityand control, and analyze the influence of the mainprocess parameters. The mechanisms of liquidprinting are also investigated: time-resolvedimaging provides a clear picture of the dynamics ofliquid transfer which allows understanding the mainfeatures observed in the printed droplets
Numerical reconstruction of 3D image in Fourier domain confocal optical coherence microscopy
Full text linkAlong with high longitudinal resolution of optical coherence tomography, confocal optical coherence microscopy (OCM) provides high transversal resolution due to relatively high numerical apertures. However, the presence of relatively high numerical apertures leads to limited depth of field, which reduces the speed of OCM and decreases the advantage of Fourier domain detection. In this paper we propose a numerical processing technique for three-dimensional image reconstruction in Fourier domain OCM. It takes into account not only the defocus of different parts of imaged volumetric sample, but also the effects of upper layers’ refractive index on imaging the sample inner structure. Besides providing sharp coherence gated imaging, this technique also allows for determining both the geometrical thickness and refractive index of the sample layers
Signal Enhancement in Disperse Solutions for the Analysis of Biomedical Samples by Photothermal Spectroscopy
Full text linkPhotothermal lens spectrometry not only shows high sensitivity of colored heme protein determination, but also provides a change in the sensitivity compared to the theoretical values due to changes in the heat transfer in dispersed media. This can be used for estimating the size of disperse particles exemplified by hemoglobin cyanide, photothermal examination of the state of existence of hemoglobin in highly saline solutions by changes in photothermal properties upon dissociation of hemoglobin tetramers into dimers and monomers. The example of determination of contrast agents (dyes) in blood as the versification of the platform of photoacoustic/photothermal measurement of circulating blood volume is shown
Application of Photothermal and Photoacoustic Spectroscopy for the Monitoring of Aqueous Dispersions of Carbon Nanomaterials
Full text linkPhotothermal and optoacoustic spectroscopy in their state-of-the-art techniques—multiwavelength, scanning and transient—are used for complex investigation and analysis (chemical analysis and the estimation of physicochemical properties and size) of novel carbon materials—fullerenes and nanodiamonds—and their aqueous dispersions as promising biomedical nanosystems. The estimation of the cluster size and the possibilities to determine subnanogram amounts of both nanodiamonds and fullerenes by these techniques are shown. The comparison of fullerene solutions in various solvents, toluene, N-methylpyrrolydone and water, is made. The advantages of the photothermal and optoacoustic techniques over conventional spectroscopies and the current limitation are discussed. The necessity to develop robust models for transient and imaging photothermal techniques is outlined
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