Surface Modification of Metallic Targets with Ultrashort Laser Pulses

Interaction of pulsed femtosecond Ti:sapphire laser (160 fs), operating at high repetition rate (75 MHz) at 800 nm, with nickel-based superalloy Inconel 600 and tungsten-titanium (WTi) target was studied. The WTi target was in form of thin film deposited on silicon substrate. Low laser fluence of maximum 50 mJ/cm(2) had modified the target surface during irradiation/exposure time of seconds or minutes. The radiation absorbed from the laser beam generates at the surface a series of effects, such as direct material vaporization, formation of clusters, etc. Morphological features of the targets can be summarized as: (a) intensive removal of material and crater appearance; (b) creation of nanostructures; (c) microcracking, etc. Ablation of Inconel 600 surface is effective, resulting in formation of holes with small diameter ( LT = 10 mu m) and relatively large depth ( LT = 50 mu m). In case of WTi target/thin film, the surrounding rim is not so expressed, and crater depths are lower. It can be concluded that the average laser power of the order of watts, pulse energies of the order of nanojoules and high repetition rates (MHz range) can successfully modify metallic materials.International School and Conference on Photonics (PHOTONICA09), Aug 24-28, 2009, Belgrade, Serbi

Supplementary data for the article: Mancic, L.; Djukic-Vukovic, A.; Dinic, I.; Nikolic, M. G.; Rabasovic, M. D.; Krmpot, A. J.; Costa, A. M. L. M.; Marinkovic, B. A.; Mojovic, L.; Milosevic, O. One-Step Synthesis of Amino-Functionalized up-Converting NaYF 4 :Yb,Er Nanoparticles for: In Vitro Cell Imaging. RSC Advances 2018, 8 (48), 27429–27437. https://doi.org/10.1039/c8ra04178d

Supplementary material for: [https://doi.org/10.1039/c8ra04178d]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2225

Interactions of ultrashort laser pulses with hemoglobin: Photophysical aspects and potential applications

Hemoglobin (Hb), a life-sustaining and highly abundant erythrocyte protein, is not readily fluorescent. A few studies have already reported Two-Photon Excited Fluorescence (TPEF) of Hb, however, the mechanisms through which Hb becomes fluorescent upon interaction with ultrashort laser pulses are not completely understood. Here, we characterized photophysically this interaction on Hb thin film and erythrocytes using fluorescence spectroscopy upon single-photon/two-photon absorption, and UV-VIS single-photon absorption spectroscopy. A gradual increase of the fluorescence intensity, ending up with saturation, is observed upon prolonged exposure of Hb thin layer and erythrocytes to ultrashort laser pulses at 730 nm. When compared to protoporphyrin IX (PpIX) and oxidized Hb by H2O2, TPEF spectra from a thin Hb film and erythrocytes showed good mutual agreement, broad peaking at 550 nm, supporting hemoglobin undergoes degradation and that same fluorescent specie(s) originating from the heme moiety are generated. The uniform square shaped patterns of the fluorescent photoproduct exhibited the same level of the fluorescence intensity even after 12 weeks from the formation, indicating high photoproduct stability. We finally demonstrated the full potential of the formed Hb photoproduct with TPEF scanning microscopy towards spatiotemporally controlled micropatterning in HTF and single human erythrocyte labelling and tracking in the whole blood

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Supplementary data for the article: Mancic, L.; Djukic-Vukovic, A.; Dinic, I.; Nikolic, M. G.; Rabasovic, M. D.; Krmpot, A. J.; Costa, A. M. L. M.; Marinkovic, B. A.; Mojovic, L.; Milosevic, O. One-Step Synthesis of Amino-Functionalized up-Converting NaYF 4 :Yb,Er Nanoparticles for: In Vitro Cell Imaging. RSC Advances 2018, 8 (48), 27429–27437. https://doi.org/10.1039/c8ra04178d

Supplementary material for: [https://doi.org/10.1039/c8ra04178d]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2225

Photon diagnostics at the FLASH THz beamline

The THz beamline at FLASH, DESY, provides both tunable (1–300 THz) narrow-bandwidth (∼10%) and broad-bandwidth intense (up to 150 uJ) THz pulses delivered in 1 MHz bursts and naturally synchronized with free-electron laser X-ray pulses. Combination of these pulses, along with the auxiliary NIR and VIS ultrashort lasers, supports a plethora of dynamic investigations in physics, material science and biology. The unique features of the FLASH THz pulses and the accelerator source, however, bring along a set of challenges in the diagnostics of their key parameters: pulse energy, spectral, temporal and spatial profiles. Here, these challenges are discussed and the pulse diagnostic tools developed at FLASH are presented. In particular, a radiometric power measurement is presented that enables the derivation of the average pulse energy within a pulse burst across the spectral range, jitter-corrected electro-optical sampling for the full spectro-temporal pulse characterization, spatial beam profiling along the beam transport line and at the sample, and a lamellar grating based Fourier transform infrared spectrometer for the on-line assessment of the average THz pulse spectra. Corresponding measurement results provide a comprehensive insight into the THz beamline capabilities

Low and high repetition frequency femtosecond lasers processing of tungsten-based thin film

In this work we reported low and high repetition frequency femtosecond laser- induced modifications of tungsten-based thin film. The tungsten-titanium (WTi) thin film, thickness of 190 nm, was deposited by sputtering on single crystal Si (100) wafer. Irradiations were performed in air by linearly polarized and focused femtosecond laser beams with following parameters: (1) pulse duration 160 fs, wavelength 800 nm, laser repetition frequency (LRF) 75 MHz - high LRF, and (2) duration 40 fs, wavelength 800 nm, LRF of 1 kHz - low LRF. The results of femtosecond lasers processing of the WTi thin film revealed laser induced periodical surface structures (LIPSS) in the case of low LRF regime. LIPSSs were formed with different periodicity and different orientation to the laser polarization at the surface: micro-scale LIPSSs with orientation perpendicular to the laser polarization and nano-scale LIPSSs parallel and perpendicular to the laser polarization. After processing of the WTi/Si system in high LRF regime ablation and nanoparticles formation were registered

Time-Domain Spectroscopy for Space Exploration at Terahertz energy scales

In recent years, short pulse lasers have made massive progress and space-ready femtosecond laser systems are under development [1]. Moreover, employing time-domain spectroscopy techniques to identify planetary minerals by their spectroscopic fingerprints in the infrared and terahertz frequency range can have technological advantages over conventional spectroscopic techniques such as Fourier-Transform Infrared or Raman spectroscopy. The advantages are compactness, the possibility to replace bulky optical components by electro-optic/acousto-optic photonic techniques and the potential to be chip-integrable. We focus on one particular time-domain technique, coherent phonon spectroscopy (CPS), which is sensitive to Raman-active modes. Here, CPS is demonstrated in single-color operation and thus the simplicity and its insensitivity to fluorescence background add to the advantages of this technique

One-step preparation of gold nanoparticles - exfoliated graphene composite by gamma irradiation at low doses for photothermal therapy applications

Graphene is an excellent material to anchor metal nanoparticles due to its large surface area. In this paper, we report the use of electrochemically exfoliated graphene as support to anchor gold nanoparticles (Au NPs). Au NPs are synthesized via the reduction of chloroauric acid under gamma irradiation at low doses of 1, 5, and 10 kGy and directly deposited onto the graphene surface, making this procedure simple and fast. Good water dispersibility of exfoliated graphene, due to the presence of oxygen-containing functional groups in the structure of graphene, provides long-term stability of Au NPs - graphene composite dispersions. The majority of the Au NPs obtained by this method have sizes of up to 40 nm, while the increase in the applied dose leads to an increase in the amount of smaller nanoparticles. The increase of temperature of the prepared composite material upon irradiation with an 808 nm continuous wave laser was monitored. All samples show a temperature increase between 21.5 and 25.6 °C for 10 min of the laser exposure, which indicates that Au NPs - graphene composite can effectively be used in photothermal treatment for cancer therapy. © 2021 Elsevier Inc