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Testing of a femtosecond pulse laser in outer space.

ABSTRACT: We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future.

SUBMITTER: Lee J

PROVIDER: S-EPMC4038913 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Femtosecond-Laser-Pulse Characterization and Optimization for CARS Microscopy.

Project description:We present a simple method and its experimental implementation to determine the pulse durations and linear chirps of the pump-and-probe pulse and the Stokes pulse in a coherent anti-Stokes Raman scattering microscope at sample level without additional autocorrelators. Our approach exploits the delay line, ubiquitous in such microscopes, to perform a convolution of the pump-and-probe and Stokes pulses as a function of their relative delay and it is based on the detection of the photons emitted from an appropriate non-linear sample. The analysis of the non-resonant four-wave-mixing and sum-frequency-generation signals allows for the direct retrieval of the pulse duration on the sample and the linear chirp of each pulse. This knowledge is crucial in maximizing the spectral-resolution and contrast in CARS imaging.

| S-EPMC4880195 | biostudies-literature

Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation.

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| S-EPMC4904278 | biostudies-literature

Femtosecond Double-Pulse Laser Ablation and Deposition of Co-Doped ZnS Thin Films.

Project description:Nanostructured thin films of Co-doped zinc sulfide were synthesized through femtosecond pulsed laser deposition. The scheme involved ablation of physically mixed Co and ZnS with pairs of ultrashort pulses separated in time in the 0-300 ps range. In situ monitorization of the deposition process was carried out through a simultaneous reflectivity measurement. The crystallinity of generated nanoparticles and the inclusion of Co in the ZnS lattice is demonstrated by transmission electron microscopy and energy dispersive X-ray microanalysis (TEM-EDX) characterization. Surface morphology, Raman response, and photoluminescence of the films have also been assessed. The role of interpulse temporal separation is most visible in the thickness of the films obtained at the same total fluence, with much thicker films deposited with short delays than with individual uncoupled pulses. The proportion of Co in the synthesized doped ZnS nanoparticles is found to be substantially lower than the original proportion, and practically independent on interpulse delay.

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Designable Layer Edge States in Quasi-2D Perovskites Induced by Femtosecond Pulse Laser.

Project description:The low-energy layer edge states (LESs) from quasi 2D hybrid perovskite single crystals have shown great potential because of their nontrivial photoelectrical properties. However, the underlying formation mechanism of the LESs still remains controversial. Also, the presence or creation of the LESs is of high randomness due to the lack of proper techniques to manually generate these LESs. Herein, using a single crystals platform of quasi-2D (BA)2 (MA)n-1 Pbn I3n+1 (n > 1) perovskites, the femtosecond laser ablation approach to design and write the LESs with a high spatial resolution is reported. Fundamentally, these LESs are of smaller bandgap 3D MAPbI3 nanocrystals which are formed by the laser-induced BA escaping from the lattice and thus the lattice shrinkage from quasi-2D to 3D structures. Furthermore, by covering the crystal with tape, an additional high-energy emission state corresponding to the reformation of (BA)2 PbI4 (n = 1) within the irradiation region is generated. This work presents a simple and efficient protocol to manually write LESs on single crystals and thus lays the foundation for utilizing these LESs to further enhance the performance of future photoelectronic devices.

| S-EPMC9284193 | biostudies-literature

Controlling population of the molecular rotational state and the alignment theoretically by tailored femtosecond laser pulse.

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| S-EPMC5792930 | biostudies-literature

Femtosecond Single-Pulse and Orthogonal Double-Pulse Laser-Induced Breakdown Spectroscopy (LIBS): Femtogram Mass Detection and Chemical Imaging with Micrometer Spatial Resolution.

Project description:Femtosecond laser-induced breakdown spectroscopy (fs-LIBS) is employed to detect tiny amounts of mass ablated from macroscopic specimens and to measure chemical images of microstructured samples with high spatial resolution. Frequency-doubled fs-pulses (length 400 fs, wavelength 520 nm) are tightly focused with a Schwarzschild microscope objective to ablate the sample surface. The optical emission of laser-induced plasma (LIP) is collected by the objective and measured with an echelle spectrometer equipped with an intensified charge-coupled device camera. A second fs-laser pulse (1040 nm) in orthogonal beam arrangement is reheating the LIP. The optimization of the experimental setup and measurement parameters enables us to record single-pulse fs-LIBS spectra of 5 nm thin metal layers with an ablated mass per pulse of 100 femtogram (fg) for Cu and 370 fg for Ag films. The orthogonal double-pulse fs-LIBS enhances the recorded emission line intensities (two to three times) and improves the contrast of chemical images in comparison to single-pulse measurements. The size of ablation craters (diameters as small as 1.5 µm) is not increased by the second laser pulse. The combination of minimally invasive sampling by a tightly focused low-energy fs-pulse and of strong enhancement of plasma emission by an orthogonal high-energy fs-pulse appears promising for future LIBS chemical imaging with high spatial resolution and with high spectrochemical sensitivity.

| S-EPMC9411706 | biostudies-literature

Femtosecond Plasmonic Laser Nanosurgery (fs-PLN) mediated by molecularly targeted gold nanospheres at ultra-low pulse fluences.

Project description:Plasmonic Laser Nanosurgery (PLN) is a novel photomodification technique that exploits the near-field enhancement of femtosecond (fs) laser pulses in the vicinity of gold nanoparticles. While prior studies have shown the advantages of fs-PLN to modify cells, further reduction in the pulse fluence needed to initiate photomodification is crucial to facilitate deep-tissue treatments. This work presents an in-depth study of fs-PLN at ultra-low pulse fluences using 47 nm gold nanoparticles, conjugated to antibodies that target the epithelial growth factor receptor and excited off-resonance using 760 nm, 270 fs laser pulses at 80 MHz repetition rate. We find that fs-PLN can optoporate cellular membranes with pulse fluences as low as 1.3 mJ/cm2, up to two orders of magnitude lower than those used at lower repetition rates. Our results, corroborated by simulations of free-electron generation by particle photoemission and photoionization of the surrounding water, shed light on the off-resonance fs-PLN mechanism. We suggest that photo-chemical pathways likely drive cellular optoporation and cell damage at these off-resonance, low fluence, and high repetition rate fs-laser pulses, with clusters acting as local concentrators of ROS generation. We believe that the low fluence and highly localized ROS-mediated fs-PLN approach will enable targeted therapeutics and cancer treatment.

| S-EPMC7382507 | biostudies-literature

Single Particle Deformation and Analysis of Silica-Coated Gold Nanorods before and after Femtosecond Laser Pulse Excitation.

Project description:We performed single particle deformation experiments on silica-coated gold nanorods under femtosecond (fs) illumination. Changes in the particle shape were analyzed by electron microscopy and associated changes in the plasmon resonance by electron energy loss spectroscopy. Silica-coated rods were found to be more stable compared to uncoated rods but could still be deformed via an intermediate bullet-like shape for silica shell thicknesses of 14 nm. Changes in the size ratio of the rods after fs-illumination resulted in blue-shifting of the longitudinal plasmon resonances. Two-dimensional spatial mapping of the plasmon resonances revealed that the flat side of the bullet-like particles showed a less pronounced longitudinal plasmonic electric field enhancement. These findings were confirmed by finite-difference time-domain (FDTD) simulations. Furthermore, at higher laser fluences size reduction of the particles was found as well as for particles that were not completely deformed yet.

| S-EPMC4973961 | biostudies-literature

Application of femtosecond ultrashort pulse laser to photodynamic therapy mediated by indocyanine green.

Project description:BACKGROUND/AIMS: To evaluate treatment with high peak power pulse energy by femtosecond ultrashort pulse laser (titanium sapphire laser) delivered at an 800 nm wavelength for corneal neovascularisation using photodynamic therapy (PDT) mediated by indocyanine green (ICG). METHODS: Using a gelatin solid as an in vitro corneal model, the safety of laser power was studied to determine if it degenerated gelatin with or without ICG. The authors then induced corneal neovascularisation in rabbit eyes by an intracorneal suturing technique. Fluorescein angiography was used to evaluate occlusion before PDT and 0, 1, 3, and 10 days after PDT. The authors performed light microscopy with haematoxylin eosin staining and transmission electron microscopy to determine thrombosis formation in the neovascular regions. RESULTS: The threshold of peak laser power density ranged from 39 to 53 W/cm(2). Laser irradiation was started 30 seconds after a 10 mg/kg ICG injection, and all irradiated segments were occluded at 0, 1, 3, and 10 days at 3.8 J/cm(2). Light and electron microscopy documented thrombosis formation in the neovascular region. CONCLUSION: Femtosecond pulse laser enhanced by ICG can be used for PDT. Because of effective closure of corneal neovascularisation at a low energy level, the high peak power pulse energy of the femtosecond pulse laser might be more efficacious than continuous wave laser for use with PDT.

| S-EPMC1772167 | biostudies-other

Quasi-steady-state air plasma channel produced by a femtosecond laser pulse sequence.

Project description:A long air plasma channel can be formed by filamentation of intense femtosecond laser pulses. However, the lifetime of the plasma channel produced by a single femtosecond laser pulse is too short (only a few nanoseconds) for many potential applications based on the conductivity of the plasma channel. Therefore, prolonging the lifetime of the plasma channel is one of the key challenges in the research of femtosecond laser filamentation. In this study, a unique femtosecond laser source was developed to produce a high-quality femtosecond laser pulse sequence with an interval of 2.9 ns and a uniformly distributed single-pulse energy. The metre scale quasi-steady-state plasma channel with a 60-80 ns lifetime was formed by such pulse sequences in air. The simulation study for filamentation of dual femtosecond pulses indicated that the plasma channel left by the previous pulse was weakly affected the filamentation of the next pulse in sequence under our experimental conditions.

| S-EPMC4616044 | biostudies-other

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