Large area uniform femtosecond-laser-induced periodic surface structures fabricated on heated LiNbO3:Fe

The influence of laser fluences and scanning speeds on the morphologies of laser-induced periodic surface structures(LIPSS) on heated LiNbO3:Fe(1000○C) surfaces was investigated under femtosecond(fs) laser scanning irradiation. Laser fluence of 8.5 kJ/m2 and scanning speed of 1 mm/s were found to be optimum process parameters, and large-area fs-LIPSS on LiNbO3:Fe with an area of 8 mm×8 mm were fabricated with these parameters. The wettability of laser-textured LiNbO3:Fe changed to be hydrophilic, and the absorptance was improved substantially in the spectral range of 400-2000 nm. This technique is efficient, and environmentally friendly, which will attract tremendous interest in nano-photoelectron and nano-mechanics.

Study the plasmonic property of gold nanorods highly above damage threshold via single-pulse spectral hole-burning experiments

Intense femtosecond laser irradiation reshapes gold nanorods, resulting in a persistent hole in the optical absorption spectrum of the nanorods at the wavelength of the laser. Single-pulse hole-burning experiments were performed in a mixture of nanorods with a broad absorption around 800 nm with a 35-fs laser with 800 nm wavelength and 6 mJ/pulse. A significant increase in hole burning width at an average fluence of 106 J/m2 has been found, suggesting a tripled damping coefficient of plasmon. This shows that the surface plasmonic effect still occurs at extremely high femtosecond laser fluences just before the nanorods are damaged and the remaining 10% plasmonic enhancement of light is at the fluence of 106 J/m2, which is several orders of magnitude higher than the damage threshold of the gold nanorods. Plasmon–photon interactions may also cause an increase in the damping coefficient.

Study on Ablation Characteristics of Femyosecond Laser Nanoscale Processing for Aluminum Nitride and LeadZirconate Titanate Ceramics

This paper analytically investigates an ultrashort pulsed laser nanoscale processing for aluminum nitride (AIN) and lead zirconate titanate (PZT) ceramics. Processing characteristics of an ultra-short pulsed laser is different from that of long-pulsed laser due to ultrahigh intensity, ultrahigh power, and ultrashort time. The ultrasmall processing for materials can achieved by an ultra-short pulsed laser. This study proposes a model to analyze an ultrashort pulsed laser nanoscale processing for aluminum nitride (AIN) and lead zirconate titanate (PZT) ceramics. The effects of optical penetration absorption and thermal diffusion on temperature are also discussed. The results reveal that the variation of ablation rate with laser fluences predicted by this work agrees with the available measured data for an ultrashort pulsed laser processing for AIN and PZT. For femtosecond lasers, the optical absorption and thermal diffusion, respectively, governs the ablated depth per pulse at the low and high laser fluences. The thermal diffusion length is small relative to the optical penetration depth for femtosecond laser. The optical penetration absorption governs the temperature in the workpiece. On the other hand, for the picosecond laser, the thermal diffusion length is large compared to the optical penetration depth. The thermal diffusion determines the temperature in the workpiece.

Study of Micro/Nano Structuring and Mechanical Properties of KrF Excimer Laser Irradiated Al for Aerospace Industry and Surface Engineering Applications

Micro/nano structuring of KrF Excimer laser-irradiated Aluminum (Al) has been correlated with laser-produced structural and mechanical changes. The effect of non-reactive Argon (Ar) and reactive Oxygen (O2) environments on the surface, structural and mechanical characteristics of nano-second pulsed laser-ablated Aluminum (Al) has been revealed. KrF Excimer laser with pulse duration 20 ns, central wavelength of 248 nm and repetition rate of was utilized for this purpose. Exposure of targets has been carried out for 0.86, 1, 1.13 and 1.27 J.cm−2 laser fluences in non-reactive (Ar) and reactive (O2) ambient environments at a pressure of 100 torr. A variety of characteristics of the irradiated targets like the morphology of the surface, chemical composition, crystallinity and nano hardness were investigated by using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffractometer (XRD), Raman spectroscopy and Nanohardness tester techniques, respectively. The nature (reactive or non-reactive) and pressure of gas played an important role in modification of materials. In this study, a strong correlation is observed between the surface structuring, chemical composition, residual stress variation and the variation in hardness of Al surface after ablation in both ambient (Ar, O2). In the case of reactive environment (O2), the interplay among the deposition of laser energy and species of plasma of ambient gas enhances chemical reactivity, which causes the formation of oxides of aluminum (AlO, Al2O3) with high mechanical strength. That makes it useful in the field of process and aerospace industry as well as in surface engineering.

Optimization laser parameters to simulate solar cell degradation induced by space radiation

Space radiation has a catastrophic impact on solar cells performance, appears as a degradation in their electrical and physical properties, this may cause a satellite failure; to overcome this issue, ground testing is required. In this paper, the pulsed laser was used as an alternative irradiation tool to induce degradation in solar cell performance in order to simulate the space radiation effect on solar cells. Firstly, the solar cells were irradiated with a wavelength of 532 nm at different locations, with the same power to optimize the most effective area to irradiation. Secondly, the solar cells were irradiated to the optimized location with different laser fluences; the results showed a degradation in electrical and physical performance. The amount of degradation is proportional to the laser fluence. Dark current voltage (DIV) curves have been measured before and after laser irradiation. Solar cell degradation rates have been calculated based on the Degradation coefficients (KL, RC) and electrical damage models.

Effects of Different Surfactant Charges on the Formation of Gold Nanoparticles by the LASiS Method

The laser ablation synthesis in solution (LASiS) method has been widely utilized due to its significant prospects in laser microprocessing of nanomaterials. In this study, the LASiS method with the addition of different surfactant charges (cationic CTAB, nonionic TX-100, and anionic SDS) was used to produce Au NPs. An Nd:YAG laser system at 532 nm excitation with some synthetic parameters, including different laser fluences, ablation times, and surfactant concentrations was performed. The obtained Au NPs were characterized by UV-Vis spectroscopy, transmission electron microscopy, and zeta potential analyzer. The Au NPs exhibited the maximum absorption peak at around 520 nm for all samples. The color of Au NPs was changed from red to reddish by increasing the laser fluence. The surfactant charges also played different roles in the Au NPs’ growth during the synthesis process. The average sizes of Au NPs were found to be 8.5 nm, 5.5 nm, and 15.5 nm with the medium containing CTAB, TX-100, and SDS, respectively. Besides, the different surfactant charges induced different performances to protect Au NPs from agglomeration. Overall, the SDS and CTAB surfactants exhibited higher stability of the Au NPs compared to the Au NPs with TX-100 surfactant.

Enhanced Microsphere-Assisted Picosecond Laser Processing for Nanohole Fabrication on Silicon via Thin Gold Coating

The nanohole arrays on the silicon substrate can effectively enhance the light absorption in thin film silicon solar cells. In order to optimize the solar energy absorption, polystyrene microspheres with diameters of 1 μm are used to assist picosecond laser with a wavelength of 1064 nm to fabricate nanohole arrays on silicon substrate. The experimental results show that the morphology and size of the silicon nanoholes strongly depend on the laser fluence. At 1.19–1.59 J/cm2 laser fluences, well-ordered arrays of nanoholes were fabricated on silicon substrate, with diameters domain from 250 to 549 nm and depths ranging from 60 to 99 nm. However, large amounts of sputtered nanoparticles appeared around the silicon nanoholes. To improve the surface morphology of silicon nanoholes, a nanolayered gold coating is applied on silicon surface to assist laser processing. The results show that, for gold-coated silicon substrate, sputtered nanoparticles around the nanoholes are almost invisible and the cross-sectional profiles of the nanoholes are smoother. Moreover, the ablation rate of the nanoholes on the gold-coated silicon substrate have increased compared to that of the nanoholes on the uncoated one. This simple method allows fast fabrication of well-ordered nanoholes on silicon substrate without sputtered nanoparticles and with smooth inner surface.

Preparation and Characterization of Gold Coated Super Paramagnetic Iron Nanoparticle Using Pulsed Laser Ablation in Liquid Method

Fe@Au is a type of nanoparticle that contains magnetic Fe NPs core with a fine layer of Au NPs synthesized using the Pulsed Laser Ablation in Liquid (PLAL) Method. These Fe@Au NPs characterized by Atomic Force Microscope (AFM), Field Emission Scanning Electron Microscopy (FESEM), and UV-Visible Spectrophotometer. The result was obtained at different laser fluences (1.9, 2.2, and 2.5) J/cm2 with fixed pulse duration 5 ns, wavelength 532nm and number of pulse equal 100 pulsed. The obtained mean size of Fe@Au NPs at laser fluence (1.9, 2.2, and 2.5) J/cm2 was (63.65, 32.47 and 31.18) nm respectively. UV-Visible Spectrophotometer carves was showed a redshift toward longer wavelength by increasing particle size. Obtained results exhibited that the laser fluence plays a key role in the size, and dispersity of Fe@Au NPs.

Chemical Analysis of Thermoluminescent Colorless Topaz Crystal Using Laser-Induced Breakdown Spectroscopy

We present results of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) and energy-dispersive X-ray (EDX) analysis of natural colorless topaz crystal of local Pakistani origin. Topaz plasma was produced in the ambient air using a nanosecond laser pulse of width 5 ns and wavelength 532 nm. For the purpose of detection of maximum possible constituent elements within the Topaz sample, the laser fluences were varied, ranging 19.6–37.6 J·cm−2 and optical emission from the plasma was recorded within the spectral range of 250–870 nm. The spectrum obtained has shown the presence of seven elements viz. Al, Si, F, O, H, Na and N. Results shows that the fluorine was detected at laser fluence higher than 35 J·cm−2 and plasma temperature of >1 eV. Al and Si were found as the major compositional elements in topaz crystals. The ratios of concentrations of Al and Si were found as 1.55 and 1.59 estimated by CF-LIBS and EDX, respectively. Furthermore, no impurity was found in the investigated colorless topaz samples.

Laser-impact-induced splashing: an analysis of the splash crown evolution after Nd:YAG ns-pulse laser impact on a liquid tin pool

The splash created by intense laser pulse impact onto a liquid tin layer is studied experimentally using time-delayed stroboscopic shadowgraphy. An 8-ns infrared (1064 nm) laser pulse is focused onto a deep liquid tin pool. Various laser spot sizes (70, 120, and 130 $$\upmu$$ μ m in diameter) and various laser pulse energies (ranging 2.5–30 mJ) are used, resulting in laser fluences of $$\sim$$ ∼ 10–1000 J/cm$$^2$$ 2 inducing pronounced splashing. Specifically, we study the time evolution of the splash crown-width. The crown width expansion velocity is found to be linearly dependent on the laser energy, and independent of the focal spot size. A collapse of all crown width evolution data onto a single master curve confirms that the hydrodynamic evolution of our laser-impact-induced splash is equivalent to droplet-impact-induced splashing. Laser-impact splashing is particularly relevant, e.g. for high-brightness laser-assisted discharge-produced plasma and laser-produced plasma sources of extreme ultraviolet light for nanolithography.