Interaction Of Laser Energy Research Articles

Structural Color Generation on Transparent and Flexible Substrates by Nanosecond Laser Induced Periodic Surface Structures (Adv. Mater. Technol. 10/2023)

Laser Patterning In article number 2201725, Huseung Lee, June Sik Hwang, and co-workers present a unique solution-based process for fabricating laser-induced periodic surface structures (LIPSS) on transparent and flexible substrates using a nanosecond laser. The interaction of laser energy with thin-film-coated transparent substrate results in material reorganization and LIPSS formation. The LIPSS patterns exhibit iridescent structural coloration and are effectively transferred onto polydimethylsiloxane (PDMS).

Study on the Far Field Laser Power Density of the Laser-UAVs with Photovoltaic Panel

The concept of a UAV (unmanned aerial vehicle) with photovoltaic cells powered by a laser beam has been demonstrated as more firm, having higher usable power and more payloads than solar-powered ones, and features wide prospective. This paper analyzes the process of laser energy transmitted in the atmosphere to arrive at the photovoltaic cells. The interaction of laser energy and the atmosphere are analyzed, and the impacts of the diffraction, beam drift caused by turbulence and the aiming precision of the laser launching system on the distribution of laser spot and far field power density. Some bases for laser energy transport are presented.

Interaction of Laser Energy with Bow Shock in Mach 5 Flow

In order to develop a potential way to reduce the stagnation pressure and heat flux of the blunt body in hypersonic flow, single pulsed and high rated laser energy are deposited respectively to control the bow shock in Mach 5 flow. Process of the interaction of 100mJ single pulsed laser energy with bow shock is studied by schlieren experiment in Mach 5 shock tunnel. The results indicate that the schlieren photographs and stagnation pressure at different times fit well with the simulation. Bow shock is distorted by the laser induced blast wave. During a single laser pulse, the average stagnation pressure and temperature are reduced by 6.5% and 3.4%. High rated laser energy is used to sustain the low pressure and heat flux region to increase the control efficiency. With the power of 6.6% of the enthalpy flux, when the distance of deposition point and blunt body is 1.1 times of the diameter of the blunt body, the pressure and heat flux of the stagnation point is reduced to 49% and 75%, respectively. The mechanism of interaction of laser and bow shock is disclosed.

Ultrafast laser melting of Au nanoparticles: atomistic simulations

In spite of the technological importance of laser modification and processing of nanoparticles, the interaction of laser energy with nanoparticles is not well understood. In this work, integrated molecular dynamics (MD) and two-temperature (TTM) computational models have been developed to study ultrafast laser interaction with free Au nanoparticles with sizes 2.44–6.14 nm. At low intensity, when surface premelting and solid–liquid phase transition dominate, a nonhomogeneous surface premelting mechanism was identified. The appearance of a contiguous surface liquid layer (complete surface premelting) is size dependent and is not related to surface premelting history. The effects of temporary superheating and stable supercooling of nanoparticles were found and examined.

Experimental and theoretical/numerical investigations of thin films bonding strength

A laser spallation facility has been developed to measure the strength of planar interfaces between a substrate and a thin coating. This quantity is a central requirement in contemporary thin film and protective coatings technology and its successful measurement should improve the scientific/technological potential for the design of advanced composites, protective coatings of composites that operate in hostile environments, and in joining of dissimilar materials. The technique involves impinging a laser pulse of ultra short duration on the rear surface of the substrate, which is coated by a thin layer of energy absorbing metal such as Sn and Pb. The explosive evaporation of the metallic layer, confined between a fused quartz crystal and the substrate, induces a compressive shock wave, which propagates through the substrate toward the material interface. Upon reflection from the free surface of the coating, the pressure pulse is converted into a tensile wave which, under certain conditions, can lead to spallation at the interface. It is shown by mathematical simulation that atomic bond rupture is the mechanism of separation in this experiment. Since the interaction of laser energy with matter is a complicated, highly non-linear process, our investigations, at first, were based on measurement of the pressure pulse generated by the threshold flux level that leads to spallation, by using a micro-electronics device with a piezo-electric crystal, and on computation of the tensile stress experienced at the material interface, by numerical simulation of the induced stress wave propagation. Several substrate/coating (ceramic/ceramic and ceramic/metal) systems have been investigated such as, 1–15 μm SiC by CVD, 1–4 μm TiC and TiN by PVD coatings on sapphire substrates, as well as 1–2 μm Au, Sn and Ag coatings by sputtering on sapphire, fused quartz and glass substrates. For identically prepared specimens, the measured threshold energy levels are reproducible, thus leading to reproducible bond strength values, while the spall size, as expected, is dependent on the laser pulse energy level. Finally, the bond strength values obtained are in very good agreement with similar data derived by direct experimental techniques based on Laser-Doppler-Interferometry.