Absorption Of Laser Light Research Articles

Three-dimensional integrated stretchable electronics

A method of fabricating a stretchable and flexible electronic device includes forming each of the functional layers is by: (i) forming on an elastomer substrate a conductive interconnect pattern having islands interconnected by bridges; (ii) applying a conductive paste to the islands; (iii) positioning at least one functional electronic component on each island; and (iv) applying heat to cause the conductive paste to reflow. An elastomer encapsulant is formed over the functional electronic components and the conductive interconnect pattern on each of the functional layers. The elastomer encapsulant has a Young's modulus equal to or less than that of the substrate. The encapsulant includes a pigment to increase absorption of laser light. At least one via is laser ablated, which provides electrical connection to any two functional layers. The via is filled with solder paste to create a bond and electrical connection between the functional layers.

Ultrathin Self-Assembled Diphenylalanine Nanosheets through a Gold-Stabilized Strategy for High-Efficiency Adsorption/Desorption/Ionization.

Herein, the ultrathin and robust diphenylalanine (FF) self-assembled nanosheets were fabricated by a gold-stabilized strategy for the first time, using a facile electrospray method followed by a thermal treatment process. The key for the gold-stabilized mechanism was explored, demonstrating that the synergy of the stable binding and steric effect between gold nanoparticles (AuNPs) and the exposed amino groups of FF nanosheets, led to strong thermal stability and solvent resistance of the composites. Contributing to the features of remarkable accessible surfaces and strong laser light absorption ability of this FF/Au nanosheets, two robust functional devices, that is, solid-phase microextraction (SPME) fiber and surface-assisted laser desorption/ionization (SALDI) platforms, were in situ prepared for in vitro and in vivo biological analysis. The findings indicated that the fabricated platforms possessed two advantages: (1) rapid absorption/desorption speed (within 5 min) and (2) remarkable enhancement of ionization efficiency with 2 orders of magnitude. As a result, the extraction efficiency of the SPME fiber and the quantitation ability of SALDI platform were significantly improved. This study not only demonstrated that FF/Au composites could be prepared through an electrospray method followed with thermal-treatment to serve as promising adsorption/desorption/ionization materials for specific applications but also provided useful strategy to advance the ideas for future combination of SPME with LDI technique.

Dynamical resonance shift and unification of resonances in short-pulse laser-cluster interaction

Pronounced maximum absorption of laser light irradiating a rare-gas or metal cluster is widely expected during the linear resonance (LR) when Mie-plasma wavelength $\lambdaM$ of electrons equals the laser wavelength $\lambda$. On the contrary, by performing molecular dynamics (MD) simulations of an argon cluster irradiated by short 5-fs (fwhm) laser pulses it is revealed that, for a given laser pulse energy and a cluster, at each peak intensity there exists a $\lambda$ -- shifted from the expected $\lambdaM$ -- that corresponds to a {\em unified dynamical} LR at which evolution of the cluster happens through very effective unification of possible resonances in various stages, including (i) the LR in the initial time of plasma creation, (ii) the LR in the Coulomb expanding phase in the later time and (iii) anharmonic resonance in the marginally over-dense regime for a relatively longer pulse duration, leading to maximum laser absorption accompanied by maximum removal of electrons from cluster and also maximum allowed average charge states for the argon cluster. Increasing the laser intensity, the absorption maxima is found to shift to a higher wavelength in the band of $\lambda\approx (1-1.5)\lambdaM$ than permanently staying at the expected $\lambdaM$. A naive rigid sphere model also corroborates the wavelength shift of the absorption peak as found in MD and un-equivocally proves that maximum laser absorption in a cluster happens at a shifted $\lambda$ in the marginally over-dense regime of $\lambda\approx (1-1.5)\lambdaM$ in stead of $\lambdaM$ of LR. Present study may find importance for guiding an optimal condition laser-cluster interaction experiment in the short pulse regime.

Vibrations of micron-sized fluid membranes induced via pulsed laser excitation

We study the acoustic vibrations of three different micron-sized square fluid membranes induced by means of a nanosecond pulsed laser. Several vibration modes in the kHz range are excited when the metallic frame, on which the fluid membrane is suspended, undergoes rapid thermal expansion after absorption of the pulsed laser light. The vibration frequencies detected are compared with a model based on bending vibrations of the fluid film similar to those in a solid membrane. Finite element method based simulations are employed to calculate the membrane deformation for different excitation cases of light absorption, as well as the highest excited modes. In addition we explore the effect on the film vibrations due to the inclusion of carbon nanofibers in the fluid membrane. The carbon nanofibers affect the surface tension in a way that couples bending modes to Marangoni waves in the membrane.

Albumin solder covalently bound to a polymer membrane: New approach to improve binding strength in laser tissue soldering in-vitro.

Laser tissue soldering (LTS) based on indocyanine green (ICG)-mediated heat-denaturation of proteins might be a promising alternative technique for micro-suturing, but up to now the problem of too weak shear strength of the solder welds in comparison to sutures is not solved. Earlier reports gave promising results showing that solder supported by carrier materials can enhance the cohesive strength of the liquid solder. In these studies, the solder was applied to the carriers by dip coating. Higher reliability of the connection between the solder and the carrier material is expected when the solder is bound covalently to the carrier material. In the present study a poly(ether imide) (PEI) membrane served as carrier material and ICG-supplemented albumin as solder substrate. The latter was covalently coupled to the carrier membrane under physiological conditions to prevent structural protein changes. As laser source a diode continuous-wave laser emitting at 808 nm with intensities between 250 mW and 1500 mW was utilized. The albumin functionalized carrier membrane was placed onto the tunica media of explanted pig thoracic aortae forming an overlapping area of approximately 0.5×0.5 cm2. All tests were performed in a dry state to prevent laser light absorption by water. Infrared spectroscopy, spectro-photometrical determination of the secondary and primary amine groups after acid orange II staining, contact angle measurements, and atomic force microscopy proved the successful functionalization of the PEI membrane with albumin. A laser power of 450 mW LTS could generate a membrane-blood vessel connection which was characterized by a shear strength of 0.08±0.002 MPa, corresponding to 15% of the tensile strength of the native blood vessel. Theoretically, an overlapping zone of 4.1 mm around the entire circumference of the blood vessel could have provided shear strength of the PEI membrane-blood vessel compound identical to the tensile strength of the native blood vessel. These in-vitro results confirmed the beneficial effects of solder reinforcement by carrier membranes, and suggest LTS with covalently bound solders on PEI substrates for further studies in animal models.

Classical plasma dynamics of Mie-oscillations in atomic clusters

Mie plasmons are of basic importance for the absorption of laser light by atomic clusters. In this work we first review the classical Rayleigh-theory of a dielectric sphere in an external electric field and Thomson’s plum-pudding model applied to atomic clusters. Both approaches allow for elementary discussions of Mie oscillations, however, they also indicate deficiencies in describing the damping mechanisms by electrons crossing the cluster surface. Nonlinear oscillator models have been widely studied to gain an understanding of damping and absorption by outer ionization of the cluster. In the present work, we attempt to address the issue of plasmon relaxation in atomic clusters in more detail based on classical particle simulations. In particular, we wish to study the role of thermal motion on plasmon relaxation, thereby extending nonlinear models of collective single-electron motion. Our simulations are particularly adopted to the regime of classical kinetics in weakly coupled plasmas and to cluster sizes extending the Debye-screening length. It will be illustrated how surface scattering leads to the relaxation of Mie oscillations in the presence of thermal motion and of electron spill-out at the cluster surface. This work is intended to give, from a classical perspective, further insight into recent work on plasmon relaxation in quantum plasmas [1].

Laser-supported hydrothermal wave in low-dense porous substance

AbstractThe generalized theory of terawatt laser pulse interaction with a low-dense porous substance of light chemical elements including laser light absorption and energy transfer in a wide region of parameter variation is developed on the base of the model of laser-supported hydrothermal wave in a partially homogenized plasma. Laser light absorption, hydrodynamic motion, and electron thermal conductivity are implemented in the hydrodynamic code, according to the degree of laser-driven homogenization of the laser-produced plasma. The results of numerical simulations obtained by using the hydrodynamic code are presented. The features of laser-supported hydrothermal wave in both possible cases of a porous substance with a density smaller and larger than critical plasma density are discussed along with the comparison with the experiments. The results are addressed to the development of design of laser thermonuclear target as well as and powerful neutron and X-ray sources.

The Laser ablation of a metal foam: The role of electron–phonon coupling and electronic heat diffusivity

The incidence of energetic laser pulses on a metal foam may lead to foam ablation. The processes occurring in the foam may differ strongly from those in a bulk metal: The absorption of laser light, energy transfer to the atomic system, heat conduction, and finally, the atomistic processes—such as melting or evaporation—may be different. In addition, novel phenomena take place, such as a reorganization of the ligament network in the foam. We study all these processes in an Au foam of average porosity 79% and an average ligament diameter of 2.5 nm, using molecular dynamics simulation. The coupling of the electronic system to the atomic system is modeled by using the electron–phonon coupling, g, and the electronic heat diffusivity, κe, as model parameters, since their actual values for foams are unknown. We show that the foam coarsens under laser irradiation. While κe governs the homogeneity of the processes, g mainly determines their time scale. The final porosity reached is independent of the value of g.

Laser Light Absorption Layer for Dry Laser Peeing of Thin Films

Laser Light Absorption Layer for Dry Laser Peeing of Thin Films

Effect of laser absorption on picosecond laser ablation of Cr12MoV mold steel, 9Cr18 stainless steel and H13A cemented carbide

Due to excellent properties, Cr12MoV mold steel, 9Cr18 stainless steel and H13A cemented carbide are widely used in industry. In this paper, the effect of absorption of laser light on ablation efficiency and roughness have been studied using a picosecond pulse Nd:YVO4 laser. The experimental results reveal that laser wavelength, original surface roughness and chemical composition play an important role in controlling ablation efficiency and roughness. Firstly, higher ablation efficiency with lower surface roughness is achieved on the ablation of 9Cr18 at 532, comparing with 1064 nm. Secondly, the ablation efficiency increases while the Ra of the ablated region decreases with the decrease of original surface roughness on ablation of Cr12MoV mold steel at 532 nm. Thirdly, the ablation efficiency of H13A cemented carbide is much higher than 9Cr18 stainless steel and Cr12MoV mold steel at 1064 nm. Scanning electron microscopy images reveals the formation of pores on the surface of 9Cr18 stainless steel and Cr12MoV mold steel at 532 nm while no pores are formed at 1064 nm. As to H13A cemented carbide, worm-like structure is formed at 1064 nm. The synergetic effects of the heat accumulation, plasma shielding and ablation threshold on laser ablation efficiency and machining quality were analyzed and discussed systematically in this paper.

Visible light laser-induced graphene from phenolic resin: A new approach for directly writing graphene-based electrochemical devices on various substrates

The cost-effective construction of self-designed conductive graphene patterns on desired substrates is crucial to the fabrication of graphene-based electrochemical devices. Here, we report a new approach for the scalable construction of laser-induced graphene (LIG) patterns on diverse substrates by using phenolic resin (PR) as the precursor. The PR-based LIG, which was produced with smart and inexpensive 405 nm semiconductor lasers under ambient conditions, possesses several interesting properties, e.g., 3D porous structures, low resistance (∼44 Ω/sq), good mechanical property and a wide range of applicable substrates, e.g., polymer films, glass slides, metal foils, ceramic plates and plant leaves. The efficient absorption of laser light by PR coatings themselves or dopants such as metal salts and organic dyes is demonstrated critical to the formation of PR-based LIG by visible light lasers. Based on this technique, self-designed and highly conductive graphene arrays can be easily constructed on various substrates to fabricate all-carbon supercapacitors and electrochemical glucose biosensors. The unique properties of PR materials, including easy synthesis, tunable structure and composition, excellent film-formation ability and extremely low cost, thus foresee the promising applications of PR-based LIG in electrochemical fields.

Improve the material absorption of light and enhance the laser tube bending process utilizing laser softening heat treatment

Laser forming is a flexible control process that has a wide spectrum of applications; particularly, laser tube bending. It offers the perfect solution for many industrial fields, such as aerospace, engines, heat exchangers, and air conditioners. A high power pulsed Nd-YAG laser with a maximum average power of 300 W emitting at 1064 nm and fiber-coupled is used to irradiate stainless steel 304 (SS304) tubes of 12.7 mm diameter, 0.6 mm thickness and 70 mm length. Moreover, a motorized rotation stage with a computer controller is employed to hold and rotate the tube. In this paper, an experimental investigation is carried out to improve the laser tube bending process by enhancing the absorption coefficient of the material and the mechanical formability using laser softening heat treatment. The material surface is coated with an oxidization layer; hence, the material absorption of laser light is increased and the temperature rapidly rises. The processing speed is enhanced and the output bending angle is increased to 1.9° with an increment of 70% after the laser softening heat treatment.

Numerical modelling of the cluster targets for their optimization in femtosecond-laser-cluster-driven experiments

AbstractThe interaction of femtosecond ultra-intense laser pulses with clusters increases absorption of the incident laser light compared with the interaction with solid targets and leads to enhanced generation of different quantum beams with unique parameters. Future investigations of such interaction urgently need detailed modeling and optimization of cluster parameters, for instance, in order to obtain the clusters with desired size, or some specific spatial configuration of the target etc. A numerical model of gas-cluster targets production by the nozzle flows of gases and binary mixtures is presented. Some previous results of the model utilization are summarized, and some new results are given. Techniques of experimental verification of the numerical results are discussed.

OPTIMIZATION OF CO2 LASER PARAMETERS FOR WOOD CUTTIOPTIMIZATION OF CO2 LASER PARAMETERS FOR WOOD CUTTING

By taking advantage of the best characteristics of wood, modern production methods can offer hard wearing and ecological solutions in industrial construction, house building, machinery construction, furniture manufacturing, transport and many other industries. Laser cutting process is an alternative choice to prepare the final shape of wood parts. Materials like wood have good laser light absorption of wavelength 10600 nm. In this paper a CO2 laser system with a maximum continuous-wave output power of 150 W is described and used in studying laser cutting process of wood materials. Cut depth is evaluated with variation of values of laser power and cutting speed. Additionally, optimal values of parameters for laser cutting of different wood plate thicknesses are determined and graphs are created showing the results.

Photoacoustic detection of circulating melanoma cells as a predictor of metastasis in stage III patients.

e21053 Background: Circulating tumor cells have been correlated with disease state and distant metastatic spread in cancer patients. We postulated that enumerating circulating melanoma cells (CMCs) may predict the onset of distant metastasis in Stage III patients. We detected CMCs using our photoacoustic flow cytometer, in which we irradiated enriched blood samples with nanosecond pulsed laser light. While there is no effect on non-optically active leukocytes, absorption of laser light by pigmented melanoma cells resulted in robust ultrasonic waves that indicated CMCs in the sample. Methods: We tested 32 archived samples from 9 Stage III melanoma patients using our photoacoustic flow cytometer. Each patient had between 2 and 6 serial blood samples. We used a pulsed Nd:YAG laser to irradiate mononuclear cells in suspension and under flow. The number of CMCs detected after testing was recorded, indicating the time sequence of circulating tumor cell activity. Results: The numbers of CTCs for each sample is shown in the table below. The ultimate disease state, whether the patient became metastatic or not, was blinded to the investigators who performed the photoacoustic tests. One sample for patient 3 indicated 63 CMCs, though this test was known to be contaminated and had an unknown number of false detections. Conclusions: We found that patients who had a series of more than 4 CMCs were more likely to become metastatic than those patients who tested for 4 CMCs for fewer, indicating that a sequence of CMC detections in serial blood draws provides a potentially strong predictor of metastasis in Stage III melanoma patients warranting further investigation at this and lower stages of melanoma. We are developing a more rigorous model based on time series analysis of CMCs for prediction of metastasis. [Table: see text]

Melt ejection from copper target in air in the presence of magnetic field using nanosecond pulsed laser ablation

The authors report on the study of the crater generated using a nanosecond laser on a copper target in air in the presence of uniform and nonuniform magnetic fields. The analysis of particles deposited inside and around the crater revealed that the generation of large particles (≥0.68 μm) is due to the melt ejection and instability in the liquid layer. The presence of a nonuniform magnetic field causes an additional drift to molten liquid which in turn increases the Kelvin–Helmholtz instability. The percentage of large particles increased due to the enhancement in the Kelvin–Helmholtz instability and mass ejection. The intensity of copper atomic transitions was enhanced in the presence of a uniform magnetic field compared to a nonuniform magnetic field. This is more likely due to an increase in melt ejected mass in the plasma in the presence of a nonuniform magnetic field which may scatter or absorb laser light which in turn decreases laser–matter interaction. The energy-dispersive x-ray spectroscopy and Raman spectroscopy showed the deposited particles are Cu2O. In the presence of a nonuniform magnetic field, the intensity of Raman Cu2O was enhanced, which is attributed to an increase in the number of Cu2O particles.

Biocompatible astaxanthin as a novel marine-oriented agent for dual chemo-photothermal therapy.

The photothermal effect of a marine-oriented xanthophyll carotenoid, astaxanthin (AXT), was characterized based on its potential absorption of visible laser light and conversion of optical light energy into heat for thermal treatment. As an antioxidant and anticancer agent, AXT extracted from marine material can be utilized for photothermal therapy due to its strong light absorption. The current study investigated the feasibility of the marine-based material AXT to increase the therapeutic efficacy of chemo-photothermal therapy (PTT) by assessing photothermal sessions in both cells and tumor tissues. A quasi-cw Q-switched 80 W 532 nm laser system was utilized to induce thermal necrosis in in vitro and in vivo models. An in vitro cytotoxicity study of AXT was implemented using squamous cell carcinoma (VX2) and macrophage (246.7) cell lines. In vivo PTT experiments were performed on 17 rabbits bearing VX2 tumors on their eyes that were treated with or without intratumoral injection of AXT at a dose of 100 μl (300 μg/ml) followed by laser irradiation at a low irradiance of 0.11 W/cm2. Fluorescence microscopy images revealed cellular death via apoptosis and necrosis owing to the dual chemo-photothermal effects induced by AXT. In vivo experimental results demonstrated that the AXT-assisted irradiation entailed a temperature increase by 30.4°C after tumor treatment for 4 min. The relative variations in tumor volume confirmed that the tumors treated with both AXT and laser irradiation completely disappeared 14 days after treatment, but the tumors treated under other conditions gradually grew. Due to selective light absorption, AXT-assisted laser treatment could be an effective thermal therapy for various drug-resistant cancers.

Ambient Characterization of Synthetic Fibers by Laser Ablation Electrospray Ionization Mass Spectrometry.

Direct analysis of synthetic fibers under ambient conditions is highly desired to identify the polymer, the finishes applied and irregularities that may compromise its performance and value. In this paper, laser ablation electrospray ionization ion mobility time-of-flight mass spectrometry (LAESI-IMS-TOF-MS) was used for the analysis of synthetic polymers and fibers. The key to this analysis was the absorption of laser light by aliphatic and aromatic nitrogen functionalities in the polymers. Analysis of polyamide (PA) 6, 46, 66, and 12 pellets and PA 6, 66, polyaramid and M5 fibers yielded characteristic fragment ions without any sample pretreatment, enabling their unambiguous identification. Synthetic fibers are, in addition, commonly covered with a surface layer for improved adhesion and processing. The same setup, but operated in a transient infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) mode, allowed the detailed characterization of the fiber finish layer and the underlying polymer. Differences in finish layer distribution may cause variations in local properties of synthetic fibers. Here we also show the feasibility of mass spectrometry imaging (MSI) of the distribution of a finish layer on the synthetic fiber and the successful detection of local surface defects.

Optical Characteristics of Metallic Nanoparticles During Melting by Laser Radiation

The cross sections and efficiencies of absorption, scattering, and attenuation of laser light with λ = 532 nm and in the 475–625 nm range for two-layered spherical gold nanoparticles with radii r00 = 10, 25, 50, 75, and 100 nm and radii of the solid and liquid cores ranging from 0–r00 are calculated theoretically and studied. It is found that the variation in the optical parameters of a nanoparticle with changes in the aggregate state of the material (melting) has a decisive influence on the heating dynamics of the nanoparticle above the melting point and on the subsequent thermal processes.

Quantum-Plasma Model of Atomic Cluster Excitations

The laser-light absorption of a thin foil is studied in the framework of the self-consistent time-dependent Hartree theory. It is found that asympotically for large numbers of electron states, a single-state Vlasov model is sufficient to describe the main features of the energy absorption to a very good approximation. Since the single-state model is numerically feasible, this allows one to calculate the energy absorption over a wide range of laser parameters. Studying the size-dependence of the absorption mechanism, quantum-mechanical modifications of the well-known classical Brunel theory can be observed for thin layers.