Effect Of Laser Intensity Research Articles

Parametric analysis of delivered power during laser ablation for prostate cancer.

Abstract Prostate cancer is one of the most recurrent forms of cancer in men, occurring in peripheral zones. Laser ablation is an emerging non-invasive protocol for this disease, offering the possibility to preserve the prostate proper functioning. However, due to shortage of in-vivo experiments, for ethical and practical reasons, it is difficult to properly design the treatment, leading to incomplete tumor destruction and metastasis development, owed to inappropriate exposure time or laser intensity. Consequently, it is of primary importance to develop accurate models to aid and provide guidelines to surgeons, towards a treatment optimization. For these reasons, in this paper an accurate model has been developed and solved through the finite elements commercial software Comsol Multiphysics. A 2D domain, representative of the tumor inside the prostate, has been investigated, using the porous media approach. According to the Local Thermal Non-Equilibrium (LTNE) assumption, the tissue and the blood are treated as two distinct entities having different thermal properties and behavior. The laser source has been described by means of the Beer-Lambert’s law, assuming a Gaussian laser distribution. To find the optimal laser setting to achieve the maximum tumor destruction, the effect of different laser intensity, and bare fiber diameter on temperature field and thermal damage is investigated.

Experimental investigation of toe laser intensity effects on capsule compression in indirect-drive inertial confinement fusion

Abstract In indirect-drive inertial confinement fusion (ICF) research, the meticulous design and optimization of laser parameters are crucial for achieving high-gain ignition. The intensity of the toe laser, used for ablating the hohlraum sealing membrane, is a subtle but equally critical parameter. This study introduces a novel experimental approach using the Velocity Interferometer System for Any Reflector (VISAR) to assess the impact of toe laser intensity on the compression of fusion capsules. By tracking the reflectivity of tracer layers and shock velocities in liquid deuterium, the adverse effects of insufficient toe laser intensity on capsule compression have been unveiled for the first time. From a comparison with hydrodynamic simulations, we show that below a critical threshold of 0.23 × 1014 W cm−2, the adiabat, a measure of the fuel’s compression efficiency, increases markedly with the toe laser intensity decreases, whereas it remains stable within the range of (0.23 ∼ 7) × 1014 W cm−2. Our findings provide critical insights on toe laser parameter design, enhancing our understanding of the role of toe laser intensity in ICF experiments. This research not only refines the parameters for laser operation but also underscores the importance of precision in achieving the desired implosion efficiency, contributing to the development of nuclear fusion as a clean energy source.

Enhanced laser-target energy coupling through counter-propagating lasers: Insights from electron recirculation

In the interaction between lasers of relativistic intensity and targets, a portion of the laser energy is carried by relativistic fast electrons, which usually cannot be deposited inside but escapes from the target. Here, we explored a method to reduce this energy waste and enhance laser-target energy coupling through counter-propagating lasers. Particle-in-cell simulation results show that high-energy fast electrons generated by the laser on one side can be re-accelerated by the laser on the other side through the synergistic effect of the reflected laser and longitudinal electric field after passing through the target, and then reflected back into the target by a potential barrier, forming an electron recirculation. Through this electron recirculation, the energy conversion efficiency of each laser is significantly improved, and the temperature of electrons and ions inside the target is effectively increased by 118 % and 29 %, respectively. We also explored the effects of laser intensity and target density through multiple sets of simulations with controlled variables, and summarized the electron recirculation model in such counter-propagating lasers configuration.

Microfluidic Laser-Induced Nucleation of Iron (II,III) Oxide Nanoparticle-Doped Supersaturated Aqueous KCl Solutions.

A capillary-based microfluidic system designed for nonphotochemical laser-induced nucleation (NPLIN) studies coupled with real-time microscopy was used to study NPLIN of iron (II,III) oxide doped aqueous KCl solutions. Supersaturation was achieved by lowering the solution temperature using thermoelectric cooling, and heating was used for the dissolution of crystals downstream to prevent clogging during the flow. The effect of nanoparticle concentration, supersaturation, laser intensity, and filtration was studied. We report laser-induced nucleation using laser intensities as low as 1 MW/cm2 with nanoparticle number densities of ∼109 particles per mL of solution at KCl supersaturations from 1.06 to 1.08. The number of crystals increased with increasing laser intensity, supersaturation, and nanoparticle concentration. We discuss our results with respect to the colloidal impurity-heating mechanism hypothesis and propose a semiempirical model based on the nanoparticle heating and bubble formation due to the absorption of laser energy.

Photobiomodulation transiently increases the spontaneous firing in the superficial layer of the rat spinal dorsal horn

The therapeutic benefits of photobiomodulation (PBM) in pain management, although well documented, are accompanied by concerns about potential risks, including pain, particularly at higher laser intensities. This study investigated the effects of laser intensity on pain perception using behavioral and electrophysiological evaluations in rats. Our results show that direct laser irradiation of 1000mW/cm2 to the sciatic nerve transiently increases the frequency of spontaneous firing in the superficial layer without affecting the deep layer of the spinal dorsal horn, and this effect reverses to pre-irradiation levels after irradiation. Interestingly, laser irradiation at 1000mW/cm2, which led to an increase in spontaneous firing, did not prompt escape behavior. Furthermore, a significant reduction in the time to initiate escape behavior was observed only at 9500mW/cm2 compared to 15, 510, 1000, and 4300mW/cm2. This suggests that 1000mW/cm2, the laser intensity at which an increase in spontaneous firing was observed, corresponds to a stimulus that did not cause pain. It is expected that a detailed understanding of the risks and mechanisms of PBM from a neurophysiological perspective will lead to safer and more effective use of PBM.

All-fiber light intensity sensor employing a three-core fiber taper integrated by magnetic fluids

All-fiber light intensity sensor employing a three-core fiber taper integrated by magnetic fluids

Simulation on mass removal by recoil pressure, thermal stress, and bubble growth of concrete irradiated by a millisecond Nd: YAG pulsed laser

Simulation on mass removal by recoil pressure, thermal stress, and bubble growth of concrete irradiated by a millisecond Nd: YAG pulsed laser

Transient responses of dielectrics during ultrashort pulsed laser irradiation using a generalized thermoelastic model considering temperature-dependent thermophysical properties

Transient responses of dielectrics during ultrashort pulsed laser irradiation using a generalized thermoelastic model considering temperature-dependent thermophysical properties

Effect of Laser Intensity on an Electron’s Optimal Position and Spatial Radiation Characteristics in a Linearly Polarized Tightly Focused Laser Field

Effect of Laser Intensity on an Electron’s Optimal Position and Spatial Radiation Characteristics in a Linearly Polarized Tightly Focused Laser Field

Design and Validation of a Droplet-based Microfluidic System To Study Non-Photochemical Laser-Induced Nucleation of Potassium Chloride Solutions.

Non-photochemical laser-induced nucleation (NPLIN) has emerged as a promising primary nucleation control technique offering spatiotemporal control over crystallization with potential for polymorph control. So far, NPLIN was mostly investigated in milliliter vials, through laborious manual counting of the crystallized vials by visual inspection. Microfluidics represents an alternative to acquiring automated and statistically reliable data. Thus we designed a droplet-based microfluidic platform capable of identifying the droplets with crystals emerging upon Nd:YAG laser irradiation using the deep learning method. In our experiments, we used supersaturated solutions of KCl in water, and the effect of laser intensity, wavelength (1064, 532, and 355 nm), solution supersaturation (S), solution filtration, and intentional doping with nanoparticles on the nucleation probability is quantified and compared to control cooling crystallization experiments. Ability of dielectric polarization and the nanoparticle heating mechanisms proposed for NPLIN to explain the acquired results is tested. Solutions with lower supersaturation (S = 1.05) exhibit significantly higher NPLIN probabilities than those in the control experiments for all laser wavelengths above a threshold intensity (50 MW/cm2). At higher supersaturation studied (S = 1.10), irradiation was already effective at lower laser intensities (10 MW/cm2). No significant wavelength effect was observed besides irradiation with 355 nm light at higher laser intensities (≥50 MW/cm2). Solution filtration and intentional doping experiments showed that nanoimpurities might play a significant role in explaining NPLIN phenomena.

16Cr3Al-Hf ODS steel: Surface effects of high laser intensity of 1015 W/cm2 in ambiences of air, helium and vacuum

16Cr3Al-Hf ODS steel: Surface effects of high laser intensity of 1015 W/cm2 in ambiences of air, helium and vacuum

Effects of pump laser intensity on the cell temperature working point in a K-Rb-21Ne spin-exchange relaxation-free co-magnetometer.

The cell temperature working point optimization of the spin-exchange relaxation-free (SERF) co-magnetometer is studied theoretically and experimentally in this article. Based on the steady-state solution of the Bloch equations, the steady-state response model of the K-Rb-21Ne SERF co-magnetometer output signal with cell temperature is established in this paper. And combined with the model, a method to find the optimal working point of the cell temperature that incorporates the pump laser intensity is proposed. The scale factor of the co-magnetometer under different pump laser intensities and cell temperatures is obtained experimentally, and the long-term stability of the co-magnetometer at the different cell temperatures with corresponding pump laser intensities is measured. The results show that the bias instability of the co-magnetometer is reduced from 0.0311 deg/h to 0.0169 deg/h by obtaining the optimal working point of the cell temperature, which verifies the validity and accuracy of the theoretical derivation and the proposed method.

Transition metal dichalcogenide coated gold nanoshells for highly effective photothermal therapy.

Transition metal dichalcogenides (TMD) coated gold nanoshells (GNSs), in addition to having low cytotoxicity and a biocompatibility value greater than graphene, exhibit strong light absorption in the near-infrared (NIR) region and high photothermal conversion efficiency. Using a quasi-static approach and bioheat equations, the optical and photothermal properties of GNSs coated with various TMDs are studied for treatment of skin cancer. Our findings show that the intensity of localized surface plasmon resonance (LSPR) peaks and their position in the extinction spectrum of nanoparticles (NPs) can be easily tuned within biological windows by varying the core radius, the gold shell thickness and the number of coating layers of the different TMDs. In order to engineer heat production at designated spatial locations of NPs, near electric field (NEF) enhancement is investigated. Moreover, the effect of laser intensity and the number of TMD layers on the temperature rise and the amount of thermal damage in skin tumor tissue and its surroundings are studied. Our results introduce GNSs with various TMD coatings as superlative nanoagents for photothermal therapy (PTT) applications.

Laser Intensity of Thermo-Responsive Nanoparticles Size Measurement Using Dynamic Light Scattering

Dynamic light scattering (DLS) or photon cross-correlation spectroscopy (PCCS) is a very potent means for analyzing the diffusion behaviour of supramolecules in their solution form. The diffusion coefficient, probed from the scattered light by supramolecules underexposure to incident light, allows the hydrodynamic radii to be calculated. However, the scattering values were recently misled by an unexpected interaction between the incident light and thermo-sensitive nanogels. Hence, in turn, it resulted in a miscalculation of the size of the nanogels by more than 100% of their expected values. The study fulfills a vital knowledge gap by investigating the effects of laser intensity on the size of thermo-sensitive Poly(N-Isopropyl Acrylamide-Vinyl Pyrrolidone-Polyethylene Glycol Diacrylate-(2-(Dimethyl Amino)Ethyl Methacrylate)), Poly(NIPAAM-PVP-PEGDA-DMAEMA) nanogels and subsequent count rates in DLS measurements. The Lower Critical Solution Temperature, LCST phase transition of Poly(NIPAAM-PVP-PEGDA-DMAEMA) nanogel can be observed using the DLS technique. The higher laser intensity was advantageous for measuring at high dilution more vigorously with varying laser intensities. Thus, a sufficient laser intensity should be chosen based on the light scattering characteristics of typical samples.

Effect of blue diode laser intensity on welding of pure copper wire using blue-IR hybrid laser

A welding of a pure copper wire was conducted with a hybrid laser system, which combines a blue laser and an infrared (IR) laser to achieve a highly efficient and spatterless laser welding of pure copper. In the experiment, a blue-IR hybrid laser was irradiated onto a 3 × 3 × 20 mm3 pure copper wire, and the intensity of the blue laser was varied to clarify the effect of the combining of the blue diode laser. While irradiating the laser, the sample was observed by using a high-speed video camera, and the temperature of the processing point was measured by using a thermal camera. After laser irradiation, a molten volume and welding efficiency was evaluated. It was clarified that the welding efficiency of the pure copper wire increased as the intensity of the blue laser increased. At the maximum, the welding efficiency with a 6.31 × 107 W/cm2 IR laser became 1.88 times higher by combining a 9.98 × 105 W/cm2 blue laser. This finding can contribute to a further increase in the welding efficiency of pure copper wires, leading to high production efficiency in the pure copper welding process.

Laser-driven ionization mechanisms of aluminum for single particle aerosol mass spectrometry

Single particle aerosol mass spectrometry (SPAMS), an analytical technique for measuring the size and composition of individual micron-scale particles, is capable of analyzing atmospheric pollutants and bioaerosols much more efficiently and with more detail than conventional methods which require the collection of particles onto filters for analysis in the laboratory. Despite SPAMS’ demonstrated capabilities, the primary mechanisms of ionization are not fully understood, which creates challenges in optimizing and interpreting SPAMS signals. In this paper, we present a well-stirred reactor model for the reactions involved with the laser-induced vaporization and ionization of an individual particle. The SPAMS conditions modeled in this paper include a 248 nm laser which is pulsed for 8 ns to vaporize and ionize each particle in vacuum. The ionization of 1 μm, spherical Al particles was studied by approximating them with a 0-dimensional plasma chemistry model. The primary mechanism of absorption of the 248 nm photons was pressure-broadened direct photoexcitation to Al(y2D). Atoms in this highly excited state then undergo superelastic collisions with electrons, heating the electrons and populating the lower energy excited states. We found that the primary ionization mechanism is electron impact ionization of various excited state Al atoms, especially Al(y2D). Because the gas expands rapidly into vacuum, its temperature decreases rapidly. The rate of three-body recombination (e− + e− + Al+ → Al + e−) increases at low temperature, and most of the electrons and ions produced recombine within several μs of the laser pulse. The importance of the direct photoexcitation indicates that the relative peak heights of different elements in SPAMS mass spectra may be sensitive to the available photoexcitation transitions. The effects of laser intensity, particle diameter, and expansion dynamics are also discussed.

Spectroscopy Diagnostic of Laser Intensity Effect on Zn Plasma Parameters Generated by Nd: YAG Laser

The creation and characterization of laser-generated plasma are affected by laser irradiance, representing significant phenomena in many applications. The present work studied the spectroscopy diagnostic of laser irradiance effect on Zn plasma features created in the air by a Q-switched Nd: YAG laser at the fundamental wavelength (1064nm). The major plasma parameters (electron temperature and electron density) have been measured using the Boltzmann plot and the Stark broadening methods. The value of electrons temperature ranged from 6138–6067 K, and the electron density in the range of 1.4×1018 to 2×1018 cm-3, for laser irradiance range from 2.1 to 4.8×108 (W/cm2). The McWhirter criterion for preserving a local thermodynamic equilibrium (LTE) condition is confirmed in this study. Furthermore, other fundamental plasma parameters, such as Debye length (λD), number of particles in Debye sphere (ND), and plasma frequency (ωp), were measured. We found that all plasma parameters are affected by laser intensity.

High resolution optical investigation of laser intensity and solution temperature effects on thermocavitation

• A non-intrusive optical technique to measure bubble dynamics of thermocavitation. • Effects of laser intensity, temperature, and absorption coefficient on bubble dynamics. • Twin cavitation cases, where a subsequent cavitation bubble appears before the collapse of the previous one. This paper studies cavitation induced by focusing a continuous wave laser in a highly absorbing aqueous copper nitrate solution. The Spatial Transmittance Modulation method was used to detect the cavitation bubbles and verified by high-speed shadowgraphy. The influence of intensity, solution temperature, and absorption coefficient on the cavitation dynamics was investigated by observing the bubble diameters, bubble lifetimes, cavitation times, and cavitation frequencies. The intensity was varied by changing the optical power between 1.2 W and 4.7 W and shifting the laser focal point from 4.5 mm outside to 3.5 mm inside of the cavitating solution by 1 mm increments. Additionally, six solution temperatures between 22 °C to 74 °C were tested, and three concentrations of copper nitrate (10.7, 6.35 and 3.49 g copper nitrate per 10 mL of water) were used to change the solution’s absorption coefficient. The results reveal that on average, larger intensities result in shorter cavitation times, higher frequencies, and higher percentages of small bubbles. Increasing the copper nitrate concentration has a similar effect on the cavitation events. With higher solution temperature, the time to initiate cavitation decreases, and higher percentage of larger bubbles appear due to a decrease of surface tension. However, the solution temperature does not change the cavitation randomness significantly. The findings of this investigation may allow for effective control of thermocavitation dynamics where current laser cavitation applications require managed outcomes.

Collimation and monochromaticity of γ-rays generated by high-energy electron colliding with tightly focused circularly polarized laser with varied intensities

The collision of high-energy electron and laser pulses produces nonlinear inverse Thomson scattering, which can generate γ-rays. We study the effect of laser intensity on the energy angular distribution and spectrum of γ-ray radiation in tightly focused pulses. The γ-rays at non-relativistic intensity have good collimation and monochromaticity, and the radiation energy increases with the laser intensity. The ‘jumping point’ phenomenon of radiation energy variation under relativistic intensity and the ‘black hole’ of energy angular distribution were discovered. As the laser intensity increases, there is a red shift in the radiative harmonic spectrum. And at relativistic intensity, supercontinuum (tunable) γ-rays can be obtained. These findings help us use NITS for optical research.

Magneto-optical trapping of mercury at high phase-space density

We present a realization of a magneto-optical trap of mercury atoms on the intercombination line. We report on trapping of all stable mercury isotopes. We characterize the effect of laser detuning, laser intensity, and gradient field on the trapping performance of our system. The atom number for the most abundant isotope Hg-202 is 50 million atoms. Moreover, we study the difference in cooling processes for bosonic and fermionic isotopes. We observe agreement with the Doppler cooling theory for the bosonic species and show sub-Doppler cooling for the fermionic species. We reach a phase space density of a few parts in 10^-6, which consitutes a promising starting condition for dipole trap loading and evaporative cooling.