Parametric Study of the Ablation Characteristics of Absorbing Dielectrics by Short Pulse Laser

2000 ◽  
Author(s):  
Samuel George ◽  
Kunal Mitra
Keyword(s):  
Parametric Study ◽  
Short Pulse ◽  
Mathematical Formulation ◽  
Ablation Depth ◽  
Heat Diffusion ◽  
Photon Absorption ◽  
Rate Equations ◽  
Laser Source ◽  
Heat Diffusion Equation ◽  
Short Pulse Laser

Abstract This paper investigates the effect of ablation of absorbing dielectrics by two successive ultra short pulses from an excimer laser source. The numerical model is based on two photon absorption followed by thermal degradation and diffusion. Unlike most previous studies the present formulation considers the transient nature of laser propagation within the medium. Heating of the material is dependent on light absorption by chromophores while ablation occurs through sublimation of the material from the surface. The mathematical formulation takes into consideration the saturation effects within the framework of a three level system of the electronic structure of chromophores. This involves solving a set of coupled rate equations, heat diffusion equation, and the transient radiative transport equation, using Fromm’s scheme. Results for the temperature distribution and ablation depth are obtained for different laser parameters and material properties. Parametric study of the delay time between two successive pulses, laser pulse width, laser fluence, activation energy, and the relaxation time is only performed in this paper for the purpose of brevity. The results obtained by the consideration of the transient radiative transfer equation are compared with the steady state formulation and significant differences are observed in the temperature profiles and the ablation depth.

Error analysis and calibration of a spectroscopic Mueller matrix polarimeter using a short-pulse laser source

2002 ◽  
Vol 13 (10) ◽  
pp. 1563-1573 ◽  
Author(s):  
B Boulbry ◽  
B Le Jeune ◽  
B Bousquet ◽  
F Pellen ◽  
J Cariou ◽  
...  
Keyword(s):  
Error Analysis ◽  
Pulse Laser ◽  
Short Pulse ◽  
Mueller Matrix ◽  
Laser Source ◽  
Short Pulse Laser

Ablation Characteristic Analysis of Short Pulse Laser Processing Composite Materials

2011 ◽  
Vol 189-193 ◽  
pp. 3759-3763 ◽  
Author(s):  
Yun Ping Pan ◽  
Wen Juan Yang ◽  
Yi Min Mo
Keyword(s):  
Femtosecond Laser ◽  
Short Pulse ◽  
Picosecond Laser ◽  
Photon Absorption ◽  
Characteristic Analysis ◽  
Reinforced Plastics ◽  
Short Pulse Laser ◽  
Processing Abilities ◽  
Short Pulse Lasers ◽  
Fiber Reinforced Plastics

Short pulse lasers, including picosecond laser and femtosecond laser are involved to investigate the ablation characteristics of processing carbon fiber reinforced plastics (CFRPs). The ablation threshold of the femtosecond laser, 0.453 J/cm2, is twice higher than that of the picosecond laser 0.867 J/cm2, since the former generates an intense and shorter pulse and the atoms excitation and multi-photon absorption may occur as short as 10 ps or less. The ablation test also describes the processing qualities, where the femtosecond laser has processing abilities without visible thermal defects or charring over the picosecond laser.

Analysis of Microscale Heat Transfer and Ultrafast Thermoelasticity in a Multi-Layered Metal Film

2009 ◽  
Author(s):  
Tsung-Wen Tsai ◽  
Yung-Ming Lee ◽  
Yang-Hsu Liao
Keyword(s):  
Heat Transfer ◽  
Short Pulse ◽  
Early Stage ◽  
Thermal Response ◽  
Laser Source ◽  
Heating Process ◽  
Hot Electron ◽  
Contact Conductance ◽  
Short Pulse Laser ◽  
Ultra Short Pulse

The micro-scale heat transfer and ultrafast thermoelasticity of a gold-chromium film subjected to ultra-short pulse laser heating is investigated. To predicate the thermal response accurately, the ballistic motion and hot electron diffusion are adopted in the laser source term. The ultrafast thermoelasticity (UTE) model with the modified laser heat source is applied to solve ultrafast thermoelastic behaviors inside a two-layered thin-film and the effect of the contact conductance on the thermo-elastic fields is included in the analysis. It is found that the excessive concentration stress appears at the interface due to the contact conductance effect. Therefore, the mechanical failure or damage may occur at the interface during the very early stage of the heating process even though the thermal resistance is extremely small (as small as 10−7 m2K/W).

scholarly journals A Numerical Study of Diffusion of Nanoparticles in a Viscous Medium During Solidification

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Kazi M. Rahman ◽  
M. Ruhul Amin ◽  
Ahsan Mian
Keyword(s):  
Fluid Flow ◽  
Marangoni Number ◽  
Numerical Study ◽  
Control Volume ◽  
Mathematical Formulation ◽  
Heat Diffusion ◽  
Solidification Time ◽  
Original Position ◽  
Heat Diffusion Equation ◽  
Metal Matrix Nanocomposites

Abstract In the field of additive manufacturing process, laser cladding is widely considered due to its cost effectiveness, small localized heat generation, and full fusion to metals. Introducing nanoparticles with cladding metals produces metal matrix nanocomposites, which in turn improves the material characteristics of the clad layer. The governing equations that control the fluid flow are standard incompressible Navier–Stokes and heat diffusion equation, whereas the Euler–Lagrange approach has been considered for particle tracking. The mathematical formulation for solidification is adopted based on enthalpy porosity method. Liquid titanium has been considered as the initial condition where particle distribution has been assumed uniform throughout the geometry. A numerical model implemented in a commercial software based on control volume method has been developed, which allows to simulate the fluid flow during solidification as well as tracking nanoparticles during this process. A detailed parametric study has been conducted by changing the Marangoni number, convection heat transfer coefficient, constant temperature below the melting point of titanium, and insulated boundary conditions to analyze the behavior of the nanoparticle movement. The influence of increase in Marangoni number results in a higher concentration of nanoparticles in some portions of the geometry and lack of nanoparticles in rest of the geometry. The high concentration of nanoparticles decreases with a decrease in Marangoni number. Furthermore, an increase in the rate of solidification time limits the nanoparticle movement from its original position which results in different distribution patterns with respect to the solidification time.

Mathematical Models for Analyzing Tissue Ablation Using Short Pulse Lasers

2009 ◽  
Author(s):  
Ogugua Onyejekwe ◽  
Amir Yousef Sajjadi ◽  
Ugur Abdulla ◽  
Kunal Mitra ◽  
Michael Grace
Keyword(s):  
Temperature Distribution ◽  
Laser Beam ◽  
Heat Equation ◽  
Surface Temperature ◽  
Mathematical Models ◽  
Short Pulse ◽  
Ablation Depth ◽  
Tissue Ablation ◽  
Surface Temperature Distribution ◽  
Short Pulse Laser

Mathematical modeling of biological tissue ablation performed using a short pulse laser and the corresponding experimental analysis is of fundamental importance to the understanding and predicting the temperature distribution and heat affected zone for advancing surgical application of lasers. The objective of this paper is to use mathematical models to predict the thermal ablated zones during irradiation of freshly excised mouse skin tissue samples by a novel approach using a focused laser beam from a short pulse laser source. Suggested mathematical model is Stefan kind free boundary problem for the heat equation in unknown region. Temperature of the skin satisfies the classical heat equation subjected to Neumann boundary condition on the known boundary, while along the time-dependent unknown boundary, which characterizes the ablation depth, two conditions are met: (1) temperature is equal to the ablation temperature and (2) classical Stefan condition is satisfied. The latter expresses the conservation of energy at the ablation moment. A method of integral equations is used to reduce the Stefan problem to a system of two Volterra kind integral equations for temperature and ablation depth. MATLAB is used subsequently for the numerical solution. Experiments are performed using two lasers—a diode laser having a wavelength of 1552 nm and pulsewidth of 1.3 ps. The surface temperature distribution is measured using an imaging camera. After irradiation, histological studies of laser irradiated tissues are performed using frozen sectioning technique to determine the extent of thermal damage caused by the laser beam. The ablation depth and width is calculated based on the interpolated polygon technique using image processing software. The surface temperature distribution and the ablation depth obtained from the mathematical models are compared with the experimental measurements and are in very good agreement. A parametric study of various laser parameters such as time-average power, pulse repetition rate, pulse energy, and irradiation time is performed to determine the necessary ablation threshold parameters.

Experimental and Numerical Analysis of Thermal Ablation in Biological Tissues Using Short Pulse Lasers

2010 ◽  
Author(s):  
Amir Sajjadi ◽  
Ogugua Onyejekwe ◽  
Kunal Mitra ◽  
Michael S. Grace
Keyword(s):  
Pulse Laser ◽  
Continuous Wave ◽  
Short Pulse ◽  
Skin Surface ◽  
Biological Tissues ◽  
Tumor Ablation ◽  
Laser Source ◽  
Striated Muscles ◽  
Short Pulse Laser ◽  
Ultra Short Pulse

For the past few years various photothermal methods such as Laser-induced Hyperthermia [1] and Laser Interstitial Thermal Therapy [2] has been developed for tumor ablation. In all of these existing techniques, either continuous wave (CW) or long pulse laser sources have been used, which often produces heat affected zones that are larger than the boundaries of the tumor, which leads to collateral damage of surrounding healthy tissue. Moreover for these applications, either collimated or diffused laser beams are used, resulting in much of the energy being absorbed by tissues at the skin surface and very little remaining energy penetrating the skin. Such drawbacks can be eliminated if a beam from a short pulse laser source is focused directly at the targeted subsurface location. Tight focusing ensures that sufficient intensity to drive nonlinear optical absorption can be achieved with low pulse energy. This technique has been effectively used in applications such as non-ablative dermal remodeling [3] and treatment of striated muscles [4]. However, the use of focused beam from an ultra-short pulse laser source has never been applied to tumor ablation and is investigated in this paper.

scholarly journals Three-Photon Absorption in Zno Film Using Ultra Short Pulse Laser

2012 ◽  
Vol 03 (08) ◽  
pp. 856-864 ◽  
Author(s):  
Raied K. Jamal ◽  
Mohammed T. Hussein ◽  
Abdulla M. Suhail
Keyword(s):  
Pulse Laser ◽  
Short Pulse ◽  
Photon Absorption ◽  
Zno Film ◽  
Short Pulse Laser ◽  
Ultra Short Pulse ◽  
Ultra Short Pulse Laser

Experimental and Numerical Analysis of Temperature Distribution in Layered Tissue Media Due to Short Pulse Laser Irradiation

Volume 4 ◽  
2004 ◽  
Author(s):  
Ashish Trivedi ◽  
Soumyadipta Basu ◽  
Kunal Mitra ◽  
Sunil Kumar
Keyword(s):  
Pulse Laser ◽  
Lower Layer ◽  
Short Pulse ◽  
Skin Layer ◽  
Laser Source ◽  
Fatty Tissue ◽  
Measured Temperature ◽  
Conduction Model ◽  
Pulse Laser Irradiation ◽  
Short Pulse Laser

Use of short pulse laser for minimally invasive therapeutic treatment has become an indispensable tool in the technological arsenal of modern medicine and biomedical engineering. The objective of this paper is to analyze both numerically and experimentally the heat affected zone in tissue phantoms irradiated with a mode-locked short pulse laser source. It is only by being able to predict reliably the resultant temperature field that necessary dose for desired therapeutic outcomes can be ensured. A multi layer model of the skin consisting of the outer skin layer (epidermis), the lower layer (dermis) and fatty tissue underneath is considered in this study. Each layer of tissue has different optical properties. The experimentally measured temperature profiles for layered phantoms are compared with the homogenous phantoms using the non-Fourier hyperbolic and Fourier parabolic heat conduction model.

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