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).

Simulation Based Study on Ultra-Short Pulse Laser Welding of Dissimilar Materials Expending Phase Lag Influence

2017 ◽  
Author(s):  
Swarup Bag ◽  
M. Ruhul Amin
Keyword(s):  
Heat Transfer ◽  
Pulse Laser ◽  
Short Pulse ◽  
Relaxation Times ◽  
Heat Transfer Analysis ◽  
Phase Lag ◽  
Short Pulse Laser ◽  
Simulation Based ◽  
Ultra Short Pulse ◽  
Ultra Short Pulse Laser

In this work, the thermal simulation of dissimilar fusion welding system is demonstrated by considering the phase lag effects in ultra-short pulse laser source. When the pulse duration is comparable with the electron relaxation time, the hyperbolic effect cannot be neglected in heat transfer analysis due to femtosecond laser. The non-Fourier effect is considered for heat transfer analysis assuming finite delay in development of temperature within the body. This delay is represented in terms of relaxation times connected to heat flux and temperature gradient. In the present work, the simulation has been proposed by developing 3D finite element based heat transfer model using dual phase lag effect. Since the experimental basis of transient temperature distribution in ultra-short pulse laser is extremely difficult or nearly impossible, the model results have been validated with literature reported results. The model has been used further for the simulation of temperature distribution in femtosecond fiber laser welding of dissimilar aluminum alloy and stainless steel. The results in terms of computed isotherm are compared with experimentally evaluated weld pool geometry for dissimilar materials from independent literature. The influence of other characteristic parameters like pulse frequency, pulse width and relaxation times are assessed for this simulation based study which will effectively reduce the costly experimental effort for differential influence of process parameters. A clear guideline of geometric shape and size of weld pool geometry and peak temperature of the welding system with reference to predictable laser parameters are the effective output of this simulation based study. It was observed that the peak temperature reached in a very short interval of time, in the order of nano-seconds. Such high heating or cooling rate impacts on the microstructural changes of the welded joint. In order to reach certain temperature, multiple pulses are required in the material processing of either very thin film or microwelding to keep the thermal shock distortion as low as possible.

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.

Ablation of Subsurface Tumors Using 1552 nm Ultra-Short Pulse Laser

2008 ◽  
Author(s):  
Shreya Raje ◽  
Amir Sajjadi ◽  
Kunal Mitra ◽  
Michael S. Grace
Keyword(s):  
Laser Beam ◽  
Pulse Laser ◽  
Continuous Wave ◽  
Short Pulse ◽  
Laser Source ◽  
Short Pulse Laser ◽  
Fiber Optic Probes ◽  
Laser Immunotherapy ◽  
Ultra Short Pulse ◽  
Long Pulse

Over last two decades lasers have been used for the treatment of subsurface tumors. Various techniques such as Laser-induced Hyperthermia, Laser Interstitial Thermal Therapy (LITT), and Laser Immunotherapy have been developed for the successful ablation of subsurface tumors by different researchers. All these techniques use photo-thermal mechanism for tumor ablation by delivering thermal energy at the tumor site. In all these existing techniques, either continuous wave (CW) or long pulse laser source has been used, which often produces larger heat affected zone as compared to that produced by short pulse laser. Moreover, the delivery of laser beam at the target site is achieved through fiber optic probes which often require perforation of the skin. These drawbacks can be eliminated if a converging laser beam from a short pulse laser source is directly focused at the subsurface location to ablate the tumor.

Silicon Thinning using Ultra-Short Pulse Laser Ablation

2004 ◽  
Author(s):  
F. Beaudoin ◽  
P. Perdu ◽  
C. DeNardi ◽  
R. Desplats ◽  
J. Lopez ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Sample Preparation ◽  
Pulse Laser ◽  
Pulse Laser Ablation ◽  
Short Pulse ◽  
Special Care ◽  
Short Pulse Laser ◽  
Ultra Short Pulse ◽  
Ultra Short Pulse Laser

Abstract Ultra-short pulse laser ablation is applied to IC backside sample preparation. It is contact-less, non-thermal, precise and can ablate the various types of material present in IC packages. This study concerns the optimization of ultra-short pulse laser ablation for silicon thinning. Uncontrolled silicon roughness and poor uniformity of the laser thinned cavity needed to be tackled. Special care is taken to minimize the silicon RMS roughness to less than 1µm. Application to sample preparation of 256Mbit devices is presented.

The study of time dependent, broadband X-ray emission from ultra-short pulse laser produced plasmas

1994 ◽  
Author(s):  
Ronnie Shepherd ◽  
Rex Booth ◽  
Dwight Price ◽  
Rosemary Walling ◽  
Richard More ◽  
...  
Keyword(s):  
Pulse Laser ◽  
Short Pulse ◽  
Time Dependent ◽  
X Ray ◽  
Short Pulse Laser ◽  
Ultra Short Pulse ◽  
Ultra Short Pulse Laser
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