Coherent Phonon Materials for Laser Applications

1993 ◽  
Vol 329 ◽  
Author(s):  
T. K. Cheng ◽  
J. Vidal ◽  
H. J. Zeiger ◽  
E. P. Ippen ◽  
G. Dresselhaus ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Short Pulse ◽  
Laser Source ◽  
Coherent Phonon ◽  
Lattice Vibrations ◽  
Narrow Gap ◽  
Light Modulator ◽  
Laser Applications ◽  
Short Pulse Laser ◽  
The Time Domain

AbstractWith the development of the short pulse laser source, it has been demonstrated that molecular [1–4] and lattice dynamics [5–7] can be studied in the time domain. Pulses of light that are short compared to the optical phonon period have been found to initiate coherent lattice vibrations through various mechanisms which depend on the material type. The purpose of this paper is to describe the observation of the coherent phonon phenomenon in semimetals and narrow-gap semiconductors, and to propose a potential application of this phenomenon as a terahertz light modulator.

scholarly journals Surface Exposure Technology of Metal Powder Based on an Optically-Addressed Liquid Crystal Spatial Light Modulator

2021 ◽  
Vol 11 (8) ◽  
pp. 3647
Author(s):  
Ying Cai ◽  
Dajie Huang ◽  
He Cheng ◽  
Gang Xia ◽  
Wei Fan
Keyword(s):  
Liquid Crystal ◽  
Additive Manufacturing ◽  
Spatial Light Modulator ◽  
Short Pulse ◽  
Processing System ◽  
Damage Threshold ◽  
Laser Source ◽  
Light Modulator ◽  
Short Pulse Laser ◽  
Nanosecond Pulsed Laser

Compared with the current mature point scanning metal additive manufacturing technology, the surface exposure technology by laser additive manufacturing can accelerate the construction speed, and the short pulse laser is expected to improve the resolution. Here, a surface exposure technology processing system was constructed based on a nanosecond pulsed laser source and an optically-addressed liquid crystal spatial light modulator with a damage threshold higher than 500 mJ/cm2. The resolution of the surface exposure processing system is proved to be about 100 μm.

Yb doped Fluorides for High Power and Short-Pulse Laser Applications

2011 ◽  
Author(s):  
Frédéric Druon ◽  
Sandrine Ricaud ◽  
Dimitris N. Papadopoulos ◽  
Alain Pellegrina ◽  
Marc Hanna ◽  
...  
Keyword(s):  
Pulse Laser ◽  
High Power ◽  
Short Pulse ◽  
Laser Applications ◽  
Short Pulse Laser

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

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.

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).

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.

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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