Comments on: Line broadening by focusing; Gas ionization by focused laser beams

1985 ◽  
Vol 63 (7) ◽  
pp. 1013-1013
Author(s):  
F. L. Curzon
Keyword(s):  
Laser Beam ◽  
Frequency Spectrum ◽  
Laser Beams ◽  
Line Broadening ◽  
Gas Ionization ◽  
On Line ◽  
Normal Lens ◽  
Focused Laser Beams

It is pointed out that the frequency spectrum of a laser beam is not broadened when the beam is focused by a normal lens. This assertion contradicts the conclusion reached by the authors of the articles cited in the title above.

Gas ionization by focused laser beams

1984 ◽  
Vol 62 (10) ◽  
pp. 1010-1013 ◽  
Author(s):  
A. L. de Brito
Keyword(s):  
Laser Radiation ◽  
Photon Energy ◽  
Ionization Energy ◽  
Laser Beams ◽  
Line Broadening ◽  
Gas Ionization ◽  
The Mean ◽  
Gas Molecules ◽  
Focused Laser Beams

It is shown that the effect of line broadening by focusing may contribute considerably to the observed laser-induced ionization of gases even when the ionization energy of the gas molecules is well above the mean photon energy of the laser radiation.

scholarly journals Accurate model for the ultra-relativistic interactions between laser beams and electrons

2020 ◽  
Vol 38 (4) ◽  
pp. 259-268
Author(s):  
Alexandru Popa
Keyword(s):  
Laser Beam ◽  
Frequency Spectrum ◽  
Relativistic Effects ◽  
Experimental Results ◽  
Laser Beams ◽  
Accurate Model ◽  
Large Frequency ◽  
Good Agreement

AbstractWe present an accurate approach of the basic ultra-relativistic effects which occur at the interactions between laser beams and electrons and correspond to laser beam intensities greater than 1020 W/cm2. These effects are the generation of extremely bright pulses and the existence of a very large frequency spectrum of the radiation generated by this interaction, containing relative intense harmonics of orders higher than 800. Our results are in good agreement with the experimental results published in the literature.

scholarly journals A critical look at the prediction of the temperature field around a laser-induced melt pool on metallic substrates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yi Shu ◽  
Daniel Galles ◽  
Ottman A. Tertuliano ◽  
Brandon A. McWilliams ◽  
Nancy Yang ◽  
...  
Keyword(s):  
Laser Beam ◽  
Constant Velocity ◽  
Three Dimensional ◽  
Laser Beams ◽  
Poor Control ◽  
Metallic Substrates ◽  
Melt Pool ◽  
Mechanical Models ◽  
Transport Effects ◽  
Thermal Histories

AbstractThe study of microstructure evolution in additive manufacturing of metals would be aided by knowing the thermal history. Since temperature measurements beneath the surface are difficult, estimates are obtained from computational thermo-mechanical models calibrated against traces left in the sample revealed after etching, such as the trace of the melt pool boundary. Here we examine the question of how reliable thermal histories computed from a model that reproduces the melt pool trace are. To this end, we perform experiments in which one of two different laser beams moves with constant velocity and power over a substrate of 17-4PH SS or Ti-6Al-4V, with low enough power to avoid generating a keyhole. We find that thermal histories appear to be reliably computed provided that (a) the power density distribution of the laser beam over the substrate is well characterized, and (b) convective heat transport effects are accounted for. Poor control of the laser beam leads to potentially multiple three-dimensional melt pool shapes compatible with the melt pool trace, and therefore to multiple potential thermal histories. Ignoring convective effects leads to results that are inconsistent with experiments, even for the mild melt pools here.

scholarly journals Investigation of serial coherent laser beam combination based on Brillouin amplification

2007 ◽  
Vol 25 (1) ◽  
pp. 79-83 ◽  
Author(s):  
SHUANGYI WANG ◽  
ZHIWEI LÜ ◽  
DIANYANG LIN ◽  
LEI DING ◽  
DONGBIN JIANG
Keyword(s):  
Laser Beam ◽  
High Power ◽  
Simple Structure ◽  
Low Cost ◽  
Coupling Efficiency ◽  
Laser Beams ◽  
Beam Combination ◽  
Multiple Beams ◽  
Combination Scheme ◽  
Stokes Beam

Based on transferring energy from multiple pump beams into one Stokes beam using Brillouin amplification, a serial coherent laser beam combination scheme is presented, which has many advantages, such as, simple structure, low cost, ease of adjustment, higher load capability, scalable easily, etc. Furthermore, it has been demonstrated that the combination of several beams using this method is theoretically possible. But in practice, the amplification of high power Stokes beam is a key problem to solve. In this paper, the amplification of Stokes beam whose power is higher than the pump beam is first studied and proved experimentally. Coupling the two laser beams by this method is proved experimentally, and the coupling efficiency reaches more than 80%. Then the feasibility of multiple beams combination based on Brillouin amplification is analyzed and tested theoretically.

Relativistic self-focusing of a rippled laser beam in a plasma

1999 ◽  
Vol 62 (4) ◽  
pp. 389-396 ◽  
Author(s):  
M. V. ASTHANA ◽  
A. GIULIETTI ◽  
DINESH VARSHNEY ◽  
M. S. SODHA
Keyword(s):  
Refractive Index ◽  
Laser Beam ◽  
The Self ◽  
Laser Beams ◽  
Radial Dependence ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Saturation Effects ◽  
Paraxial Ray

This paper presents an analysis of the relativistic self-focusing of a rippled Gaussian laser beam in a plasma. Considering the nonlinearity as arising owing to relativistic variation of mass, and following the WKB and paraxial-ray approximations, the phenomenon of self-focusing of rippled laser beams is studied for arbitrary magnitude of nonlinearity. Pandey et al. [Phys. Fluids82, 1221 (1990)] have shown that a small ripple on the axis of the main beam grows very rapidly with distance of propagation as compared with the self-focusing of the main beam. Based on this analogy, we have analysed relativistic self-focusing of rippled beams in plasmas. The relativistic intensities with saturation effects of nonlinearity allow the nonlinear refractive index in the paraxial regime to have a slower radial dependence, and thus the ripple extracts relatively less energy from its neighbourhood.

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