Three-dimensional tracking of small spheres in focused laser beams: influence of the detection angular aperture

2003 ◽  
Vol 28 (6) ◽  
pp. 411 ◽  
Author(s):  
Alexander Rohrbach ◽  
Holger Kress ◽  
Ernst H. K. Stelzer
Keyword(s):  
Three Dimensional ◽  
Laser Beams ◽  
Angular Aperture ◽  
Focused Laser Beams

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 Single particle scattering with focused laser beams

1977 ◽  
Vol 16 (4) ◽  
pp. 1104 ◽  
Author(s):  
Lee W. Casperson ◽  
C. Yeh ◽  
Wing F. Yeung
Keyword(s):  
Single Particle ◽  
Laser Beams ◽  
Particle Scattering ◽  
Focused Laser Beams

scholarly journals Three-Dimensional Skyrmions with Arbitrary Topological Number in a Ferromagnetic Spin-1 Bose-Einstein Condensate

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Huan-Bo Luo ◽  
Lu Li ◽  
Wu-Ming Liu
Keyword(s):  
Magnetic Field ◽  
Vortex Ring ◽  
Three Dimensional ◽  
Einstein Condensate ◽  
Laser Beams ◽  
Quantization Axis ◽  
Density Distributions ◽  
Bose Einstein Condensate ◽  
Bose Einstein ◽  
Topological Number

AbstractWe propose a new scheme for creating three-dimensional Skyrmions in a ferromagnetic spin-1 Bose-Einstein condensate by manipulating a multipole magnetic field and a pair of counter-propagating laser beams. The result shows that a three-dimensional Skyrmion with topological number Q = 2 can be created by a sextupole magnetic field and the laser beams. Meanwhile, the vortex ring and knot structure in the Skyrmion are found. The topological number can be calculated analytically in our model, which implies that the method can be extended to create Skyrmions with arbitrary topological number. As the examples, three-dimensional Skyrmions with Q = 3, 4 are also demonstrated and are distinguishable by the density distributions with a specific quantization axis. These topological objects have the potential to be realized in ferromagnetic spin-1 Bose-Einstein condensates experimentally.

Filamentation and Undulation of Self-Focused Laser Beams in Liquid Crystals

1993 ◽  
Vol 23 (4) ◽  
pp. 239-244 ◽  
Author(s):  
E Braun ◽  
L. P Faucheux ◽  
A Libchaber ◽  
D. W McLaughlin ◽  
D. J Muraki ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Laser Beams ◽  
Focused Laser Beams

scholarly journals Amplitude and Phase of Tightly Focused Laser Beams in Turbid Media

2009 ◽  
Vol 103 (4) ◽  
Author(s):  
Carole K. Hayakawa ◽  
Vasan Venugopalan ◽  
Vishnu V. Krishnamachari ◽  
Eric O. Potma
Keyword(s):  
Turbid Media ◽  
Laser Beams ◽  
Focused Laser Beams
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