Laser beam shape

Laser Beam Shaping, Fred M. Dickey and Scott C. Holswade... 

Laser Beam Shaping Applications, edited by Fred M. Dickey, Scott C. Holswade and David L. Shealy... 

Here, the proportionality constant Kd is a function of the geometry of the calorimeter and other instrument parameters (e.g., laser beam shape and its position relative to the transducer). 

Entropy and Information Optics, FrancisT. S. Yu Computational Methods for Electromagnetic and Optical Systems, John M. Jarem and Partha P. Banerjee Laser Beam Shaping, Fred M. Dickey and Scott C. Holswade Rare-Earth-Doped Fiber Lasers and Amplifiers Second Edition, Revised and Expanded, edited by Michel J. F. Digonnet Lens Design Third Edition, Revised and Expanded, Milton Laikin Handbook of Optical Engineering, edited by Daniel Malacara and Brian J. Thompson... 

Dickey FM et al (eds) (2006) Laser beam shaping applications. Taylor and Francis, UK Dini JW (1993) Electrodeposition the materials science of coatings and substrates. Noyes, NJ Drobny JG (2001) Technology of fluoropolymers. CRC, Boca Raton Drobny JG (2003) Radiation technology for polymers. CRC, Boca Raton Esquivias L (ed) (2009) Progress in sol-gel production special topic volume with invited papers only. Trans Tech Publications, Switzerland... 

This paper deals with the control of weld depth penetration for cylinders in gold-nickel alloy and tantalum. After introducing the experimental set-up and the samples description, the study and the optimization of the testing are presented for single-sided measurements either in a pulse-echo configuration or when the pump and the probe laser beams are shifted (influence of a thermal phenomenon), and for different kind of laser impact (a line or a circular spot). First, the ultrasonic system is used to detect and to size a flat bottom hole in an aluminium plate. Indeed, when the width of the hole is reduced, its shape is nearly similar to the one of a slot. Then, the optimization is accomplished for... 

Particle Size. Wet sieve analyses are commonly used in the 20 )J.m (using microsieves) to 150 )J.m size range. Sizes in the 1—10 )J.m range are analyzed by light-transmission Hquid-phase sedimentation, laser beam diffraction, or potentiometric variation methods. Electron microscopy is the only rehable procedure for characterizing submicrometer particles. Scanning electron microscopy is useful for characterizing particle shape, and the relation of particle shape to slurry stabiUty. 

Usually, particle size has relatively little effect on Raman line shapes unless the particles are extremely small, less than 100 nm. For this reason, high-quality Raman spectra can be obtained from powders and from polycrystalline bulk specimens like ceramics and rocks by simply reflecting the laser beam from the specimen surface. Solid samples can be measured in the 90° scattering geometry by mounting a slab of the solid sample, or a pressed pellet of a powder sample so that the beam reflects from the surface but not into the entrance slit (Figure 3). 

A very important characteristic of laser radiation is the beam shape. So far most LA experiments have been performed with Gaussian laser beams. Lasers with uniform distribution of the beam cross-section have been used only recently to achieve high lateral and depth resolution. Specially designed beam homogenizers must be used for this purpose [4.226-4.228]. The Cetac LSX-200 system has a flat-top distribution of the laser beam. 

The crater surfaces obtained in the LA-TOF-MS experiment on the TiN-TiAlN-Fe sample were remarkably smooth and clearly demonstrated the Gaussian intensity distribution of the laser beam. Fig. 4.45 shows an SEM image of the crater after 100 laser pulses (fluence 0.35 J cm ). The crater is symmetrical and bell-shaped. There is no significant distortion of the single layers. Fig. 4.45 is an excellent demonstration of the potential of femtosecond laser ablation, if the laser beam had a flat-top, rather than Gaussian, intensity profile. 

The peak surface temperature under the center of the laser beam is 990 C above the starting surface temperature. The detailed temporal shape of the surface temperature will depend on the detailed time profile of the laser pulse. However, two Important characteristics of the temperature jump which is generated will be retained ... 

The radiation can be amplified by an optical resonator, which, in the simplest case, is constituted by the semiconductor itself, shaped in the appropriate manner for instance, by cutting the crystal so that two end faces are parallel to each other, and exactly perpendicular to the laser beam emitted by the junction (see Fignre 2.14). 

A. Larsson, N. Eriksson, S. Kristjansson, P. Modh, M. Uemukai, T. Suhara, and H. Nishihara, Grating coupled surface emitters integrated lasers, amplifiers, and beam shaping outcouplers, SPIE 3626, 190-200 (1999). 

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