The high power multimode fiber-coupled laser sources, like solid state lasers or laser diodes as well as single mode and multimode fiber lasers, are now widely used in various industrial laser material processing technologies like metal or plastics welding, cladding, hardening, brazing, annealing. Performance of these technologies can be essentially improved by varying the irradiance profile of...

the rapid melting of a semi- infinite body due to the absorption of a cw laser beam radiation has been studied. the enthalpy technique for the solution of phase change problems has been used in an explicit finite difference form to calculate the transient temperature distribution in the semi-infinite body and the growth rate of the melt pool. the technique has been modified so that it is not ne...

LLE Review, Volume 98 49 Introduction A direct-drive inertial confinement fusion (ICF) implosion of a spherical capsule containing thermonuclear fuel is initiated by the ablation of material from the outer shell surface with overlapped, intense laser beams.1 The ablated shell mass forms a coronal plasma that surrounds the target and accelerates the shell inward via the rocket effect.1,2 Perturb...

In the laser deposition of single crystal and directionally-solidified superalloys, it is desired to form laser deposits with high volume fractions of columnar grains by suppressing the columnar-to-equiaxed transition efficiently. In this paper, the influence of beam profile (circular and square shapes) and cooling conditions (natural cooling and forced cooling) on the geometric morphology and ...

We report results of the study of soft-x-ray amplification in a discharge-created plasma under an externally applied axial magnetic field. This technique is observed to improve the uniformity and divergence of the beam of a 46.9-nm discharge-pumped Ne-like Ar soft-x-ray amplifier by decreasing the plasma density gradients at the time of lasing. At the optimum strength of 0.15 T, the magnetic fi...

We consider the effect of laser beam shaping on proton acceleration in the interaction of a tightly focused pulse with ultrathin double-layer solid targets in the regime of directed Coulomb explosion. In this regime, the heavy ions of the front layer are forced by the laser to expand predominantly in the direction of the pulse propagation, forming a moving longitudinal charge separation electri...

A theoretical model is presented and experimentally validated that allows the prediction of the effect of speckles on the depth sensitivity of laser Doppler perfusion imaging. It is shown that the influence of speckles on depth sensitivity is large. In particular the sensitivity to particle motion in superficial layers is strongly beam diameter dependent: decreasing the beam diameter on the tis...

If a heated pipe is rotated about its axis, a density gradient is formed which results in the pipe acting as a graded index lens. In this study we revisit the concept of a spinning pipe gas lens and for the first time analyse both the wave propagation of optical fields through the lens, and determine the optical aberrations introduced by the lens to the laser beam. We show that such lenses are ...

The effect of the microstructure on transversely coupled laser light into the core of a photonic crystal fiber is investigated. Computational two-dimensional modeling and direct experimental measurements indicate that there exist angles and positions of the fiber microstructure, relative to a transversely launched laser beam, that preferentially couple laser light into the fiber core. The impli...