Physical phenomena and their interpretation in laser materials processing

Abstract

The paper describes the energy dissipation mechanism during beam-plume/plasma interaction as the first part, and a simplified prediction model of temporal change in penetration depth of laser spot welding and hole drilling which is applicable to any pulse shape as the second part.From spectroscopic and other optical measurements of Tiplume induced by pulsed YAG laser shot, it has been concluded that major energy dissipation processes in plume are; 1) Absorption of photons in a plume/plasma by Inverse Bremsstrahlung, and 2) Rayleigh scattering of incident beam by ultra fine particles formed in the plume. Both processes have strong dependence on wave length of radiation and the paper gives the generalized idea of energy loss of laser beam in laser induced plume/plasma.In the second part, the temporal change in penetration depth of laser spot welding and hole drilling by pulsed YAG laser was measured by chopping the incident beam at arbitrary duration and the simplified one dimensional heat conduction model which was applicable to any pulse shape was proposed.The paper describes the energy dissipation mechanism during beam-plume/plasma interaction as the first part, and a simplified prediction model of temporal change in penetration depth of laser spot welding and hole drilling which is applicable to any pulse shape as the second part.From spectroscopic and other optical measurements of Tiplume induced by pulsed YAG laser shot, it has been concluded that major energy dissipation processes in plume are; 1) Absorption of photons in a plume/plasma by Inverse Bremsstrahlung, and 2) Rayleigh scattering of incident beam by ultra fine particles formed in the plume. Both processes have strong dependence on wave length of radiation and the paper gives the generalized idea of energy loss of laser beam in laser induced plume/plasma.In the second part, the temporal change in penetration depth of laser spot welding and hole drilling by pulsed YAG laser was measured by chopping the incident beam at arbitrary duration and the simplified one dimensional heat conduction model ...