Design and optimisation of a pulsed CO2 laser for laser ultrasonics

Abstract

Laser ultrasonics is the present state-of-the art method for non-destructive testing of composite materials in the aerospace industry. The process is based on an IR laser generating an ultrasound wave that propagates inside the composite material, resulting in a response at the material surface. This is detected and converted into a defect map across the aircraft. In this paper the authors consider the design and optimisation of a laser system for this application, and cover the basic science encountered in the process, including gas breakdown, catalytic gas recombination theory, laser gain disturbances by acoustic waves, and temporal pulse optimisation. The authors present some new findings as well as the design of an operating laser system that shows an improvement in performance six times over in comparison to conventional laser systems for this application