Eur. Phys. J. Special Topics 153, 95-98 (2008)
https://doi.org/10.1140/epjst/e2008-00401-1

Effect of laser beam size on measurement contrast of thermophysical gradients in layered structures using thermal-wave techniques

¹ Institute of Modern Optical Technologies Suzhou University, Suzhou, Jiangsu 215006, P.R. China and Key Lab of Modern Optical Technologies of Jiangsu Province, Suzhou, Jiangsu, 215006, P.R. China
² Center for Advanced Diffusion Wave Technologies, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, M5S 3G8, Ontario, Canada

Abstract

The effect of the laser source spotsize on the measurement sensitivity of layered system using photothermal radiometry (PTR) technique is presented. The beam size effect on the PTR measurement sensitivity is theoretically examined and experimentally demonstrated using a carbo-nitrided C1018 steel sample. The experimental results using a focused beam and an expanded beam for a carbo-nitrided C1018 sample validated the theoretical prediction, according to which the expanded beam showed a much larger magnitude change (contrast) in both amplitude and phase than results with a focused beam.