Study of the influence of the Nd:YAG laser irradiation at 1.3 μm on the thermal-mechanical-optical parameters of germanium

An original compact test method of studying the influence of a modified Nd:YAG laser beam irradiation at the unusual wavelength of λ=1.3μm on different types of IR-Ge-windows (single- and polycrystal, n-doped, p-doped or without doping) is investigated: optical parameters such as transmission loss, surface temperature during the laser irradiation, morphological deformation, and damage thresholds are measured in real time and compared with theoretical simulations. To study the thermal-mechanical relationship of the laser-matter interaction, an original pyrometer array is developed for the temperature-profile measurement and an original deformation experimental set-up, including a “line generator”, is introduced. The damage behaviour of the different types of germanium at the wavelength of λ=1.3μm is also presented in this paper.