Influence of the wavelength for infrared laser effects on metals and dielectrics

Two high power mid-IR gas lasers, the CO laser and the chemical HF laser, can offer higher absorption for metals and better focusing, i.e. smaller spot areas than CO2 and Nd:YAG lasers. A comparison of the effects of three gas lasers is carried out at the ISL, using three high-power gas lasers: 1 kW (HF), 6 kW (CO) and 7.5 kW (CO2) and allows to compare their effects on different materials. The absorptivity of these laser beams for several metals has been measured, both with low energy measurement techniques and with high power laser beams; an increase in absorptivity has been demonstrated for the short wavelengths lasers. Plexiglass irradiated with these lasers beams exhibits a boiling-type destruction behavior. The threshold fluence for the occurrence of the bubbles has been measured and compared with a simple boiling model showing the importance of the spectral absorption coefficient.