Time-resolved measurements of optical properties in ultrafast laser interaction with polypropylene

Time-resolved, single-shot measurements are performed to determine the reflectance, transmittance, and absorptance in ultrafast laser interaction with polypropylene for a wide range of laser pulse energies. An ellipsoidal mirror is used to collect the majority of the reflected light, enabling the detection of plasma emission starting at about 40 ns after the incident pulse. The measured transmittance is explained by a model that takes into account different effective absorption channels, and the non-linear absorption coefficient is estimated, which suggests that the non-linear absorption originates from the two-step or two-photon absorption through overtone. The results are useful for selecting laser parameters in the processing of polymeric materials.