Thermal mechanisms of laser marking in transparent polymers with light-absorbing microparticles

• This work is focused on the formation of laser-induced marks in transparent polymers activated by light-absorbing microparticles.
• White- and dark-colored marks have been observed.
• Generation of laser-induced marks is accompanied by laser-induced incandescence.
• Laser-induced incandescence of laser-heated objects provides information about processes that occur in material substance under laser irradiation.

Interaction of highly viscous polystyrene suspensions of light-absorbing microparticles with pulsed radiation of a Q-switched YAG:Nd3+ laser is investigated. Absorption of laser radiation by the suspended microparticles causes thermal decomposition (pyrolysis) of the polymer in the vicinity of the overheated particles. Laser-induced incandescence (LII) of light-absorbing microparticles under irradiation by a sequence of laser pulses is observed. The mechanism of laser marking includes formation of light-absorbing and scattering centers by accumulation of carbonaceous and gaseous products of pyrolysis.