Acoustic diagnostics of the explosive boiling up of a transparent liquid on an absorbing substrate induced by two nanosecond laser pulses

Photoacoustic pressure signals produced in an absorbing substrate under a layer of a transparent liquid irradiated by two successive nanosecond laser pulses are studied experimentally. The first pulse causes the heating and explosive boiling up of the liquid layer in contact with the irradiated surface, while the second pulse reaches the target at the time when a vapour film has already formed on its surface. The second photoacoustic response contains additional information on heat-and-mass transfer between the liquid and substrate surfaces separated by the vapour film.