In this study we explore the possibility of using the process of electron-positron pair creation
in strong laser fields as a tool for measuring the intensity of the corresponding laser radiation. In
the initial state we consider either free electron gas or gas of neutral xenon, the electrons of which
get ionized. Once these seed electrons gain sufficient energy in the external laser field, they can
emit high-energy photons which subsequently decay producing electron-positron pairs via the BreitWheeler mechanism. By detecting the resulting positrons, one can recover the value of the laser
intensity by means of the one-to-one correspondences deduced in the present investigation. We
analyze two different configurations of the external field: the setup involving an individual focused
laser pulse and the combination of two counterpropagating laser pulses. Performing numerical
calculations and analyzing their accuracy, we demonstrate that based on our estimates, the laser
intensity can be determined within the range 1023–1026 W/cm2 with a relative uncertainty of 10–
50%.