  The photo-production of a pair of scalar particles in the presence of an
intense, circularly polarized laser beam is investigated. Using the optical
theorem within the framework of scalar quantum electrodynamics, explicit
expressions are given for the pair production probability in terms of the
imaginary part of the vacuum polarization tensor. Its leading asymptotic
behavior is determined for various limits of interest. The influence of the
absence of internal spin degrees of freedom is analyzed via a comparison with
the corresponding probabilities for production of spin-1/2 particles; the lack
of spin is shown to suppress the pair creation rate, as compared to the
predictions from Dirac theory. Potential applications of our results for the
search of minicharged particles are indicated.
