  The creation of an electron-positron pair in the collision of two real
photons, namely the linear Breit-Wheeler process, has never been detected
directly in the laboratory since its prediction in 1934 despite its fundamental
importance in quantum electrodynamics and astrophysics. In the last few years,
several experimental setup have been proposed to observe this process in the
laboratory, relying either on thermal radiation, Bremsstrahlung, linear or
multiphoton inverse Compton scattering photons sources created by lasers or by
the mean of a lepton collider coupled with lasers. In these propositions, the
influence of the photons' energy distribution on the total number of produced
pairs has been taken into account with an analytical model only for two of
these cases. We hereafter develop a general and original, semi-analytical model
to estimate the influence of the photons energy distribution on the total
number of pairs produced by the collision of two such photon beams, and give
optimum energy parameters for some of the proposed experimental configurations.
Our results shows that the production of optimum Bremsstrahlung and linear
inverse Compton sources are, only from energy distribution considerations,
already reachable in today's facilities. Despite its less interesting energy
distribution features for the LBW pair production, the photon sources generated
via multiphoton inverse Compton scattering by the propagation of a laser in a
micro-channel can also be interesting, thank to the high collision luminosity
that could eventually be reached by such configurations. These results then
gives important insights for the design of experiments intended to detect
linear Breit-Wheeler produced positrons in the laboratory for the first time.
