  In the ultraintense laser-solid interaction, our recent work [Phys. Rev. E
109, 035204 (2024)] has revealed that the linear Breit-Wheeler (BW) process via
photon-photon collisions will become the dominant mechanism for
electron-positron pair production at the normalized laser amplitude
$a_0<400$--$500$. Here, we investigate the impact of photon polarization on
linear Breit-Wheeler pair production in the similar laser-solid setup, mainly
focusing on the difference of positron yields between polarized and unpolarized
situations. Two facts serve as the motivation for this work: (i) the emitted
photons via nonlinear Compton scattering are highly linearly polarized in the
strong-field QED regime; (ii) the linear BW cross section
$\sigma_{\gamma\gamma}$ is dependent on photon polarization. By using
two-dimensional QED particle-in-cell simulations, we find that the photon
polarization effect can suppress the positron yield by 5% to 10% in linear BW
pair production. This is because the polarization directions of colliding
photons are predominantly parallel, resulting in a reduced
$\sigma_{\gamma\gamma}$ compared to the unpolarized cross section. The
suppression degree is decreased with the enhancement of the nonlinear QED
strength at higher laser intensities. This work emphasizes the importance of
photon polarization in accurately predicting linear BW pair production in
laser-driven plasmas.
