We demonstrate the generation of high-energy \(\gamma\) -photons and pair electrons resulting from the interaction of an ultrahigh-intensity laser pulse with a near-critical density plasma target. Through polarization-resolved analysis and three-dimensional particle-in-cell simulations, we investigate how linearly and circularly polarized laser pulses differentially influence photon emission spectra, angular distributions, and pair-production. In our configuration, circular polarization yields higher-energy \(\gamma\) -photons, attributed to smoother electron trajectories and sustained interaction with the laser field. These \(\gamma\) -photons subsequently trigger the production of Breit–Wheeler pair electrons, whose efficiency is strongly dependent on both the laser intensity and the polarization state. This study highlights the potential of polarization shaping as a control tool for optimizing gamma-ray sources and QED pair plasma generation in next-generation ultraintense laser facilities.
