Monocrystalline silicon (Si or c-Si) is of paramount importance for modern optoelectronics, yet its centrosymmetric crystal lattice restricts any inherent optical anisotropy. This fundamental limitation precludes construction of polarization-sensitive Si-based photodetectors (PD) relevant for bioimaging, information encryption and ellipsometry. In this work, we used laser-induced periodic surface structuring (LIPSS) to directly imprint optically anisotropic nanogratings with a periodicity around 270 nm over the active area of a vertical p–n junction Si PD. Sensitivity to polarization of the incident radiation was observed within 700–1100 nm spectral range with a photoresponse modulation up to 80% for the cross-polarized light under zero bias conditions. Defect-mediated absorption within laser-patterned layer was found to expand operation range of the PD rendering it with ability to detect photons with sub-band gap energies (up to 1400 nm), while causing no crucial degradation of dynamic characteristics and photoresponse of the self-powered device within common operation window. Under a small reverse bias of 1 V, the LIPSS-patterned PD provides cross-polarized photoresponse modulation up to 430% surpassing 100% external quantum efficiency benchmark under optimal excitation. Importantly, such competitive device performance was achieved through facile upscalable procedure without hyperdoping requiring expensive gas chambers and toxic chemicals.