<p>A method is proposed for creating an optical profile diffraction grating consisting of nanoporous germanium (Ge) layers by sputtering a single-crystal c-Ge substrate by Bi⁺ ions at energy E = 18 keV, ion beam current density J = 5 μA/cm², and dose range D = 2.5·10¹⁶–1.0∙10¹⁷ ions/cm² through a copper mesh mask with square cells with length 20 μm. During the ion sputtering, cGe is sputtered in unmasked areas of the irradiated c-Ge leading to formation of a nanoporous Bi:PGe layer. The formation of periodic Bi:PGe microstructures on the c-Ge surface was monitored using optical, electron, and probe microscopy. The operation of this diffraction grating was demonstrated by probing it with helium-neon laser radiation at wavelength 632.8 nm in the optical spectral range.</p>