Germanium wafer surface is modified by a technique of CO2-laser induced air breakdown processing, which was recently introduced and used to produce photoluminescent Si-based nanostructured layers. Structural and optical properties of the Ge-based layers, formed under the irradiation spot as a result of the processing, are characterized by different techniques (SEM, XPS, FTIR, XRD, and PL). It has been found that the layers present a porous structure, containing nanoscale holes, and consist of Ge nanocrystals embedded into GeO2 matrices. They exhibited strong photoluminescence (PL) in the green range (2.2 eV), which was attributed to defects in GeO2 matrix due to the presence of Ge-O modes with some OH vibration in the FTIR spectra. The layers are of importance for local patterning of nanostructures on semiconductors.