An investigation of the mechanism of the W laser induced temperature field in a PETP-polymer is presented. We discuss a specific mathematical solution of the heat equation for large-area (uniform) irradiation on the PETP-substrate in relation to laser and substrate parameters. Depending on the order of magnitude of the absorption coefficient of the polymer for different UV-light surface temperatures of approx. 16,000 degreesC (193 nm), 11,000 degreesC (248 nm) and 520 degreesC (308 nm) are calculated by simulation at the end of the laser pulse, The temperature input within the polymer layer is limited to only a very small penetration depth (< 0.4 m at 193 nm, 248 nm and < 8 m for 308 nm). Besides the effect of surface structuring, material ablation processes also occur simultaneously during laser irradiation, Theoretically calculated results of the material removal depth on the PETP-polymer agree largely with the experiments.