Stability and performance of laser technologies based on high power lasers depend on possibility to control the thermally induced optical effects: thermal focus shift and thermally induced aberrations. Even if the thermal focus shift is compensated, for example by mechanical movement of a processing head, the thermally induced aberration can be a reason of essential variation of intensity distribution and, hence, degradation of a process performance. This aberration effect is especially important in applications presuming use of beam shaping optics and lasers of high optical quality, for example powerful TEM00 lasers for Selective Laser Melting (SLM) or remote welding. Analysis of optical effects happening due to gradient heating of optical components shows that aberrations are mainly issued by change of geometrical shape of optical surfaces (bulge) and appearing the gradient of refractive index. Both effects thermal focus shift and thermally induced aberrations have the same nature. Therefore, to avoid appearing of those effects it is suggested to apply optical components made from special optical materials with athermal properties where geometrical and refractive optical effects compensate each other, then influence of unwished thermal effects can be strongly reduced. There will be presented analysis of thermally induced aberrations appearing in protective windows made from different optical materials: fused silica, N-BK7 glass, aThermoXX glass. Comparison of simulation results and experimental data confirm effectiveness of the suggested approach.