A novel photo-thermal setup for evaluation of absorptance losses and thermal wavefront deformations in DUV optics

For an assessment of the optical quality of DUV optics, a high-sensitivity wavefront analyzer system based on the Hartmann-Shack principle is employed. The device accomplishes precise on-line monitoring of wavefront deformations of a collimated test beam transmitted through the laser-irradiated site of a sample. Due to the achieved sub-nm resolution, it can be used as an alternative to calorimetric and interferometric measurements for 'at wavelength' testing of optics, e.g. for on-line registration of thermal lensing effects or compaction in fused silica. By recording wavefront distortions of fused silica samples of different thickness and at different fluences the contribution of bulk and surface to the total absorption as well as one- and two-photon effects can be separated.