Photoinduced GRIN lens formation in chalcogenide Ge-As-S thin films

Abstract

We describe the photo induced formation of gradient index (GRIN) lenses in thin films of chalcogenide glass (ChG) of Ge₂₅As₃₀S₄₅ composition. We examine the changes of thickness of these samples by DekTak profilometry, as well as the optical performance and wave front distortions of the obtained lenses by using a Shack Hartmann sensor. The GRIN formation is related to the photo induced shift of the band gap towards shorter wavelengths (so-called photo-bleaching effect). The corresponding photo-induced birefringence of this material is in the origin of anisotropic GRIN lenses formed [1].