Fabrication of Optical Microstructures with Gradient Refractive Index by Two-Photon Laser Lithography. - Aparin, M. D.; Baluyan, T. G.; Sharipova, M. I.; Sirotin, M. A.; Lyubin, E. V.; Soboleva, I. V.; Bessonov, V. O.; Fedyanin, A. A. (Bulletin of the Russian Academy of Sciences: Physics, 2023)