Ultrathin nano-ring metasurface absorber in visible regime based on circuit model Seyedeh Leila Mortazavifar, Mohammad Reza Salehi and Mojtaba Shahraki Eur. Phys. J. Plus, 137 9 (2022) 1072 Published online: 20 September 2022 DOI: 10.1140/epjp/s13360-022-03272-8