The effect of Er on optical and mechanical properties of As2S3 glasses quenched in different media Mohammad Rezvani, Amin Yousefi Dizaj, Ali Rahimian and Tohid Joudi Eur. Phys. J. Plus, 135 6 (2020) 532 Published online: 29 June 2020 DOI: 10.1140/epjp/s13360-020-00502-9