An investigation into random lasing from thin film on a sandpaper substrate Zhi Ren, Ping Wang, Kun Ge, Yang liu, Guiyin Zhang, Zongli Sun and Songtao Li Eur. Phys. J. D, 74 3 (2020) 53 Published online: 19 March 2020 DOI: 10.1140/epjd/e2020-100484-0