The anisotropic optical properties of different polytypes (ε, β, δ, γ) of GaSe lamellar materialsMohamed Al-Hattab, Lhoucine Moudou, Younes Chrafih, Mohammed Khenfouch, Omar Bajjou and Khalid RahmaniEur. Phys. J. Appl. Phys., 91 3 (2020) 30102DOI: https://doi.org/10.1051/epjap/2020200136