Optical properties of Azo Dye (1-Phenylazo-2-Naphthol) thin filmsM. S. Aziz, H. M. El-Mallah and A. N. MansourEur. Phys. J. Appl. Phys., 48 2 (2009) 20401DOI: https://doi.org/10.1051/epjap/2009137