Optical properties of Azo Dye (1-Phenylazo-2-Naphthol) thin films M. S. Aziz, H. M. El-Mallah and A. N. Mansour Eur. Phys. J. Appl. Phys., 48 2 (2009) 20401 Published online: 17 September 2009 DOI: 10.1051/epjap/2009137