The effect of silicon ion implantation on the optical reflection of bulk polymethylmethacrylate (PMMA) was examined in the visible and near UV. A low-energy (30 and 50 keV) Si+ beam at fluences in the range from 10(13) to 10(17) cm(-2) was used for ion implantation of PMMA. The results show that a significant enhancement of the reflectivity from Si+-implanted PMMA occurs at appropriate implantation energy and fluence. The structural modifications of PMMA by the silicon ion implantation were characterized by means of photoluminescence and Raman spectroscopy. Formation of hydrogenated amorphous carbon (HAC) layer beneath the surface of the samples was established and the corresponding HAC domain size was estimated. (C) 2008 Elsevier B.V. All rights reserved.