The optical reflectivity (both specular and off-specular) of poly(methyl methacrylate) (PMMA) implanted with silicon ions (Si+) at energy of 50 keV, is studied in the spectral range 0.25-25 mu m. The effect from the Si+ implantation on the reflectivity of two PMMA materials is examined in the dose range from 10(14) to 10(17) ions/cm(2) and is linked to the structure formed in this ion implanted plastic. As compared to the pristine PMMA, an enhancement of the reflectivity of Si+ implanted PMMA is observed, that is attributed to the modi. cation of the subsurface region of PMMA upon the ion implantation. The ion-produced subsurface organic interface is also probed by laser-induced thermo-lens. (C) 2009 Elsevier B. V. All rights reserved.