Poly(methylmethacrylate) (PMMA) has been a good prospect for the development of fully amorphous and highly transparent microphotonic devices. The possibilities of a hot embossing technique for the polymeric fabrication of optical waveguides were investigated in this work. A new technique based on radiofrequency plasma treatment was studied for thermal and optical properties, including glass transition temperature, thermal stability, refractive index, and optical transmission loss of PMMA. It is shown that the plasma treatment is effective in altering the functional groups of polymer surfaces without affecting the bulk properties, resulting in effective control of refractive indices and optical transmission losses for photonic applications.