Laser beam reflection by nano-designed two-layer nanostructured carbonic material formed in transparent hydrocarbon polymer by ion implantation

摘要

We investigated laser beam reflection by optically-transparent hydrocarbon polymeric material subjected to low-energyion implantation. In our study were measured 5 mm-thick plates of polymethylmethacrylate (PMMA) implanted withsilicon ions (Si~+) accelerated to a relatively low energy of 50 keV at Si~+ fluence of 1016 ions/cm2. Due to ion-produceddestruction of the polymer network and reorganization of the organic structure in a depth of PMMA plate, a buried ionmodifiedlayer with ～ 80 nm thickness is formed within the PMMA. The material in this ultra-thin nano-sized layerbeneath the top surface of PMMA (in a depth of v 100 nm) is organized in carbon nanoclusters with a mean size of about2 - 3 nm. The nonlinear gradual in-depth distribution of the complex refractive index in the nanostructured region of thepolymer results in a significant modification of the reflection of coherent light by the formed structure. Also, thereflected beam undergoes a strong laser-induced photothermal interface lensing upon irradiation by CW laser (? = 532nm) with an optical power above 30 mW. The presence of thermo-lenses can limit the optical and photonic applicationsof transparent ion-implanted polymers. Here, this negative effect is studied as dependent on both incident laser powerand incidence angle of the laser beam.