Tuning refractive index of PDMS by CO2 laser engraving for polymer optical splitter applications

•PDMS-based polymer optic power splitter with 1.0 mm and 400 μm core size.•CO2 laser pulses on PDMS surface for modification of chemical structure.•Refractive index alteration by CO2 laser pulses.•NOA 74 optical adhesive as a core material for both 1.0 mm and 400 μm core engraved PDMS. This work demonstrated the core cavity fabrication of apolymer optical power splitter by CO2 laser engraving. CO2 laser pulses radically modified the surface of PDMS by generating chemical changes. The prepared PDMS sheet was engraved with aCO2 laser at different pulse speeds to carve the surface with thedesired depth and width (1.0 mm and 400 µm) causing a chemical change introducing different functional groups on the surface of PDMS due to the oxidation of the surface during laser treatment. More importantly, therefractive index value of the pristine PDMS varied dramatically by the laser treatment. Employing NOA 74 optical adhesive as a core material on the CO2 engraved surface resulted in a polymer optical splitter with 1.0 mm and 400 µm of core size.