Effects of thermal treatment on femtosecond laser fabricated diffraction gratings in polystyrene

► Fabrication of efficient diffraction gratings, micro-craters are reported in bulk polystyrene. ► A maximum diffraction efficiency of 10% is reported for a buried grating fabricated at 1 μJ energy, 1 mm/s speed, and a period of 30 μm. ► FESEM and the Raman studies confirmed that the emission from the modified regions is due to optical centers created in the laser irradiated regions and the debris. ► Increase in emission and excitation intensities due to thermal treatment given to these gratings is presented. ► Raman analysis of different modes before and after irradiation indicated disappearance and intensity change for few modes at higher irradiation doses.