Design of a low-cost laser CUT-OFF filters using carmine dye-doped PVA polymeric composite films

Abstract

Polyvinyl alcohol (PVA)/carmine dye polymeric composite films are prepared by a solution casting method. Pure PVA, 0.11 wt% carmine dye/PVA, 0.55 wt% carmine dye/PVA, 1.11 wt% carmine dye/PVA, 5.5 wt% carmine dye/PVA, 11.11 wt% carmine dye/PVA and 27.775 wt% carmine dye/PVA have a semi-crystalline structure. The transmission spectrum shows that the light is blocked till 600 nm for 27.775 wt% carmine dye/PVA composite films. The transmittance for the composite 27.775 wt% carmine/PVA is reduced to 61%. The absorption bands and band edges were shifted due to the increase of carmine dye percentage in the PVA matrix. The direct bandgap decreased from 5.16 to 1.65 eV as the carmine dye percentage increased.The indirect band gap decreased from 4.75 to 0.99 eV. The refractive index is strongly dependent on the amount of carmine dye on PVA, and the refractive index increased up to 8. The optical conductivity of PVA/carmine dye composites was divided into different stages according to the photon energy. The highest values of the dielectric loss for PVA/carmine dye composites were found at the lowest frequency (100 Hz). PVA/carmine dye composite films are promising standing up filters for laser power attenuation and optoelectronic devices.