Optical properties of phosphorene are tuned by adsorption of alkali metals (Li and Na) and halogens (Br and Cl). It has been found that on increasing the size of alkali metals and halogen adsorbed phosphorene layer the absorption coefficient reduces and shifts towards visible region. The refractive index in alkali metal adsorbed phosphorene increases with size of phosphorene layer. For halogen adsorbed structure it decreases with increase in size of phosphorene layer. Optical absorption is observed to depend on both dielectric constant and refractive index. Since adsorption of alkali and halogen materials modifies the refractive index of phosphorene, absorption is seen to reduce in all cases where refractive index increases due to adsorption even when the dielectric constant was high.
