A method of fiber core material band gap engineering for artificially modifying fiber material properties is provided. The method includes doping the fiber core material with one or more atoms for enhancing photosensitivity to the fiber material. The method also includes co-doping the fiber core material with one or more ions for enhancing an amorphous network crosslink mean coordination number. The method further includes thermally annealing the fiber core material for widening the band gap of the fiber core material.