With the rise of two-dimensional materials, there has been a need to find techniques which fully harness these materials’ unique properties. One important way to control these materials is via manipulation of their Fermi levels. A novel effect enables all-optical persistent bidirectional control of thin film materials’ Fermi levels when they are placed on a strontium titanate substrate and stimulated with light with energy either above (ultraviolet) or below (red) strontium titanate’s band gap. I present work using this optical gating technique to bidirectionally control the Fermi level of graphene and molybdenum disulfide, and show that this method corresponds to electrical backgating. Furthermore, I present research utilizing Kelvin probe force microscopy to investigate the work function response of bare strontium titanate to ultraviolet illumination, and to show how iron doping and different annealing conditions impact this response. These results demonstrate the applicability of this technique to diverse two-dimensional material systems, and provide new insight into a non-invasive method of Fermi level control which could prove useful for emerging applications.