Fluidic optical elements and systems use isotopically specified fluids for processing light passing therethrough. The isotopic composition of the fluid may be adjusted to vary the optical properties. The properties of the isotopically specified fluid may be monitored and adjusted to obtain the desired optical characteristics of the fluidic optical element. In one embodiment, a method of optically processing light includes directing light through an optical element that includes an isotopically specified fluid disposed in a confined space. The isotopically specified fluid is selected to provide a preset desired effect on the light directed therethrough for optically processing the light.