A thin layer of ionic crystal is grown on a substrate. The crystal could be any type of ionic crystal, such as sodium chloride or potassium chloride. The crystal is a pure form of the chosen compound and may contain contaminants which would shift the wavelength of created color centers. On top of the first crystal layer, a second thin layer of a different type of crystal is deposited, such as lithium fluoride or sodium fluoride. When these two layers are radiated with gamma rays, they will each form color centers at the spots radiated. Because of the difference in crystalline properties of the two different ionic crystal centers, their color centers would be at different wavelengths. Each of the two separate ionic crystals will emit light at different characteristic wavelengths when illuminated at their unique absorption frequencies. Each layer can be made to lase separately. The top layer has an absorption energy greater than that of the bottom layer, so that the layer energy of the bottom layer absorption peak will pass through the top layer and be absorbed only by the bottom layer. There are many ways of forming F-centers in the two superimposed layers, such as by the use of selective gamma radiation by heating of an anion layer of the particular compound and then depositing the second ionic crystal on the first ionic crystal and then depositing an anion layer on the second crystal and then heating to produce a structure which will lase it to the different frequencies.