Thermochemical laser writing on transition metal films for the formation of grayscale and diffractive structures

The results of thermochemical laser writing on bi-layer Si/Ti, Si/Zr, Si/Hf films and single-layer Cr film are presented. Silicon capping layer on top of Ti, Zr, Hf metal films protects them from oxidation in atmosphere and increases optical absorption. It has been shown that the thermochemical effect leads to a significant increase in the reflectance in the exposed areas and makes it possible to produce grayscale structures on mentioned-above materials. Bi-layer Si/Ti, Si/Zr, Si/Hf films make it possible to form directly reflective patterns without etching. In addition, there is a significant increase in the optically measured profile depth between the exposed areas and the original bi-layer film. This effect can be used for one-stage technology for direct laser writing of reflective amplitude-phase diffractive structures on these bilayer materials. Writing on Cr film allows to get larger reflection and transmission change but requires etching.