Abstract

Subject of study. In this study, methods for the topology formation of elements based on laser-induced periodic surface structures for implementing various visual effects and structural features in a security hologram recorded directly on the surface of AISI 430 stainless steel are investigated. Purpose of work. The process of recording images based on laser-induced periodic surface structures on bulk metals for creating dynamic images is optimized to solve problems in security holography. Method. The method is based on the formation of laser-induced periodic surface structures under the action of scanning laser radiation with simultaneous rotation of the polarization of laser radiation. The recording process is implemented using nanosecond fiber laser radiation with a wavelength of 1.064 µm in a two-dimensional scanning system with a flat field objective. Main results. A technique is developed for creating a protective hologram comprising a set of laser prints filled with diffractive microgratings with different spatial orientations. The radiation polarization and beam scanning trajectory are the main factors influencing the laser-induced periodic surface structures’ spatial orientation during the formation of structures with a given topology and observed visual dynamic effects based on elementary diffractive microgratings. The period of microdiffraction gratings is equal to the wavelength of the acting laser radiation and approximately 1 µm. Practical significance. The proposed method for the elementary diffractive micrograting formation facilitates the generation of holographic elements/images with different spatial topologies, including various visual and structural features that meet the requirements for modern security holograms in their main application areas.

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