Three-dimensional hologram printing by single beam femtosecond laser direct writing

Abstract

This article demonstrates three-dimensional (3D) hologram printing in polymethyl methacrylate (PMMA) and linthum niobate (LiNbO3) samples by means of single beam femtosecond laser direct writing technique. We have printed double-layer 3D hologram, having a background and foreground layer, inside PMMA substrate. Triple-layer 3D hologram, comprising a background, middle, and foreground layer, has been fabricated inside LiNbO3 sample. In both cases, each layer is superimposed over the bottom layers of the holograms. The 3D holograms consist of images (in our case, letters) printed in multiple layers so that each layer is alternately visible depending upon the angle of perspective of the observer. Initially, the target image is converted to an equivalent image by a set of periodic micro-metric lines. Afterwards, using femtosecond laser irradiation a set of periodic diffraction gratings have been fabricated in lieu of micro-lines to form the images in multiple layers, where the orientation of the diffraction gratings is different in different layers. As a result, the 3D holograms display a distinctive multi-color effect.