Embossed holograms

A nanophotonic hierarchical hologram can be created by adding a nanometric structural change to a conventional embossed hologram. Figure 2.12 shows the basic composition of the hierarchical hologram. 

As shown in Fig. 2,15, we created a sample device to experimentally demonstrate the retrieval of a nanophotonic code within an embossed hologram. The entire device structure, whose size was 15 mm x 20 mm, was fabricated by electron-beam lithography on an Si substrate, followed by sputtering a 50 nm-thick Au layer, as schematically shown in the cross-sectional profile in Fig. 2.15b. 

As shown in Fig. 2.16a, the square-shaped structure was embedded in a periodic one-dimensional wire-grid structure, whose pitch was 150 nm, which models the typical structure of an embossed hologram. As shown in Fig.2.16d, on the other hand, the square-shaped structure, whose size was the same as that in Fig. 2.16a, was not provided with any grid structure. By comparing those two cases, we can evaluate the effect of the environmental structures around the nanophotonic code. Also, we chose the square-shaped structure that is isotropic in both the x and y directions to clearly evaluate the effects of environmental structures and ignore the polarization dependency originating in the structure of the nanophotonic code itself. Periodic-conditioned computational boundaries were located 1.5 im away from the center of the square-shaped structure. The wavelength was set to 785 nm. 

Tate, N., Naruse, M., Yatsui, T., Kawazoe, T., Hoga, M., Ohyagi, Y., Fukuyama, T., Kitamura, M., Ohtsu, M. (2010). Nanophotonic code embedded in embossed hologram for hierarchical information retrieval. Optics Express, Vol. 18, pp. 7497-7505, 2010... 

National Geographic crafted an entire magazine cover made of an embossed hologram in 1988. 

Figure 16.16 Atomic force micrograph of an embossed hologram on thixotropic composite based on Zr02- The surface of the hologram is not a perfect grating because of the superposition of different interference patterns.

Photoresists. These are used in holography because they can be employed to map holographic exposures into surface relief. This property is utilised in the production of embossing masters, reflection and transmission gratings and in computer generated holograms. 

Fig. 5. Schematic diagram of the sample device for demonstration of nanophotonic hierarchical hologram with a nanophotonic code embedded within the embossed structure of Virtuagram .

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