Holographic pattern

Fig. 9. Holographic pattern recognition system, (a) Recording an angularly multiplexed hologram (b) forming correlation outputs using arbitrary input...

Figure 6 Cross-section of a switchable grating from photoresist (Strategy 3). By using standard semiconductor fabrication techniques, a cell can be constructed with a holographically patterned central electrode. After filling with LC, the cell can be switched on and off with an electric field applied between the outer unpatterned electrodes.

Two-photon-initiated polymerization (TPIP) can easily produce three-dimensional holographic pattern. The scheme of TPIP is shown in Figure 5.22. Areas encountering double beams of 745 nm (near-infrared laser) are polymerized by two photons. Scanning double beams produce a three-dimensional structure. Kondo et al. reported on a two-photon-initiated polymerization system. A composite of the TPIP is shown in Figure 5.23. 

Birnkrant, M.J. Combining holographic patterning and block copolymer self-assembly to fabricate hierarchical volume gratings. In Material Science and Engineering, Thesis of Drexel University, Philadelphia (2009)... 

Li J, Liang G, Zhu X, Yang S (2012) Exploiting nanoroughness on holographically patterned three-dimensional photonic crystals. Adv Funct Mater 22(14) 2980-2986. doi 10.1002/ adfm.201200013... 

Experimental applications include the direct deposition of patterns as small as 0.5 im in semiconductor applications using holographic methods, and the production of rods and coreless boron and silicon carbide fibers (see Ch. 19). 

Unfortunately, the experimental data cannot be correlated directly with the crystal structure, because some of the information needed is lost in recording the X-ray intensity pattern. Indeed, the diffracted X-ray beam is a vector, and it has both an intensity and a phase angle. The information concerning phase angle is lost during measurement of the X-ray intensity. The phase angle could, perhaps, be recorded by a holographic method, but X-ray lasers do not as yet exist. 

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