Holographic efficiency

Fig. 4 Maximum holographic efficiency ri for different spatial fequencies 1/A...

Diffraction gratings may be made by a holographic process, but blaze characteristics cannot be controlled and their efficiency is low in the infrared. They are mostly used for low-order work in the visible and near-ultraviolet. 

Vidal D, Thormann M, Pons M (2005) LINGO, an efficient holographic text based method to calculate biophysical properties and intermolecular similarities. J. Chem. Inf. Model. 45 386-393. 

Photochemical methods for hologram recording are very similar to the ones mentioned above. Excellent holographic parameters were obtained for polydiacetylenes [173, 174]. A diffraction efficiency of up to 40% for a spatial frequency of 1600 mm 1 and with a sensitivity of 5 cm2 J-1 was realized. Such a medium may be used in optical processing. 

The use of a grating to facilitate the out-coupling has been demonstrated [52]. In that work, a (methyl-3 -(p-nitro-phenyl)carbazate, MNCZ) crystal was used as the substrate with a slab transparent waveguide made of photoresist deposited on top. The grating coupler was fabricated holographically and the SHG of a Nd YAG 1.06 pm laser demonstrated. This nonlinear crystal has a nonlinear d36 coefficient of 22.7 pm V-1 (3 time larger than d24 of KTP) and a cut-off wavelength of 455 nm. Reported conversion efficiencies were at that time limited by lack of sufficient crystal flatness. 

At low conversions the diffraction efficiency of the holographic grating can be monitored to determine the rate of photodimerization. Kohler et al. have measured an upper limit on the activation energy for photodimerization of 3.6 kcal/mol, which is very close to a value of about 3.1 kcal/mol determined by Nakanishi et al. for the dimerization of distyrylpyrazine [96]. Rates of disappearance of the diffraction pattern can be used to measure the rate of reversion to starting monomer which occurs upon thermal annealing above 100°C. Kohler et al. have measured the activation energy for this process to be 23.7 kcal/mol. 

Material science can also benefit from oligomeric state of proteins. New retinal nano-ceramic materials with pillared hybrid micro-structures were fabricated for potential applications in optical holographic data storage. It was observed that the Schiff bases in retinal have substantial effect on optical properties of nano-ceramic films as well as diffraction efficiency for holographic storage. This study indicates feasibility of optimizing optical properties of nano-ceramic clay systems using Schiff bases for a variety of photonic applications.40... 

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