Organic nonlinear optical materials

Organic materials are expected to have relatively strong nonlinear optical properties due to delocalized electrons at  π − π {\displaystyle \pi -\pi } * orbitals. This expectation explains extensive search for better NLO materials among organic crystals.

## L-arginine maleate dihydrate

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L-arginine is one of the essential amino acids widely distributed in biological substances. It forms a number of salts with organic and inorganic acids showing non-linear optical properties. L-Arginine maleate dihydrate (C6H14N4O2,C4H4O4,2H2O) is one of these L-arginine salts which is a complex of strongly basic amino acid, carboxylic acid and provides useful information in relation to molecular interaction in present-day biological systems and to prebiotic self-organisms.[1] It is also a nonlinear optical material with second harmonic generation efficiency 1.68 times that of KDP.[2] L-arginine maleate dihydrate crystals are grown from solution by solvent evaporation; they belong to the triclinic space group P1.

## L-methionine L-methioninium hydrogen maleate

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L-methionine L-methioninium hydrogen maleate also belongs to the amino acid family. Crystals are grown by slow evaporation of an aqueous solution containing L-methionine and maleic acid, resulting in centimeter-large crystals of a non-centrosymmetric space group.[3] They were applied for second-harmonic generation of an Nd:YAG laser (wavelength 1064 nm), and SHG efficiency equal to that of KDP has been obtained.

## References

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1. ^ S.L. Miller, E.L. Orgel, "The Origins of Life on the Earth", Prentice-Hall, New Jersey, 1974.
2. ^ Mallik, Tapati; Kar, Tanusree; Bocelli, Gabriele; Musattib, Amos (March 2005). "Synthesis, crystal structure and solubility of C6H14N4O2,C4H4O4,2H2O". Science and Technology of Advanced Materials. 6 (5): 508–512\. doi:10.1016/j.stam.2005.01.001.
3. ^ Natarajan, Subramanian; Devi, Neelamagam Rajan; Dhas, Sathiya; Dhas, Martin Britto; Athimoolam, Shanmuganarayanan (July 2008). "Crystal growth and structure of L-methionine L-methioninium hydrogen maleate—a new NLO material". Science and Technology of Advanced Materials. 9 (2): 025012. Bibcode:2008STAdM...9b5012N. doi:10.1088/1468-6996/9/2/025012. PMC 5099744. PMID 27877987.