Organic Salts with Large Second-Order Optical Nonlinearities
This paper presents a review of recent work on the development of organic salts for second-order nonlinear optical applications. In particular, salts in which the cation has been designed to have a large molecular hyperpolarizability and in which variation of the counterion facilitates preparation of crystals with the required noncentrosymmetric packing are discussed. In many cases, this approach has led to materials with large powder second harmonic generation (SHG) efficiencies. One salt, N,N-dimethylamino-N'-methylstilbazolium p-toluenesulfonate, DAST, exhibited an SHG efficiency >1000 times that of a urea powder reference. A common layered-polar-sheet crystal packing motif was observed for DAST and several salt crystals that have been examined crystallographically. A possible explanation for the high incidence of noncentrosymmetric packing in these structures is discussed. Finally, the growth and properties of DAST single crystals are reviewed.
© 1994 American Chemical Society. Received February 11, 1994. Revised Manuscript Received June 7, 1994. Dedicated to the memory of Margaret Etter. The research described in this paper was performed in part by the Jet Propulsion Laboratory, California Institute of Technology as part of its Center for Space Microelectronics Technology and was supported by the Advanced Research Project Agency and the Ballistic Missile Defense Organization, Innovative Science and Technology Office through an agreement with the National Aeronautics and Space Administration (NASA). C.P.Y. wishes to acknowledge his wife Pamela for permission to work on this paper over the weekend and AFOSR contract F49620-91-C-0075. The authors thank their colleagues: G. Bourhill, E. Boden, O. Ducheneaux, D. Fobare, S. Gilmour, P. Groves, B. Lawrence, W. Lotahaw, K. J. Perry, P. Phelps, E. T. Sleva, K. R. Stewart, and B. Tiemann for technical assistance and many helpful discussions. In particular, we thank Lawrence Henling, Richard Marsh, and William Schaefer for performing the X-ray determinations in this paper. S.R.M. and J.W.P. thank Prof. P. Günter for providing his group's manuscript prior to publication. S.R.M. and J.W.P. also thank Debbie Chester for instantaneous secretarial help.
Supplemental Material - cm00044a012_si_001.pdf