Organic nonlinear optical crystal DAST growth and its device applications

The organic ionic salt 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DA ST) is known for its huge nonlinearity among nonlinear crystals, and has ad vantages such as low dielectric constants. This nonlinearity of DAST is bas ed on the large hyperpolarizabilities beta, and it causes large electro-opt ical (E-O) coefficients and nonlinear optical coefficients. With low dielec tric constants to the high-speed devices, the large E-O coefficients genera te the highly efficient E-O modulation and detection in the high-frequency region. In this paper, we report the development of the crystal growth stab ility and reproducibility for large and high-quality DAST by the seed cryst als fixing method. In this method, large enough and crack-free crystals are grown reproducibly with reasonable growth speed. By improved cutting and p olishing processes of DAST crystals, we were able to make samples for devic e applications. With these samples, we demonstrate 60 GHz millimeter wave-f ield monitoring via the large and high-speed E-O effect of DAST. This monit oring system is attractive for applications to ultra-high-speed E-O devices , such as microwave photonics. (C) 1999 Elsevier Science B.V. All rights re served.