We show that the organic salt 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) is a very interesting material for electro-optic applications in the near infrared. The electro-optic coefficients, namely r111, r221, r331, r113, r223, and r333, were determined in the spectral range of 700 up to 1535 nm using optical samples cut from large high quality bulk crystals. DAST combines large electro-optic coefficients, e.g., r111=77±8 pm/V at λ=800 nm and r111=47±8 pm/V at λ=1535 nm, with low dielectric constants, e.g., ε1=5.2±0.4. This combination leads to large polarization-optical coefficients.

Compared to 2-pill therapy, a FDC resulted in important increases in patient adherence. Economic analyses are warranted to determine whether the clinical benefits attributable to the adherence gains are worth the incremental cost of a FDC.

Organic materials with large second-order nonlinear optical (NLO) susceptibilities are of interest because of their potential applications in optical signal processing and frequency conversion.['-31 Much work has therefore been devoted to the search for optimal molecular crystalline materials composed of stable chromophoric molecules with large molecular hyperpolarizabilities with an optimized orientation for large macroscopic NLO effects.Crystal growth research is of basic importance for the application of organic crystals in NLO and electro-optical devices.I4] Bulk crystalline samples of reasonable size and good quality are also essential for the accurate measurement of electro-optical and NLO coefficients in order to evaluate the potential for future applications. In addition, it has been found that, particularly in organic materials, the linear electro-optical responses are strongly dependent on the crystal quality.[" Furthermore, growth of bulk crystals of organic salts with large chromophoric cations has hardly been reported in the literature. In this work, we describe the growth of the organic salt crystal 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST), and the main results of the linear, nonlinear, and electro-optical characterization.In this crystal, the stilbazolium, one of the most efficient NLO chromophores, is the nonlinear optically active part.[61 The anion (tosylate) induces the non-centrosymmetric macroscopic crystal packing (see Fig. 2, bottom). DAST crystals have already been reported to have very large nonlinear optical su~ceptibilities.[~-~~~ The lack of reasonably large and optically homogeneous DAST crystals has hindered the accurate linear, nonlinear, and electro-optical characterization in earlier investigations of DAST.[*-'O1 DAST was synthesized by the condensation of 4-methyl-N-methyl pyridinium tosylate, which was prepared from 4-picoline and methyl toluenesulphonate, and 4-N,N-dimethylamino-benzaldehyde in the presence of pipendine (Scheme 1).DAST was then purified ( > 99.8 %) by recrystallization from water and methanol. Orange co-crystals, DAST . H20, in space group Pi (point group i, z = 2)[l2]were obtained from water or a methanol-water mixture. DAST can hardly be dissolved in non-polar and most polar solvents. Alcohol, however, is a reasonably good solvent for DAST and we found that methanol was the most suitable solvent for the growth of high-quality DAST crystals. The solubility curve for DAST in a methanol solution (see Fig. 1) was defined by saturating solutions at a high temperature and slowly cooling the solution in the presence of a precipitated solid to maintain equilibrium and analyzing the solution at defined temperatures.DAST single crystals were grown from a seeded saturated methanol solution (between 40 and 50°C with concentrations of about 4-5.5 g(DAST)/IOO g(so1vent)) by a 8 . 0 ) . I . , . , . , . , . , .

We report the use of the organic crystal DAST as a freely propagating electromagnetic-wave sensor at terahertz (THz) frequency. We also report the result of using a DAST crystal as a mid-IR THz emitter. Compared with the optical rectification from our best ZnTe emitter, that obtained by use of DAST demonstrates a sixfold enhancement of radiation at 7-20 THz.

We show that the organic salt 4-N,N-dimethylamino-4Ј-NЈ-methyl-stilbazolium tosylate, originally developed for electro-optic applications, is also a very interesting material for phase-matched parametric interactions such as frequency-doubling and optic parametric oscillation in the near infrared. These favorable properties are due to the large off-diagonal element d 26 which gives measured effective phase-matchable nonlinear optical coefficients of d eff ϭ31Ϯ5 and 15Ϯ3 pm/V at the telecommunication wavelengths of ϭ1313 and 1535 nm, respectively.