Electro‐optic properties of the organic salt 4‐N,N‐dimethylamino‐4′‐N′‐methyl‐stilbazolium tosylate

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., e1=5.2±0.4. This combination leads to large polarization‐optical coefficients.