Linear and nonlinear optical properties of the organic crystal DSTMS

We report on the linear and nonlinear optical properties of the novel organic crystal $4\text{-}N$, N-dimethylamino-$4^{\prime }\text{-}{N}^{\prime }$-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS). The principal refractive indices $n_1$, $n_2$, and $n_3$ have been determined by a direct measurement of the group index dispersion over a broad wavelength range from $0.6\text{to}1.6\mu \mathrm{m}$. The linear absorption coefficients for light polarized along the dielectric axes have been measured in the transparency range from $600\text{to}2000\mathrm{nm}$. DSTMS crystals show a large birefringence of $\Delta n=0.5$ and low absorption $\alpha <0.7{\mathrm{cm}}^{-1}$ in the telecommunication wavelength range at $1.55\mu \mathrm{m}$. Furthermore, the nonlinear optical tensor elements $d_{111}$, $d_{122}$, and $d_{212}$ have been determined by the Maker-fringe technique at the fundamental wavelength of $1.9\mu \mathrm{m}$. DSTMS crystals exhibit a very large nonlinear activity with a nonlinear optical coefficient $d_{111}=214\pm 20\mathrm{pm}∕\mathrm{V}$. Phase-matching curves determined from our optical data showed that parametric oscillation can be achieved in the wavelength range from $1\text{to}2.2\mu \mathrm{m}$ with effective nonlinear optical coefficients larger than $25\mathrm{pm}∕\mathrm{V}$.