Synthesis and features of nonlinear optical switches based on dithienylethene unit

Abstract

Two nonlinear optical (NLO) chromophores C1 and C2 based on dithienylethene were designed and synthesized as the ultraviolet NLO switches. The open/close behavior of C1 and C2 were investigated through the UV–vis spectra. Through quantum chemical calculations of the dipole moments, first and second hyperpolarizabilities, etc. we analyzed both opening and closure states of C1 and C2. The NLO switch ability of the chromophores were studied through monitoring of the SHG at the opening/closure states, which were performed under illumination of fourth harmonic generation of the nanosecond Nd:YAG laser (λ = 266 nm). The obtained results indicated that the maximal SHG changes were observed at energy density equal to about 90 J/m2, and the samples C1, 2′ closure states possess significantly higher value of the second order susceptibility compared to the opening states. After switching off of the external UV light, the induced second order susceptibilities remain up to 150 h without a decrease, which indicated that the obtained chromophores have the potential application as the NLO switches applied in photonics.