Synthesis of Benzo[b]naphtho[2′,3′ ∶5,6][1,4]dithiino[2,3-i]thianthrene-5,7,9,14,16,18-hexone and Its Third-order Optical Nonlinearity

Benzo[b]naphtho[2′,3′∶5,6][1,4]dithiino[2,3-i]thianthrene-5,7,9,14,16,18-hexone(4) was synthesized from 1,4-naphthaquinone and the structure was confirmed by 1H NMR and IR. The third-order optical nonlinearity of 4 was measured by using Ti ∶sapphire femtosecond laser(λ=800 nm, ι0=80 fs) and two-beam degenerate four-wave mixing technique. The third-order nonlinear optical susceptibility χ(3), the nonlinear refractive index n2, the second-order hyperpolarizability γ and response time of 4 were was 2.89×10-13 esu, 5.31×10-12 esu, 3.14×10-31 esu and 101 fs, respectively. The influence of the molecular structure of 4 on the third-order optical nonlinearity was analyzed.