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Keywords:

  • excited-state absorption (ESA);
  • fluorescence;
  • naphthalimide;
  • nonlinear optical (NLO);
  • two-photon absorption (TPA)

Abstract

Four 1,8-naphthalimide hydrazone molecules with different electron-donating groups have been applied in the study of linear and nonlinear optical (NLO) properties. These compounds showed strong green emission in solution. Their NLO properties such as two-photon absorption (TPA) behavior with femtosecond laser pulses ca. 800 nm and excited-state absorption (ESA) behavior with nanosecond laser pulses at 532 nm were investigated. Compound 4 presented the largest two-photon cross section (550 GM) among them due to two factors: the conjugated length of compound 4 is the longest and the electron-donating ability of compound 4 is the strongest. Different from TPA behavior, compound 2 showed the best nonlinear absorption properties at 532 nm and its nonlinear absorption coefficient and third-order nonlinear optical susceptibilities χ(3) were up to 1.41×10−10 MKS and 4.65×10−12 esu, respectively. Through the modification of the structure, the nonlinear optical properties of these compounds at different wavelengths (532 and 800 nm) were well tuned. The great broad-band nonlinear optical properties indicate hydrazones are good candidates for organic nonlinear optical absorption materials.