Third-order nonlinear optical property of poly(2,5-dihexyloxy)- p-phenylene vinylene modified by N + ion implantation

Abstract

A soluble poly(2,5-dihexyloxy)- p-phenylene vinylene (PDHOPV) was prepared via dehydrochlorination reaction from hydroquinone and n-hexyl bromide as raw materials. The PDHOPV films implanted by 20 keV nitrogen ions (N +) in the dose range of 3.8 × 10 15–9.6 × 10 16 ions/cm 2 were characterized by UV–vis absorption spectra, which showed the optical absorption was raised gradually in the visible region followed by a red shift of optical absorption threshold and the band gap ( E g) was reduced from 2.12 eV to 1.71 eV with the increase of ion dose. The third-order nonlinear optical (NLO) susceptibilities ( χ (3)) were measured by degenerate four-wave mixing (DFWM) technique at 532 nm. The results demonstrated that the χ (3) value of PDHOPV film could be enhanced effectively by means of N + ion implantation. When the ion dose was 3.8 × 10 16 ions/cm 2, the χ (3) value of PDHOPV film was maximized to 1.06 × 10 −8 esu which was almost eleven times larger than that of the pristine film. Moreover, the mechanism responsible for the variation of χ (3) value of PDHOPV film with N + ion dose was also discussed tentatively.