Tuning Second-Order Nonlinear Optical Properties of Cross-Linked Carbon Nanotube via External Electric Field

Many interesting multifunctional materials are obtained under the application of an external electric field, which arouses extensive interest of experimental and theoretical researchers. In the present work, the structure-property relationships of a cross-linked single-walled carbon nanotube (CL-SWCNT) with bisaromatic amine, upper CNT(3, 3), and lower CNT(3, 3) are investigated under a longitudinal external electric field (F). The results show that the effect of the external electric field induces an intramolecular charge transfer (CT) from the lower CNT(3, 3) to the upper CNT(3, 3), which can bring extraordinary first hyperpolarizabilities (beta(tot)). Upon increasing F, the beta(tot) tot values are increased obviously. Significantly, the largest beta(tot) value of 4.55 x 10(4) au is present at F = 50 x 10(-4) au. Moreover, the beta(z) components for the CL-SWCNT are dominant that contribute greatly to the beta(tot) values compared to other components, which is mainly attributed to the intramolecular CT transition. The current work shows that the external electric field appears as a promising strategy for enhancing the nonlinear optical properties and motivates further efforts in the development of carbon nanotubes.