Nonlinear absorption and nonlinear refraction in a chemical vapor deposition-grown, ultrathin hexagonal boron nitride film

Abstract

An ultrathin hexagonal boron nitride film is synthesized by a method of chemical vapor deposition. Irradiated by femtosecond laser pulses in the visible spectrum of 400-800 nm, it exhibits multiphoton absorption and positive nonlinear refraction properties. The two-photon and three-photon absorption coefficients are of the order of 10^-5 cm W^-1 and 10^-14 cm³ W^-2, respectively. The nonlinear refraction coefficient is as large as ∼10^-8 cm² W^-1. These nonlinear coefficients lead to figures of merit that meet the material requirements for all-optical switching devices.