Research On Optical Limiting Behaviors And Mechanism Of The Broadband Optical Limiter

The optical limiting behaviors and mechanisms of carbon nanotubes suspensions, carbon nanotubes doped in SiO₂ and vanadium oxide thin films were investigated through a series of experiments. The factors affecting the optical limiting were analysed. Based on the nonlinear optics and Mie theory, the optical limiting mechanism of carbon nanotubes was discussed and explained. A preliminary nonlinear scattering physical model of carbon nanotubes was presented to explain the optical limiting. The optical limiting behaviors of vanadium oxide thin films were investigated experimentally and the heat-induced phase transition are also analysed. The main contents of this paper are as follows.1. Optical limiting behaviors of carbon nanotubesMulti-walled carbon nanotubes water-surfactant and ethanol suspensions were prepared by ultrasonication, the optical limiting curves for 1064 run, 10 ns Nd:YAG Q-Switched pulsed laser were measured and the optical limiting behaviors to repetitively pulsed laser was also measured. The effects of suspensions concentration and solvent properties on optical limiting were analysed. Optical limiter of carbon nanotubes doped in SiO₂ was produced and their optical limiting properties were measured. The experimental results indicate that optical limiting properties of carbon nanotubes doped in SiO₂ is inferior to that of the carbon nanotubes in water-surfactant suspensions at the same conditions.2. Nonlinear optical limiting theoryThe possible optical limiting mechanisms of carbon nanotubes suspensions, doped in SiO₂ are analysed based on nonlinear optics and Mie theory, nonlinear absorption (including two-photon absorption, reverse saturable absorption), nonlinear refraction and nonlinear scattering were analysed in this chapter.3. Optical limiting mechanisms of carbon nanotubesOpen aperture and small aperture Z-scan curves were measured by performing Z-scan experiments, we can know that nonlinear scattering play a predominant role and nonlinear refraction is helpful for optical limiting by comparing and analyzing the curves. An integrating sphere was designed to collect all scattered energy to ascertain the nonlinear scattering. In pump-probe time resolved experiments, probe light signal took on strong...