Abstract

Since their discovery in 1991¹, carbon nanotubes have been the object of optical studies. They exhibit good optical limiting performances for a range of wavelengths broader than fullerenes C₆₀ and carbon black suspensions² (from 400 nm to 1100 nm). We have evidenced a strong nonlinear scattering due to heat transfer from particles to solvent leading to vapour bubble growth around the particles³, but we have also observed a phase change of carbon nanotubes which induces optical limiting behaviour for pulse duration of about 5 ns. For longer pulses (100 ns), we observe two different regimes: the first one corresponds to bubble growth contribution and the second is due to the phase change of carbon nanotubes. To study the optical limiting performances as a function of the pulse duration, we have carried out nonlinear transmittance with f/30 focusing geometry for different pulse durations and wavelengths. These experiments are realized with single wall carbon nanotubes suspended in chloroform and in water. For long pulse durations, the optical limiting behaviour is very promising and we have reduced the optical limiting threshold by more than an order of magnitude. Figure 1 illustrates optical limiting performances for two pulse durations.

© 2000 IEEE