Gold and silver coated carbon nanotubes: An improved broad-band optical limiter

5-nm-thick coatings of polycrystalline gold and polycrystalline silver were deposited on multiwalled carbon nanotubes. Their optical limiting properties were studied as a suspension in water at 532 and 1064 nm wavelengths by nanosecond laser pulses. Experiments show that they possess stronger OL performance compared to pure carbon nanotubes at 532 nm, but there were no visible OL enhancements at 1064 nm. We propose surface plasma absorption of Au and Ag as the mechanism responsible for the enhancement of nonlinear scattering effects. Our study provides evidence that coating carbon nanotubes with polycrystalline Au or Ag is a simple and effective method for improving OL performance.