Optical-limiting properties of oleylamine-capped gold nanoparticles for both femtosecond and nanosecond laser pulses.

We report strong broad-band optical-limiting properties of oleylamine-capped gold nanoparticles in solution for both femtosecond and nanosecond laser pulses. The nanosecond optical-limiting effects were characterized by using fluence-dependent transmittance measurements with 7 ns laser pulses at 532 and 1064 nm, and the femtosecond optical-limiting effects were characterized with a z-scan technique using 300 fs laser pulses at 780 nm. The oleylamine-capped gold nanoparticles were found to show strong broad-band optical-limiting effects for nanosecond laser pulses at 532 and 1064 nm and femtosecond laser pulses at 780 nm. These oleylamine-capped gold nanoparticles displayed exceptional optical-limiting effects with thresholds lower than that of carbon nanotube suspension, a benchmark optical limiter. Input-fluence- and angle-dependent scattering measurements suggested that nonlinear scattering played an important role in the observed optical-limiting behavior at 532 and 1064 nm.