Nonlinear optical and optical limiting properties of ultra-long gold nanowires

• Ultra-long gold nanowires (NWs) were prepared and characterized.
• The gold NWs were largely constructed from gold nanorods.
• OL effect of Ultra-long gold NWs is superior to that of CNTs.
• Increasing excitation energy leads to transformation from SA to RSA in Au NWs.
• NLS played an important role in the OL activity of the ultra-long gold NWs.

Ultra-long gold nanowires (NWs) were prepared and characterized. The gold NWs were predominantly formed from gold nanorods. The ultraviolet–visible absorption spectrum of the gold NWs contained two absorption bands. One corresponded to transverse surface plasmon absorption in the gold NWs, and the other to absorption by residual organic groups. The nonlinear optical and optical limiting (OL) properties of the gold NWs were characterized by the open aperture Z-scan technique, using 532-nm laser pulses with pulse duration of ~7 ns. The NWs exhibited strong OL effects for nanosecond laser pulses at 532 nm, and their OL performance was superior to that of carbon nanotubes; a benchmark OL material. Thus, the gold NWs could potentially replace carbon nanotubes in OL applications. Nonlinear scattering played an important role in the OL activity of the ultra-long gold NWs at 532 nm. The nonlinear behavior of the gold NWs altered from saturable absorption to reverse saturable absorption, with increasing excitation energy. This property can be exploited in optical pulse compressors, optical switching, and laser pulse narrowing.