Observation of Saturable and Reverse Saturable Absorption at Longitudinal Surface Plasmon Resonance in Gold Nanorods

摘要

Saturable and reverse saturable absorption at longitudinal surface plasmonresonance (SPR) in gold nanorods (Au NRs) have been observed using Z-scan andtransient absorption techniques with femtosecond laser pulses. At lowerexcitation irradiances, the wavelength dispersion of saturable absorption hasbeen determined near the longitudinal mode of SPR with a recovery timedetermined to be a few ten picoseconds on the SPR resonance. With higherexcitation irradiances, reverse saturable absorption occurs and becomesdominant. The underlying mechanisms are discussed. Such reversible saturableabsorption makes Au NRs an ideal candidate for optical limiting applications.