Abstract
Intense femtosecond laser irradiation reshapes gold nanorods, resulting in a persistent hole in the optical absorption spectrum of the nanorods at the wavelength of the laser. Single-pulse hole-burning experiments were performed in a mixture of nanorods with a broad absorption around 800 nm with a 35-fs laser with 800 nm wavelength and 6 mJ/pulse. A significant increase in hole burning width at an average fluence of 106 J/m2 has been found, suggesting a tripled damping coefficient of plasmon. This shows that the surface plasmonic effect still occurs at extremely high femtosecond laser fluences just before the nanorods are damaged and the remaining 10% plasmonic enhancement of light is at the fluence of 106 J/m2, which is several orders of magnitude higher than the damage threshold of the gold nanorods. Plasmon–photon interactions may also cause an increase in the damping coefficient.
Highlights
Intense femtosecond laser irradiation reshapes gold nanorods, resulting in a persistent hole in the optical absorption spectrum of the nanorods at the wavelength of the laser
An obvious peak at about 800 nm could be seen, which is the wavelength of the laser, indicating that the nanorods that resonate with the laser wavelength are destroyed the most
It suggests an increase in transverse modes of surface plasmon, which could be found in both nanorods and nanospheres
Summary
Intense femtosecond laser irradiation reshapes gold nanorods, resulting in a persistent hole in the optical absorption spectrum of the nanorods at the wavelength of the laser. A significant increase in hole burning width at an average fluence of 106 J/m2 has been found, suggesting a tripled damping coefficient of plasmon This shows that the surface plasmonic effect still occurs at extremely high femtosecond laser fluences just before the nanorods are damaged and the remaining 10% plasmonic enhancement of light is at the fluence of 106 J/m2, which is several orders of magnitude higher than the damage threshold of the gold nanorods. Gold nanorods attract our attention due to their applications in medicine, chemistry and physics, including biosensing[1], drug delivery[2], cellular imaging[3,4], cancer therapy[5], chemical analysis6,7, catalysts8–12, electronics[13,14] and nonlinear processes[15] These applications utilize the plasmonic effect: the interaction of conductive electrons in the metallic structures with electromagnetic fields[16]. These methods do not provide instantaneous information of Ŵ right before the time that the nanoparticles are melted or damaged when they interact with an intense femtosecond laser pulse
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