Ultrafast Modulation of the Plasma Frequency of Vertically Aligned Indium Tin Oxide Rods

DANIEL B. TICE; SHI-QIANG LI; MARIO TAGLIAZUCCHI; D. BRUCE BUCHHOLZ; EMILY A. WEISS; ROBERT P. H. CHANG

NANO LETTERS (PRINT)

AMER CHEMICAL SOC

Lugar: Washington; Año: 2014 vol. 14 p. 1120 - 1126

1530-6984

Light−matter interaction at the nanoscale is of particular interest for future photonic integrated circuits and devices with applications ranging from communication to sensing and imaging. In this Letter a combination of transient absorption (TA) and the use of third harmonic generation as a probe (THG-probe) has been adopted to investigate the response of the localized surface plasmon resonances (LSPRs) of vertically aligned indium tin oxide rods (ITORs) upon ultraviolet light(UV) excitation. TA experiments, which are sensitive to the extinction of the LSPR, show afluence-dependent increase in the frequency and intensity of the LSPR. The THG-probe experiments show a fluence-dependent decrease of the LSPR-enhanced local electric field intensity within the rod, consistent with a shift of the LSPR to higher frequency. The kinetics from both TAand THG-probe experiments are found to be independent of thefluence of the pump. These results indicate that UV excitation modulates the plasma frequency of ITO on the ultrafast time scale by the injection of electrons into, and their subsequent decay from, the conduction band of the rods. Increases to the electron concentration in the conduction band of∼13% were achieved inthese experiments. Computer simulation and modeling have been used throughout the investigation to guide the design of the experiments and to map the electricfield distribution around the rods for interpreting far-field measurement results