Application of TCO, indium tin oxide, nanorod arrays for ultrafast switching of light
R. P. H. Chang
Northwestern University, USA
E-mail
All-optical control of plasmons can enable optical switches with high speeds, and high on/off
ratios. We demonstrate ultrafast plasmon modulation in the near-infrared (NIR) to mid-
infrared (MIR) range by intraband pumping of indium tin oxide nanorod arrays (ITO-NRAs).
We observe redshifts of localized surface plasmon resonances arising from a change of the
plasma frequency of ITO, which is governed by the conduction band non-parabolicity. We
generalize the plasma frequency for non-parabolic bands, quantitatively model the fluence-
dependent plasma frequency shifts, and show that different from noble metals, the lower
electron density in ITO enables a remarkable change of electron distributions, yielding a
significant plasma frequency modulation and concomitant large transient bleaches and
induced absorptions, which can be tuned spectrally by tailoring the ITO-NRA geometry. The
low electron heat capacity explains the sub-picosecond kinetics that is much faster than noble
metals. Our work demonstrates a new scheme to control infrared plasmons for optical
switching, telecommunications and sensing.
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