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Scattering and Extinction Torques: How Plasmon Resonances Affect the Orientation Behavior of a Nanorod in Linearly Polarized Light
journal contribution
posted on 2016-01-07, 20:49 authored by Xiaohao Xu, Chang Cheng, Yao Zhang, Hongxiang Lei, Baojun LiLinearly polarized light can exert
an orienting torque on plasmonic
nanorods. The torque direction has generally been considered to change
when the light wavelength passes through a plasmon longitudinal resonance.
Here, we use the Maxwell stress tensor to evaluate this torque in
general terms. According to distinct light–matter interaction
processes, the total torque is decomposed into scattering and extinction
torques. The scattering torque tends to orient plasmonic nanorods
parallel to the light polarization, independent of the choice of light
wavelength. The direction of the extinction torque is not only closely
tied to the excitation of plasmon resonance but also depends on the
specific plasmon mode around which the light wavelength is tuned.
Our findings show that the conventional wisdom that simply associates
the total torque with the plasmon longitudinal resonances needs to
be replaced with an understanding based on the different torque components
and the details of spectral distribution.