  Plasmonic detectors have the potential to provide a method of rapid
spectroscopy without the need of moving mirrors or gratings. Previous
measurements have demonstrated frequency tunable detection based on plasmonic
excitations, however these devices were either small area, polarization
dependent and/or required e-beam lithography. We demonstrate that large area
high sensitivity THz plasmonic detection can be achieved using self-assembly
nanosphere lithography. We achieve a submicron feature size grid covering a
detector area of 4 mm^2. The absorbance at the fundamental, third and 5th
harmonics of plasmon resonances are observed. Measurements at 80 K show a large
transmission change of 25%. We also confirmed a magneto plasmon dispersion of
this device. In this paper we will discuss the frequency dependence of the
radiative damping effect which affects enhanced absorption at the higher
harmonics mode relative to fundamental.
