optical properties of plasmonic nanopillars at visible wavelengths

in the present article, we study the optical properties of conical plasmonic nanopillars at visible wavelengths. interestingly, it is shown that two peaks in the optical extinction spectra can be observed for nanopillars with smaller lengths and corner angles. however, by increasing corner angle to 90^◦, two distinct peaks shift, merge together and only a single broad peak is seen in the spectral range. in this special case, the conical nanopillars form the cylindrical nanorods, for which the quasistatic analytical solution of spheroid is used to compare the results.