On the applicability of the surface impedance integral equation for optical and near infrared copper dipole antennas

The applicability of the surface impedance integral equation (SI-IE) method for the analysis of optical and near-infrared copper dipole antennas is assessed, and some issues relative to resonant half-wavelength optical dipoles are highlighted. Since at these frequencies the conductivity of copper (and of all metals) is relatively small, the appropriateness of using the standard integral equation method for imperfectly conducting wires, based on a surface impedance boundary condition, needs to be examined. Here it is found that the SI-IE method yields accurate results in the near-infrared regime, and for suitably small wire radius values at low optical frequencies. For the middle and upper optical frequencies the approximate SI-IE is not generally valid. Some results are presented for a half-wave dipole resonant in the upper near-infrared/low optical range, and a discussion of the trade-off between maintaining good polarization selectivity and radiation efficiency is provided.