Fabrication and spectral tuning of standing gold infrared antennas using single fs-laser pulses

Upright standing gold monopole nanoantennas are fabricated by irradiation of thin gold films with single pulses of fs-laser radiation. The resulting antennas exhibit extinction resonances in the mid infrared spectral rage for p-polarized light under grazing incidence. Due to the free charge carriers in the surrounding gold film of the antenna, the resonance condition of the thin-wire monopole antenna can be explained by introducing image charges yielding an observable resonance wavelength of four times the antenna length. The antenna length is controlled coarsely by the focusing numerical aperture and fine by the pulse energy of the laser pulse producing the structure. An additional ultrafine tuning of the resonance wavelength with a sub-10 nm resolution is realized by an additional coating process subsequent to the laser structuring.