Fabrication of mid-infrared plasmonic antennas based on heavily doped germanium thin films

In this work, the growth and the fabrication of heavily doped germanium plasmonic antennas for mid-infrared applications are reported. By tuning the phosphorus doping concentration and the antenna geometrical parameters, plasma frequencies for targeting the 8-15 mu m spectral region are achieved. 1 mu m thick, heavily doped (2.3 x 10(19) cm(-3)) germanium was used to fabricate dipole antennas of 800 nm width with a gap spacing of 300 nm which demonstrate resonance frequencies around 13 mu m and 13.5 mu m for 2 mu m and 3 mu m long structures, respectively. This technology has the potential to be used for mid-infrared sensing applications of hazardous gases and liquids. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.