Optical properties and interparticle coupling of plasmonic bowtie nanoantennas on a semiconducting substrate

We present the simulation, fabrication, and optical characterization of plasmonic gold bowtie nanoantennas on a semiconducting GaAs substrate as geometrical parameters such as size, feed gap, height, and polarization of the incident light are varied. The surface-plasmon resonance was probed using white light reflectivity on an array of nominally identical, 35-nm-thick gold antennas. To elucidate the influence of the semiconducting, high-refractive- index substrate, all experiments were compared using nominally identical structures on glass. Besides a linear shift of the surface-plasmon resonance from 1.08 to 1.58 eV when decreasing the triangle size from 170 to 100 nm on GaAs, we observed a global redshift by 0.25 ± 0.05 eV with respect to nominally identical structures on glass. By performing polarization-resolved measurements and comparing results with finite-difference time-domain simulations, we determined the near-field coupling between the two triangles composing the bowtie antenna to be ∼8 times stronger when the antenna is on a glass substrate compared to when it is on a GaAs substrate. The results obtained have strong relevance for the integration of lithographically defined plasmonic nanoantennas on semiconducting substrates and therefore for the development of novel optically active plasmonic-semiconducting nanostructures.