Dielectric leaky-wave nanoantennas for highly directional emission of light

An important source of innovation in nanophotonics is the idea to scale down known radio wavetechnologies to the optical regime. One thoroughly investigated example of this approach are metallic nanoantennas which employ... [ view full abstract ]

An important source of innovation in nanophotonics is the idea to scale down known radio wavetechnologies to the optical regime. One thoroughly investigated example of this approach are metallic nanoantennas which employ plasmonic resonances to couple localizedemitters to selected far-field modes. While metals can be treated as perfect conductors in the microwave regime, their response becomes Drude-like atoptical frequencies. Thus, plasmonic nanoantennas are inherently lossy.Moreover, their resonant nature requires precise control of the antennageometry. A promising way to circumvent these problems is the use of broadbandnanoantennas made from low-loss dielectric materials.

On the basis on theoretical considerations and numerical simulations we discovered a design rule for broadband dielectric optical leakywaveguide antennas being very robust to fabrication tolerances and showing high directional emission for a wide choice of material combinations.

Here, we report on the theoretical modelling and experimental realization of dielectric leaky-wavenanoantennas made of Hafnium dioxide nanostructures deposited on a glass substrate with high directional light emission. Colloidal semiconductor quantum dots deposited in the nanoantenna feed gap serve as a local light source. The emission patterns of hybrid nanoantennas with different sizes are measured by Fourier imaging and agree very well with our simulations. We find for allantenna sizes a highly directional emission, underlining the broadband operation of our design.

[1] M. Peter, A. Hildebrandt, C. Schlickriede, K. Gharib, T. Zentgraf, J. Förstner, and S. Linden, „Directional Emission from Dielectric Leaky-Wave Nanoantennas“, Nano Letters 7, 4178 (2017).