Nano-antennas for optoelectronics and nanophotonics

Abstract

The evolution of the design of radio and microwave antennas has allowed new, diverse, and ubiquitous applications of great added value, ranging from global positioning systems to cellular-phone networks. Scaling these designs down towards optical wavelengths has faced two main practical restrictions. On one hand, until recently there have been technological and fabrication issues. On the other, they could not compete against the prevailing semiconductor-based emitters (light-emitting diodes, laser diodes) and detectors (PIN detectors, avalanche photo diodes, etc.). It is now a time of new opportunity for optical or nano-antennas. An optical antenna, also called an antenna-coupled optical detector, is the marriage of two clearly distinguishable elements working conjointly: a metallic antenna structure that collects the optical radiation, and a transducer that turns the received power into an electric signal. Each of these elements can be optimized for a given application. Nano-antennas are the smallest detectors available, scaled to a fraction of the received wavelength. By nature they are direction, wavelength-, and polarization-sensitive elements. The transduction mechanism has a potential response time in the order of tens of femtoseconds. Optical antennas have the advantage that they are integrable with diffractive and conventional optical elements, waveguides, and read-out electronics, and they work at room temperature. A comparison of the performance of these devices with other detectors is shown in Figure 1. Based on this analysis, optical antennas are set to detect light in polarimetric imaging systems, multiband and multispectral applications from the visible to the millimeter-wave bands (see Figure 1. This fractal bow-tie antenna array is designed to detect five bands centered at wavelengths of λ0, 2λ0, 4λ0, 8λ0, and 16λ0.