Controlling the Coupling Strengths in Nanophotonic Networks using Modified Yagi-Uda Nanoplasmonic Antennas

Abstract

On-chip communication in optical neural networks is commonly done via waveguides which results in large system footprints. A compact alternative is to broadcast light signals between nano-optoelectronic components in free space and tailor the light field distribution using sub-wavelength nanophotonics. We propose and simulate nanoplasmonic metal structures in combination with III-V nanowire emitters and receivers to create an optical network in which the shape and position of these nanostructures create varying weights between the nano-optoelectronic nodes. Using Finite Difference Time Domain modelling, we investigate systems of experimentally verified nanowire optoelectronics combined with nanoplasmonic structures that can be made in the same fabrication step as electrical contacts powering the nanowires. We investigate both individual nanowire/antenna devices as well as networks corresponding to two layers in a neural network. We show that directed communication from a nanowire node can be significantly altered using Yagi-Uda antennas. Modifying the antenna with an asymmetric director component enables the directing of light several different angular directions simultaneously. We find that highly variable complex weight distribution between the connections in two seven node layers can be achieved depending on the combined geometry of the antenna components. The possible weight distributions in compact layers of nanowire nodes could be used for creating a variety of neural networks with complex connectivity. The concepts can be generalized to other types of nanoscale emitter/receiver systems.