Electrically driven optical antennas and subwavelength slot waveguides [electronic resource]
Keywords: Electrical Engineering.

Computer servers today consume more than 2.5% of the total electricity in the U.S., and the figure is growing at an increasingly faster rate. Furthermore, it has been estimated that 30% of the computer chip power is dissipated in the interconnects, i.e. on information transport alone. The efficiency of the current electrical interconnect technology is unlikely to improve much further, due to the fundamental limits of the achievable metal wire dimensions and the signaling speed requirements. For these reasons, a great deal of effort now focuses on developing an entirely new interconnect technology based on signaling with optical energy, which promises to dramatically decrease energy consumption and enable signaling speeds in the hundreds or thousands of GHz. The most recent developments in high-speed optical interconnection set stringent limits on the power consumption, operating speed, and physical footprint of the constituent active devices. In order to achieve new performance targets, it becomes particularly important to scale down optical sources to the nanoscale. This effort is inhibited by the fundamental diffraction limit of light, where the size reduction of photonic elements dramatically increases optical losses, thereby reducing the interaction strength of optoelectronic processes. Metallic nanostructures which support coupled electron and electromagnetic wave oscillations called surface plasmon polaritons facilitate stronger light-matter interaction at the nanoscale as they are capable of concentrating and confining light to deep sub-wavelength volumes. These plasmonic structures enable significant modification of the electromagnetic environment, allowing nearby optical emission processes to be enhanced and controlled. In this work, I start by describing a theoretical framework for quantifying and visualizing the interaction between a quantum emitter and a nearby plasmonic antenna. This method enables the detailed analysis of the power emitted by the source, the power captured by the antenna, and the power reradiated by the antenna. Understanding the behavior of each of these processes is crucial in developing controllable and tailored sources of light. In the second example, I illustrate the design methodology and demonstrate experimentally, compact antenna-electrodes which facilitate simultaneous operation as electrodes for current injection into nanoscale-LEDs and as antennas capable of optically manipulating the electroluminescence. Different designs of the antenna electrode dimensions show dipolar, quadrupolar and higher order radiation patterns with enhanced directivity and polarization ratio which are in good agreement with full-field numerical simulations. In the final example, I demonstrate the integration of a metal-clad nano-LED with metal-dielectric-metal slot waveguides to realize the smallest electrically-driven two-dimensionally confined guided optical mode to date. The routing, splitting, free space coupling and directional coupling of the subwavelength slot waveguide mode are characterized to enable future optical nano-circuits for high speed optical interconnects and sensing in nanoscale volumes.