Ph.D Thesis

Ph.D StudentSorias Ofir
SubjectManipulation of Light Matter Interactions in Nano-Devices
using Plasmonics
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Meir Orenstein
Full Thesis textFull thesis text - English Version


The fundamental physical properties of light-matter interactions that are mediated via optical nanoantennas and nano-structures in general have attracted immense interest in recent years. It is well known that light can strongly interact with metallic particles, and the study of the coupling between light and nano-particles, which can be much smaller than the excitation field wavelength, has advanced and matured in recent decades with the improvement of fabrication and analysis capabilities.

The fields of localized plasmons and optical antennas have emerged, and researchers have developed and studied their applications. Optical antennas can enhance the coupling between free propagating optical electromagnetic field and localized field modes with localized energy, which can significantly increase the interactions between adjacent matter and the optical field. Appropriate design of such optical antennas and their coupling to devices can enhance the device performance and provide control over many of its properties.

This research examines both optical antennas and nanostructure properties and demonstrates the use of such structures to control, enhance, and improve devices. Moreover, it presents a new type of optical active antenna device, namely the Nanoflag antenna, which has many advantages compared to plasmonic antennas. For each of the presented studies, this work details the entire path from theory and conceptualization to simulation and fabrication and, finally, measurements and analysis.

In this thesis, we demonstrate the properties of plasmonic antennas and illustrate means of controlling its resonance, polarization, directionality, and near-field behavior. We utilize these type of nanoantennas to enhance emission from nano-emitters in the form of NWs, nitrogen-vacancy (NV) centers emitting from diamonds, a quantum-well light-emitting device, and more.

We also present improvements to detectors by discussing the largest demonstrated broadband responsivity enhancement to a superconducting NW single-photon detector along with the controllability of its polarization response. We also investigate the gallium nitride quantum cascade detector by experimentally demonstrating responsivity enhancement of more than one order of magnitude as well as other interesting phenomena of Rabi oscillations and strong coupling. We further reveal and explain improvements to a solar-cell and in metal-insulator-semiconductor photodetector through the use of plasmonics. In addition, the fabrication and measurements of a non-adiabatic horn antenna on top of a semiconductor photodetector were also successful and proved to increase its sensitivity and responsivity.

Beyond the above-mentioned metallic nano-structures, we also present an epitaxially grown indium-phosphide Nanoflag as an optically active nano-structure that encapsulates the desired characteristics of a photonic emitter/detector and an efficient epitaxial nanoantenna. By merging active nano-emitters with nanoantennas at a single growth process, we introduce and illustrate a new class of devices for use in nanophotonics applications.

We fully characterize the optical properties of the Nanoflag optical antenna, including its polarization and directionality, and develop the design rules for controlling it. Furthermore, we study its field enhancement and its superior operation as a source or a detector. Ultimately, we experimentally demonstrate an enhanced, morphology-dependent, nonlinear processes of two-photon absorption and second-harmonic generation from the Nanoflag.