Date of Award
Doctor of Philosophy (PhD)
Dentcho A. Genov
This dissertation explores the fundamentals of light-matter interaction towards applications in the field of Opto-electronic and plasmonic devices. In its core, this dissertation attempts and succeeds in the the modeling of light-matter interactions, which is of high importance for better understanding the rich physics underlying the dynamics of electromagnetic field interactions with charged particles. Here, we have developed a self-consistent multi-physics model of electromagnetism, semiconductor physics and thermal effects which can be readily applied to the field of plasmotronics and Selective Laser Melting (SLM). Plasmotronics; a sub-field of photonics has experienced a renaissance in recent years by providing a large variety of new physical effects and applications. Most importantly, plasmotronics promises devices with ultra-small footprints and ultrafast operating speeds with lower energy consumption compared to conventional electronics. One of the primary objectives of this dissertation is to present an optoelectronic switch termed as Surface Plasmon Polariton Diode (SPPD) for functional plasmonic circuits based on active control of Surface Plasmon Polaritons (SPPs) at degenerate PN+-junction interfaces.
In this context, the operational characteristics of the proposed plasmonic device are studied by the self-consistent multi-physics model that couples the electromagnetic, thermal and IV characteristics of the device. The SPPD uses heavily doped PN+-junction where SPPs propagate at the interface between N and P-doped layer and can be switched by an external voltage. Here, we explore the features of SPPD using three different semiconductor materials; GaAs, Silicon and Indium Gallium Arsenide (In0.53Ga0.47As). When compared to Si and GaAs, the In0.53Ga0.47As provides higher optical confinement, reduced system size and faster operation. For this reason, in our dissertation (In0.53Ga0.47As) is identified as the best semiconductor material for the practical implementation of the optoelectronic switch providing high optical confinement, reduced system size, and fast operation. The optimal device is shown to operate at signal modulation surpassing -100 dB and switching rates up to 50 GHz, thus potentially providing a new pathway toward bridging the gap between electronic and photonic devices. Also, the proposed optoelectronic switch is compatible with the current CMOS semiconductor fabrication techniques and could lead to nanoscale semiconductor-based optoelectronics.
Furthermore, we have extended the concept of the above optoelectronic switch to design and study a new type of all-optical switch, referred to as Surface Plasmon Polariton Diode (thermal) (SPPDt). The SPPDt operation is governed by a unique optical nonlinearity that exists only for surface electromagnetic waves, i.e. SPPs, propagating at highly doped semiconductor junction interfaces. This dissertation will address the design and characterization of the SPPDt and will bring new insights into the underlying thermo optic nonlinearity. The gained understanding will be applied to design practically feasible devices including logic gates which can bridge the temporal and spatial gap between electronics and optics by providing high switching rates and signal input/output (I/O) power modulation.
Enhanced light-matter interactions have further been explored and extended towards tailoring plasmonic resonances due to laser interactions with metal powder beds pertaining to Selective Laser Melting (SLM) processes. This is done by adapting the self consistent model developed for the plasmonic device to better understand the complex electrodynamic and thermodynamic processes involved in SLM. The SLM is an advanced rapid prototyping or additive manufacturing technology that uses high power density laser to fabricate metal/alloy components with minimal geometric constraints. The fabrication process is multi-physics in nature and its study requires the development of complex simulation tools. In this dissertation, for the first time, the electromagnetic interactions with dense powder beds are investigated under full-wave formalism. Localized gap and surface plasmon polariton resonance effects are identified as possible mechanisms toward improved absorption in small and medium-size titanium powder beds. Furthermore, observed near homogeneous temperature distributions across the metal powders indicates fast thermalization processes and allows for the development of simple analytical models to describe the dynamic interplay of laser facilitated Joule heating and effects of radiation and thermal conduction. The Explicit description is provided for important SLM process parameters such as critical laser power density, saturation temperature, and time to melt. Specific guidelines are presented for improved energy efficiency and optimization of the SLM process deposition rates.
Vinnakota, Raj Kumar, "" (2018). Dissertation. 15.