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Title: Nanoplasmonics & opto-electronics
Author: Gusken, Nicholas
ISNI:       0000 0004 9351 0105
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2019
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The ever increasing rates of data transmission around the globe drive conventional electronic computer chips for information processing towards their limits [1, 2]. New concepts are required, capable of providing fast and broadband signal processing while keeping costs and energy consumption at a minimum. Indeed, optical chips constitute a good solution to this problem but suffer from size restrictions as their device features need to be larger than the wavelength of light. Photonic-plasmonic hybrid systems constitute a viable alternative to overcome this obstacle, consisting of low-loss dielectric transmission lines interlinked with compact plasmonic devices capable of communicating with electronic transistors. In these devices, efficient energy conversion from the microscopic optical domain to the nanoscopic electronic domain is key to render next generation computing platforms possible. Hence, this work examines low-loss conversion from the photonic to the plasmonic regime which allows to focus light below its diffraction limit by coupling directly to collectively oscillating electron distributions, called surface plasmons. Here, a Si-compatible nanofocusing platform is investigated, which enables to produce large field intensities in tens of nm3 volumes and allows to direct energy into and out-of sub-wavelength scaled plasmonic waveguides. For the first time, an incoupling efficiency exceeding 80% is demonstrated. Furthermore, efficient nano-de-focusing is successfully exploited for the first time to enhance photoluminescence of Er3+-ion emitters placed in a HGPW geometry. This constitutes a promising approach for room-temperature single-photon emission and on-chip signal processing as Er3+ emits at telecommunications wavelength. Closely related to on-chip signal processing is opto-electronic sensing and light detection. However, solid state sensors are generally bandgap energy limited. Here, we investigate hotcarrier Schottky barrier junctions which work via carrier excitation at a metal/semiconductor interface with sufficient energy to surpass a Schottky barrier (SB) while not being limited by the bandgap. The successful implementation of a self-powered, Si-compatible hotcarrier infrared SB detector is demonstrated. Titanium nitride is used which strongly boost the response, originating in a thin TiO2−x interlayer as demonstrated for the first time.
Supervisor: Oulton, Rupert ; Maier, Stefan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral