The content of this thesis encompasses the fundamentals, modelling, chip design, nanofabrication process, measurement setup, and experimental results of devices exploiting the optical properties of phase-change chalcogenide materials. Special attention is paid to integrated Si<sub>3</sub>N<sub>4</sub> nanophotonic circuits for optical switching and memory applications, as well as to multilayer stacks for colour modulation. Herein, the implementation of the first robust, non-volatile, phase-change photonic memory is presented. By utilising optical near-field effects for Read, Write and Erase operations, bit storage of up to eight transmission levels is demonstrated in a single device employing Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> as the active material. These on-chip memory cells feature single-shot read-out of the transmission state and switching energies as low as 13.4pJ at speeds approaching 1GHz. The capability to readily switch between intermediate states is also demonstrated, a feature that requires complex iteration-based algorithms in electronic phase-change memories. This photonic memory is not only the first truly non-volatile memory---a long-term elusive goal in integrated photonics---but could also potentially represent the first multi-level memory, including electronic counterparts, that requires no computational post-processing or drift correction. These findings provide a pathway towards solving the throughput limitations of current computer architectures by eliminating the so-called von-Neumann bottleneck and portend a new paradigm in all-photonic memory, non-conventional computing, and tunable photonic devices. Finally, novel capabilities in electro-optic colour modulation using phase-change materials are demonstrated. In particular, this thesis offers the first implementation of Ag<sub>3</sub>In<sub>4</sub>Sb<sub>76</sub>Te<sub>17</sub>-based optical cavities for colour modulation on low-dimensional multilayer stacks. Moreover, "gray-scale" image writing is demonstrated by establishing intermediate levels of crystallisation via voltage modulation. This finding, in turn, corresponds to the first demonstration of nonvolatile colour-depth modulation in the emerging phase-change materials nanodisplay technology, featuring resolutions down to 50nm. Furthermore, a comprehensive comparison is carried out for two types of materials: growth- (Ag<sub>3</sub>In<sub>4</sub>Sb<sub>76</sub>Te<sub>17</sub>) and nucleation-dominated (Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub>) alloys in terms of colour, energy efficiency, and resolution. These results provide new tools for the new generation of bistable and ultra-high-resolution displays and smart glasses while allowing for other potential applications in photonics and optoelectronics.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:730435 |
| Date | January 2016 |
| Creators | Ocampo, Carlos Andrés Ríos |
| Contributors | Bhaskaran, Harish |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ora.ox.ac.uk/objects/uuid:1c2c3179-ef9f-4fbf-b91c-c4d2f7ee7ed5 |
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