Paiella, RobertoGok, Abdullah2022-09-062022https://hdl.handle.net/2144/45075Optoelectronic devices operating in the visible and near-infrared spectral regions have driven increasing interest due to their potential to provide distinctive features and functionalities for applications in a wide range of disciplines. Starting from this motivation, I have developed a novel method to design and fabricate semiconductor heterostructures, which represent a fundamental building block of many optoelectronic devices such as lasers, LEDs, solar cells, and thermoelectrics. This method consists of introducing variations in bandgap energy with lateral position utilizing strain engineering and tailoring the mechanical properties of ultra-thin nanomembranes. We employ a specially designed pressure cell to apply in-plane stress on Ge thin films coated with square arrays of amorphous-Si pillars. As a result, a non-uniform strain distribution is created in the film, which is commensurate with the sample thickness variations caused by the pillar array. Since strain modifies the bandgap energy, a bandgap modulation is correspondingly obtained in Ge film. This approach can be applied to material platforms with uniform chemical composition, and therefore is not limited by lattice matching requirements. Moreover, this approach allows for active tunability of the energy band lineups employing the controlled introduction of strain and provides great freedom to pattern these lineups in nearly arbitrary profiles. In the second part of this dissertation work, I have developed a new type of combiner optics for head mount displays (HMDs) in augmented reality (AR) and virtual reality (VR) applications. I have designed and implemented millimeter-long, multi-mode waveguide combiners built with lossless dielectric materials. These combiners are very compact and therefore can meet the tight volume requirements of HMDs. Additionally, they feature a single emission point in the output, which is particularly important for AR/VR applications in order to achieve sufficient alignment/compatibility between the human visual system and the display system. In contrast, conventional AR/VR display optics cause insufficient image formation due to limited field of view, and discomfort because of the generation of multiple image planes to create virtual 3D images. Moreover, our combiners eliminate the need for multiple optical paths for emission and auxiliary optical components such as lenses and beam splitters to channel the generated augmented image. This is a key property to eliminate the compensating optics/electronics and minimize the form factor of the final HMD optics. Therefore, our combiners allow for the realization of lightweight HMDs for a comfortable and immersive AR/VR experience. Finally, due to their multi-mode nature, these combiners can provide an incoherent, robust, and uniform output beam which is essential to natural-looking image formation.en-USElectrical engineeringThesis/Dissertation2022-08-30