Porous silicon as a platform for gradient refractive index photonics

optics;microlenses;materials science, ,

Krueger, Neil A

关键词: optics;    microlenses;    materials science, ,;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/95660/KRUEGER-DISSERTATION-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Porous silicon (PSi) is a versatile optical material that is formed by electrochemically etching bulk Silicon (Si). The refractive index of PSi is readily modulated by the electrochemical current density, making PSi inherently applicable to gradient refractive index (GRIN) applications. A GRIN broadly refers to a spatially-varying refractive index, whether discrete or continuous in nature, which offers a means for strategically controlling the flow of electromagnetic radiation. As such, GRINs are useful in different fields such as photonic crystals (PhCs) and transformation optics (TO) for applications including—but not limited to—light sources, imaging, optical communication, and solar energy conversion. This dissertation focuses on utilizing PSi as a platform for GRIN photonics. A modified transfer-printing method was developed to modularly assembly hybrid PSi microcavities (MCs) comprised of a foreign, light-emitting cavity material sandwiched between PSi 1D PhC reflectors formed from flat Si wafers. These hybrid light-emitting MCs were imparted with tunability by the introduction of a PSi cavity coupling layer.Next, Si wafers were patterned with conventional microfabrication techniques to provide a shape-defined path for PSi formation. The shape-defined process has realized light-focusing GRIN square micro-columns with potential on-chip applicability, as well as cylindrical GRIN microlens arrays that could be useful for integration with detector pixels or light-sheet microscopes.Finally, work was conducted on utilizing PSi templates to create visibly transparent GRIN photonic elements. This concept is demonstrated by a combination of thermal oxidation, to create transparent porous silicon dioxide (PSiO2), and infiltration with titanium dioxide (TiO2) by atomic layer deposition, forming optically tunable discrete and continuous PSiO2/TiO2 composite GRINs.