Toward phase-imaging optical nanoscopes
Observation-based measurements are fundamental to science since imaging provides a quick and direct way to collect data, experiment, and test hypothesis in applications big and small. Technology advancements consumer components get smaller, faster, and demand better performance capabilities. Manufacturing these goods requires the ability to faithfully image the material during processing to identify any possible defect early on. As things get smaller, the usefulness of an optical microscope for these tests is quickly diminishing. In the medical field, tests for early detection of diseases rely on fast non-invasive analysis of pre-identified triggers. Unfortunately, in the bio-field, the identifying characteristics of a diseased cell for example are beyond the resolution of a typical optical microscope. These rapid advancements in technology highlight the need for an easily accessible optical nanoscope. For my thesis, I have helped develop and demonstrate the capabilities of a phase recovery microscopy technique that combines innovations in condenser technology and phase recovery algorithms. The phase recovery algorithms produce reconstructed high-resolution real plane images by creating a large synthetic-numerical aperture Fourier plane image from sets of low-resolution experimental images. This type of algorithm not only allows us to image the intensity profile of the incident electric field, but it also gives us information about the unmeasured phase. When used in conjunction with a high-numerical aperture condenser, such as the surface plasmon polariton-based Ultra-Thin Condenser, these algorithms can image periodic structures with periods beyond the Rayleigh resolution limit. The work developed for this thesis demonstrates that, with the realization of a carefully designed high-numerical aperture condenser, the phase-recovery microscopy technique can indeed function as an optical nanoscope.