Physics (Internal)

Rings of Light: Using Apogized Radial Beams to Improve Resolution in Solid Immersion Lens Microscopy

This event is part of the PhD Final Oral Exams.

Examining Committee: Bennett Goldberg, Selim Unlu, Thomas Bifano, Shyamsunder Erramilli, David Campbell (Chair)

Abstract: High Numerical Aperture (NA) solid immersion lens (SIL) microscopy has bet­ ter resolution at a given wavelength than any other far-field microscopy technique. This outstanding resolution allows the imaging of subsurface structures several times smaller than the free-space wavelength of the imaging light . High NA SILs are cur­ rently used in technology applications such as photolithography, semiconductor circuit analysis, Raman imaging. and crystal imaging. However, current techniques for SIL microscopy use linearly polarized illumination that has focal spot sizes unsuitably large for several important applications. Radial polarization has been used in several other lower NA microscopy techniques to improve focal spot sizes; but generating and propagating radially polarized light is more difficult than working with linearly po­ larized , fundamental mode Gaussian beams. This dissertation details modeling and experimental results showing radially polarized light combined with apodization and an aplanatic SIL can be used to create a smaller focal spot than current techniques. This dissertation also includes experimental results of a new, free-space technique for apodization and creation of radially polarized light that is capable of quickly chang­ ing the apodization on the fly without hardware modifications. This new apodization technique is also capable of creating arbitrary apodization patterns more accurately than any previous experiment. Increased control over the apodization pattern allows the experimental study of a far wider range of apodization patterns than ever before, potentially leading to further improvements in high-NA focal spot tailoring. Addi­tionally, in situ apodization pattern control allows for new type of composite SIL imaging combining the results of multiple apodization patterns. This dissertation concludes with ideas for future work in apodization mask optimization. An in-depth study of optimizing the 2D apodization pattern to create focal spots tailored to dif­ferent applications would be an interesting and potentially very useful endeavor. We also discusses the possibility of using highly apodized angularly confined beams to direct the focal spot to areas of the SIL previously thought to be unusable.