Life Beyond Diffraction: Opening New Routes to Materials Characterization with Next-Generation Optical Near-Field Approaches

Near-field optical microscopies and spectroscopies seek to investigate materials by combining the best aspects of optical characterization and scan-probe microscopy techniques. In principle, this provides access to chemical, morphological, physical and dynamical information at nanometer length scales that is impossible to access by other means. But a number of challenges, particularly on the scan-probe front, have limited the widespread application of near-field investigations. This work describes how recent probe engineering and technique innovation have addressed many of these challenges. This Feature Article begins with a short overview of the field, providing perspective and motivation for these developments and highlighting some key improvements. This is followed by a more in-depth description of the near-field advances developed at the Molecular Foundry, a national nanoscience User Facilityadvances that provide groundwork for generally-applicable nano-optical studies. Finally, a discussion is provided of what progress is still needed in order to realize the ultimate objective of translating all optical measurements to the nanoscale.