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We study how nanophotonic structures can be used for determining the position of a nearby nanoscale object with subwavelength accuracy. Through perturbing the near-field environment of a metasurface transducer consisting of nano-apertures in a metallic film, the location of the nanoscale object is transduced into the transducer’s far-field optical response. By monitoring the scattering pattern of the nanophotonic near-field transducer and comparing it to measured reference data, we demonstrate the two-dimensional localization of the object accurate to 24 nm across an area of 2 × 2 μm. We find that adding complexity to the nanophotonic transducer allows localization over a larger area while maintaining resolution, as it enables encoding more information on the position of the object in the transducer’s far-field response.

The electromagnetic properties of ordered hole nanostructures in very thin metal films are characterized using CdSe/CdS nanocrystals (NCs) as nanoprobes. The characterization of the local density of optical states (LDOS) on the nanostructure is possible by the measurement of their photoluminescence decay rate. Statistical measurements are performed in the far field to show the average increase of optical modes. A determinist approach using an active single NC nanoprobe in the near field gives access to a more precise characterization of the LDOS. The optical properties of the structure come from the coupling between localized surface plasmons created by the holes and surface plasmon polaritons. A strong concentration of optical modes is observed around the holes thanks to the active near-field nanoprobe. With different NC orientations, the strong influence of the component perpendicular to the surface in the very near field of the LDOS is observed. Finite differential time domain simulations of the different components of the electric field in the very near field of the structure confirm that the localization of the electric field around the holes is only due to the normal component as observed with the nanoprobe.

An overview of near-field optics is presented with a focus on the fundamental advances that have been made in the field since its inception 30 years ago. A focus is placed on the advancements that have been achieved in instrumentation. These advances have led to a greater generality of use with ultra-low mechanical and optical noise and the ultimate in force sensitivity with near-field optical probes. An emphasis is placed on the importance of fully integrating near-field optics with other imaging and spectroscopic modalities including Raman spectroscopy and electron/ion beam imaging. Important directions in probe design, force feedback methods and scanner flexibility are described. These developing avenues provide considerable optimism for an ever increasing incorporation of near-field optics to help resolve critical problems in fundamental and applied science.

Typical measurements of light in the near-field utilize a photodetector such as a photomultiplier tube or a photodiode, which is placed remotely from the region under test. This kind of detection has many draw-backs including the necessity to detect light in the far-field, the influence of background propagating radiation, the relatively narrowband operation of photodetectors which complicates the operation over a wide wavelength range, and the difficulty in detecting radiation in the far-IR and THz. Here we review an alternative near-field light measurement technique based on the detection of optically induced forces acting on the scanning probe. This type of detection overcomes some of the above limitations, permitting true broad-band detection of light directly in the near-field with a single detector. The physical origins and the main characteristics of optical force detection are reviewed. In addition, intrinsic effects of the inherent optical forces for certain operation modalities of scanning probe microscopy are discussed. Finally, we review practical applications of optical force detection of interest for the broader field of the scanning probe microscopy.

The integration of near-field scanning optical microscopy (NSOM) with the imaging and localized excitation capabilities of electrons in a scanning electron microscope (SEM) offers new capabilities for the observation of highly resolved transport phenomena in the areas of electronic and optical materials characterization, semiconductor nanodevices, plasmonics and integrated nanophotonics. While combined capabilities for atomic force microscopy (AFM) and SEM are of obvious interest to provide localized surface topography in concert with the ease and large spatial dynamic range of SEM and dual beam imaging (e.g., in-situ AFM following focused ion beam modification), integration with near-field optical imaging capability can also provide access to localized transport phenomena beyond the reach of far-field systems. In particular, the flexibility that is achieved with the capability for independent, high resolution placement of an electron source, providing localized excitation in the form of free carriers, photons or plasmons, with scanning of the optical collecting tip allows for unique types of “dual-probe” experiments that directly image energy transfer. We review integrated near-field and electron optics systems to date, highlight applications in a variety of fields and suggest future directions.