The amplitude and phase of higher order eigenmodes in interacting optical nanostructures has been imaged with 50nm resolution using a 150nm near-field scanning optical microscope (NSOM) collection mode aperture.

Recent Advance By Nanonics Customer: Seo, E., Jin, Y., Choi, W. et al. Near-field transmission matrix microscopy for mapping high-order eigenmodes of subwavelength nanostructures. Nat Commun 11, 2575 (2020).

The group at Korea University and Samsung Advanced Institute of Technology combined a Nanonics MultiView 2000 system with a spatial light modulator and nanometric collection of light without any optical background. This has allowed:

  • Visualization of the formation and coupling of the fundamental optical modes of the interacting nanophotonic system
  • Coupling these modes with the other spatially and spectrally overlapped modes
  • Reaching a resolution that was 1/3 the diameter of the near-field optical imaging aperture of 150nm.

Why is that Important?

The techniques developed in this publication will have important implications as optical nanostructures are designed to achieve greater density for merging multiple functionalities on one chip.  The methodologies will address the challenges ahead in engineering the hybridized modes having distinct resonances with minimal cross-talk.

This addition to conventional NSOM addresses the issues of multiple near-field optical eigenmodes and the part they play in the functionalization of optical devices based on interacting optical structures. Inevitably, these eigenmodes are highly multiplexed in their spectra and superposed in their spatial distributions. 

The elegant application of the optical polarization of the Nanonics’ optical fiber probe with the flexibility and free optical axis of the sample and probe scanners in the Nanonics MV2000 extends nano-optical measurement technology to enable :

  • Mapping out higher orders of individual eigenmodes of structures interacting on a scale of <150nm.
  • Allowing the extraction of orthogonal near-field eigenmodes such as anti-symmetric and quadruple modes of multiple optical nanostructures that are smaller than the probe aperture dimension.
  • Permitting the separate mapping of multiple hybridized and superposed eigenmodes that are formed by the coupling between the modes of the constituent nanostructures.
  • Constructing a fully phase-referenced far- to near-field transmission matrix (FNTM), which describes the far-field input to near-field output response of the given nanostructures and visualize the antisymmetric mode, quadruple mode, and other high-order modes which were completely hidden under the conventional NSOM images, and to quantify their relative coupling efficiency from their eigenvalues.