Super-resolution and spectroscopic fingerprints achieved through pairing of technologies

The individual tools of optical microscopy and single-particle spectroscopy are invaluable for determining structural details in complicated systems. However, technical limitations have prevented the ability to add spectroscopic information to relative positions. Knappenberger and Steves developed a method for simultaneously determining the nonlinear spectra along with the locations of objects at the nanometer level.

“Most imaging methods tell us where something is located but do not provide the spectroscopic fingerprinting needed to identify the object,” said author Kenneth Knappenberger.

By combining Fourier transform-based nonlinear spectroscopy with microscopy, the authors developed a microscope that uses two laser light pulses to excite individual gold nanorods co-located within the optical diffraction limit. A series of time delays between pulses results in the formation of an interferogram data set, allowing for retrieval of spectrally resolved microscopic images of the nanoparticles.

Resonance spectra of the nanorods were also generated. Despite being separated by less than 50 nanometers, the two nearly-identical particles were able to be distinguished and resolved—something that could not have happened using conventional means.

The authors note that further developments in this field could lead to super-resolution capable of sorting chiral enantiomers.

“These capabilities could impact our ability to understand enantioselective catalysis by metals and mechanisms of spin-polarized energy transfer at interfaces,” said Knappenberger.

This method could also be applied to other forms of coherent optical Fourier transform spectroscopies and may be used further to resolve energy transfer mechanisms in molecular and materials systems.

Source: “Achieving sub-diffraction spatial resolution using combined Fourier transform spectroscopy and nonlinear optical microscopy,” by Megan A. Steves and Kenneth Knappenberger, Jr., Journal of Chemical Physics (2022). The article can be accessed at https://doi.org/10.1063/5.0069944 .

This paper is part of The Ever-Expanding Optics of Single-Molecules and Nanoparticles Collection, learn more here .