Surface Phonon Polariton Resonance Imaging Using Long-Wave Infrared-Visible Sum-Frequency Generation Microscopy

Riko Kiessling,Yujin Tong,Sandy Gewinner,Alexander Paarmann,Joshua D Caldwell,Wieland Schöllkopf,Alexander J Giles,Martin Wolf

doi:10.1021/acsphotonics.9b01335

Abstract

We experimentally demonstrate long-wave infrared-visible sum-frequency generation microscopy for imaging polaritonic resonances of infrared (IR) nanophotonic structures. This nonlinear-optical appr...

Highlights

Nanophotonics relies on the subdiffractional localization of light, which is typically achieved using largemomentum surface polariton modes.[1,2] This has been demonstrated for a large variety of structures, using both plasmon polaritons in metallic nanoantennas[3−5] as well as phonon polaritons in subdiffractional polar dielectric nanostructures,[6−13] emerging in the visible (VIS) and long-wave infrared (LWIR) spectral regions, respectively
We experimentally demonstrate long-wave infrared-visible sum-frequency generation microscopy for imaging polaritonic resonances of infrared (IR) nanophotonic structures
As a perspective approach toward overcoming this limitation, we discuss the concept of using widefield sum-frequency generation microscopy as a universal experimental tool that would offer long-wave IR super-resolution microscopy with spatial resolution far below the IR diffraction limit

Summary

ACS Photonics

Microscopy well below the IR diffraction limit. far, such studies have been hindered by the scarcity of high-intensity laser sources in the LWIR spectral region relevant for nanophotonics based on surface phonon polaritons (SPhPs). The sensitivity could be further improved by tuning the VIS wavelength to a resonant electronic transition,[62] e.g., to the band gap of the semiconductor under study Such double-resonant SFG microscopy would provide drastically enhanced signal levels and additional imaging contrast due to the spatial variations of the electronic resonance. For heterogeneous materials, such as semiconductor superlattices, this approach could serve as a contrast mechanism between the individual constituents.[2,45] we expect LWIR-VIS SFG microscopy introduced here to be implemented for studying biological and chemical systems, for instance, for probing the spatial heterogeneity of transient low-frequency modes of transient species at electrochemical interfaces.[63−65].

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