Cryogenic scattering near-field optical microscopy for probing optical properties with 20nm spatial resolution at temperatures < 10K

Scattering-type near-field microscopy (s-SNOM) has proven to be a powerful technology for probing the local optical properties of modern nanomaterials. It enables applications such as chemical identification, free-carrier profiling, and the direct mapping and measurement of the dispersion relation of propagating plasmon, phonon, and exciton polaritons in layered materials.

Transferring these capabilities to cryogenic temperatures opens new avenues for characterizing novel materials and their fundamental properties.



By integrating an s-SNOM into an ultra-stable, vibrationally damped, and automated closed-cycle cryostat system, we have developed the first commercial cryogenic s-SNOM microscope. This unique system supports near-field amplitude and phase-resolved imaging and spectroscopy in the visible to THz spectral range, operating in a variable temperature range from below 10K to room temperature.

In this presentation we will introduce the design of the cryogenic s-SNOM microscope. Furthermore, we will demonstrate infrared and visible near-field imaging and spectroscopy with deep subwavelength spatial resolution, visualizing phonon polariton modes in hBN and exciton polariton waveguide modes in MoS₂ at temperatures below 10K.