Three-dimensional near-field analysis through peak force scattering-type near-field optical microscopy

Area of Science:

• Condensed Matter Physics
• Nanophotonics
• Materials Science

Background:

• Scattering-type scanning near-field optical microscopy (s-SNOM) is crucial for studying polaritonic behavior in 2D materials at the nanoscale.
• s-SNOM excites phonon polaritons in 2D materials, visualized as interference fringes, but cannot probe near-field properties perpendicular to the surface.

Purpose of the Study:

• To develop and demonstrate a 3D near-field analysis technique for 2D materials.
• To investigate the momentum quantization of polaritons in confined structures and the influence of tip-sample distance on polaritonic modes.

Main Methods:

• Utilized peak force scattering-type near-field optical microscopy (PF-SNOM) to obtain 3D near-field response cubes.
• Analyzed micro-disk and reflective edge structures made of isotopically pure hexagonal boron nitride (h-11BN).

Main Results:

• Successfully revealed in situ momentum quantization of polaritons due to confinement in a circular structure.
• Demonstrated that tip-sample distance can fine-tune polariton momentum and modify the superposition of quantized polaritonic modes.
• PF-SNOM-based 3D analysis provides high spatial resolution for mapping near-fields.

Conclusions:

• PF-SNOM offers enhanced characterization capabilities for nano-photonics and polaritonic structures.
• The study provides a method to fully map 3D near-fields, advancing the understanding of polaritonics in 2D materials.