Pure optical contrast in scattering-type scanning near-field microscopy

Area of Science:

• Optics and Photonics
• Nanotechnology
• Materials Science

Background:

• Apertureless scattering-type scanning near-field optical microscopy (s-SNOM) is crucial for nanoscale optical analysis.
• Existing s-SNOM techniques can suffer from height-induced artifacts, limiting true near-field recording.
• Accurate optical near-field characterization is essential for understanding light-matter interactions at the nanoscale.

Purpose of the Study:

• To enhance apertureless s-SNOM for artifact-free near-field recording.
• To introduce and validate novel detection and demodulation techniques for improved s-SNOM performance.
• To demonstrate the capability of the enhanced s-SNOM for high-resolution optical imaging.

Main Methods:

• Implementation of interferometric detection for scattered light analysis.
• Integration of higher-harmonic dither demodulation of the scattered signal.
• Experimental validation using infrared (10 µm) and visible (633 nm) light sources.

Main Results:

• Achieved true near-field recording without height-induced artifacts.
• Demonstrated simultaneous imaging of optical near-field phase and amplitude.
• Obtained sub-10 nm resolution in the visible light experiment operating in heterodyne mode.

Conclusions:

• The combined techniques of interferometric detection and higher-harmonic demodulation significantly improve s-SNOM capabilities.
• The enhanced s-SNOM provides artifact-free, high-resolution imaging of optical near fields.
• This advancement opens new possibilities for nanoscale optical characterization and material analysis.