Pseudoheterodyne interferometry for multicolor near-field imaging.

Area of Science:

• Nanophotonics
• Spectroscopy
• Microscopy

Background:

• Scattering-type scanning near-field optical microscopy (s-SNOM) is crucial for nanoscale material characterization.
• Simultaneous multi-wavelength imaging in s-SNOM is limited, hindering comprehensive analysis.
• Accurate phase imaging is essential for detecting weak infrared absorption signals.

Purpose of the Study:

• To develop and characterize a novel detection technique for s-SNOM enabling simultaneous near-field amplitude and phase imaging at multiple wavelengths.
• To implement and validate multispectral pseudoheterodyne (PSH) interferometry in a commercial s-SNOM system.
• To demonstrate the technique's utility in correcting negative phase contrast (NPC) for reliable nanoscale infrared absorption imaging.

Main Methods:

• Development of multispectral pseudoheterodyne (PSH) interferometry by combining infrared lasers to create a discrete spectrum.
• Implementation of a time-multiplexing scheme for a single infrared detector.
• Integration and validation of the multispectral PSH technique into a commercial s-SNOM instrument.

Main Results:

• Successful implementation and characterization of multispectral PSH interferometry in s-SNOM.
• Demonstration of real-time correction of negative phase contrast (NPC) for improved nanoscale imaging.
• Reliable imaging of weak infrared absorption at the nanoscale achieved.

Conclusions:

• Multispectral PSH interferometry enhances s-SNOM capabilities for simultaneous multi-wavelength imaging.
• The technique offers potential for improved data throughput and reduced drift effects.
• This advancement paves the way for multicolor s-SNOM imaging as a standard modality, especially with emerging infrared light sources.