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Spectroscopic near-field microscopy using frequency combs in the mid-infrared
Optics Express
|June 17, 2009
Summary
We developed a new spectroscopic near-field optical microscopy technique. It captures broad infrared spectra at each pixel, enabling background-free mid-infrared imaging with time-resolved motion detection.
Area of Science:
- Spectroscopy
- Optical Microscopy
- Nanotechnology
Background:
- Traditional infrared spectroscopy lacks spatial resolution.
- Near-field optical microscopy (NSOM) offers nanoscale resolution but often suffers from background noise.
- Broadband spectral acquisition in NSOM is challenging.
Purpose of the Study:
- To introduce a novel spectroscopic near-field optical microscopy technique.
- To achieve broadband mid-infrared spectral imaging with high spatial resolution.
- To overcome background artefacts in near-field measurements.
Main Methods:
- Utilizing two coherent beams with harmonic frequency-comb spectra for illumination and reference.
- Employing multi-heterodyne detection for scattered light analysis.
- Implementing a 10-microsecond "snapshot" acquisition for rapid spectral recording and background suppression.
Main Results:
- Demonstrated broadband mid-infrared near-field imaging.
- Acquired 200 cm(-1) wide amplitude and phase spectra centered at 950 cm(-1), tunable from 700 to 1400 cm(-1).
- Achieved near-field imaging essentially free of background artefacts due to rapid spectral acquisition.
Conclusions:
- The developed technique provides high-resolution, background-free broadband mid-infrared spectroscopic imaging.
- The method allows for time-resolved analysis of sample dynamics.
- This advancement opens new possibilities for nanoscale chemical analysis in the mid-infrared spectrum.
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