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This perspective highlights recent advances in super-resolution, mid-infrared imaging and spectroscopy. It provides an overview of the different near field microscopy techniques developed to address the problem of chemically imaging specimens in the mid-infrared “fingerprint” region of the spectrum with high spatial resolution. We focus on a recently developed far-field optical technique, called infrared photothermal heterodyne imaging (IR-PHI), and discusses the technique in detail. Its practical implementation in terms of equipment used, optical geometries employed, and underlying contrast mechanism are described. Milestones where IR-PHI has led to notable advances in bioscience and materials science are summarized. The perspective concludes with a future outlook for robust and readily accessible high spatial resolution, mid-infrared imaging and spectroscopy techniques.
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This content will become publicly available on May 1, 2027
Video-rate mid-infrared imaging in the molecular fingerprint region via nanosecond non-degenerate two-photon absorption
Non-degenerate two-photon absorption (NTA) offers an attractive route for wide-field mid-infrared imaging by mapping long wavelength information into the spectral detection windows of mature near-infrared detector technologies. However, existing NTA implementations rely almost exclusively on complex, large-footprint femtosecond laser systems, severely limiting practicality and scalability. Here, we demonstrate an NTA imaging platform that replaces the ultrafast laser with a compact nanosecond mid-IR source coupled to a high-definition indium gallium arsenide camera. Operating in the nanosecond regime removes stringent temporal-overlap requirements, dramatically simplifying system architecture while preserving high detection sensitivity. Using this approach, we achieve chemically selective, wide-field imaging deep into the mid-IR molecular fingerprint region and demonstrate, for the first time, video-rate NTA imaging in this spectrally rich regime. By combining relaxed alignment constraints, compact excitation, and high-speed fingerprint-region imaging, this work establishes nanosecond NTA as a practical and scalable foundation for next-generation mid-IR chemical imaging.
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- Award ID(s):
- 2434622
- PAR ID:
- 10683753
- Publisher / Repository:
- AIP Publishing
- Date Published:
- Journal Name:
- APL Photonics
- Volume:
- 11
- Issue:
- 5
- ISSN:
- 2378-0967
- Page Range / eLocation ID:
- 056112
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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