Towards supercontinuum-driven hyperspectral microscopy in the mid-infrared

Mid-IR hyperspectral imaging for label-free histopathology and cytology

“…Due to their large spectral bandwidth, supercontinuum sources exhibit extremely low temporal coherence effectively eliminating speckle in broadband illumination situations. However, applications that require narrow filtering of the supercontinuum may exhibit speckle [60].…”

“…As supercontinuum sources are inherently broadband, their direct use for hyperspectral imaging requires a spectrometer or wavelength selection element. Utilising acoustooptic tuneable filters (AOTF), they can also be operated in a narrowband imaging scheme which has been demonstrated for wavelengths up to 4.5 μm [60,61]. Yet, at any longer wavelengths, there are currently no commercially available AOTFs.…”

Diffraction-limited mid-infrared microspectroscopy to reveal a micron-thick interfacial water layer signature

“…They allow achieving diffraction-limited spatial resolution (aperture size 3 × 3 µm) over the 3.33-2.63 μm range related to the OH stretching band of water (following the Abbe equation, the diffraction limit is 2.53 µm in the case of 2.7 µm wavelength). 35,[56][57][58] Meanwhile, owing to the recent development of infrared laser technology, quantum cascade lasers (QCLs) and supercontinuum generation of lasers (SCLs) have been employed as an alternative high-brilliance infrared radiation source. 51,56,[59][60][61][62][63][64] QCLs have enough power and brilliance to exploit an aperture size smaller than the wavelength of radiation and therefore perform high spatial resolution measurements.…”

Mid-infrared fiber-coupled supercontinuum spectroscopic imaging using a tapered chalcogenide photonic crystal fiber

“…In recent years, several demonstrations of mid-IR spectroscopic imaging using quantum cascade lasers (QCL) [1,2] has emerged resulting in a drastic reduction in acquisition time from hours to minutes, which makes it very attractive for clinical applications. However, only preliminary work has been performed with using supercontinuum (SC) sources for spectroscopic imaging in the mid-IR region [3][4][5]. The use of mid-IR supercontinuum sources for spectroscopic imaging has the potential for covering both the functional group region (2.5-6.7 μm) and part of the fingerprint region (6.7-15 μm) from a single compact source [6][7][8][9], that can be several orders of magnitude brighter than a synchrotron IR beamline [5] whilst being compatible with existing broadband technologies such as Fouriertransform infrared (FTIR) spectrometry and array detectors.…”

“…However, only preliminary work has been performed with using supercontinuum (SC) sources for spectroscopic imaging in the mid-IR region [3][4][5]. The use of mid-IR supercontinuum sources for spectroscopic imaging has the potential for covering both the functional group region (2.5-6.7 μm) and part of the fingerprint region (6.7-15 μm) from a single compact source [6][7][8][9], that can be several orders of magnitude brighter than a synchrotron IR beamline [5] whilst being compatible with existing broadband technologies such as Fouriertransform infrared (FTIR) spectrometry and array detectors. This demonstration represents one of the first steps toward developing SC-based spectroscopic imaging in the mid-IR and is among several results of the European research project MINERVA: MId-to NEaR infrared spectroscopy for improVed medical diAgnostics, that was a collaboration between thirteen organizations from industry and academia across seven European nations with the goal of developing mid-IR technologies for high-volume pathology screening and in-vivo skin surface examination for the early diagnosis of cancer.…”