Hyperspectral coherent anti-Stokes Raman scattering microscopy imaging through turbid medium

Abstract

Abstract. Coherent Raman microspectroscopy imaging is an emerging technique for noninvasive, chemically specific optical imaging, which can be potentially used to analyze the chemical composition and its distribution in biological tissues. In this report, a hierarchical cluster analysis was applied to hyperspectral coherent anti-Stokes Raman imaging of different chemical species through a turbid medium. It was demonstrated that by using readily available commercial software (Cytospec, Inc.) and cluster analysis, distinct chemical species can be imaged and identified through a rather thick layer of scattering medium. Once the clusters of different chemical composition were distinguished, a phase retrieval algorithm was used to convert coherent anti-Stokes Raman spectra to Raman spectra, which were used for chemical identification of hidden microscopic objects. In particular, applications to remote optical sensing of potential biological threats and to imaging through a layer of skin tissue were successfully demonstrated. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Ultra‐compact tunable fiber laser for coherent anti‐Stokes Raman imaging

“…[15][16][17] So-called hyperspectral CARS microscopy enables efficient signal detection even in turbid media, because also nonballistic photons can be collected by large area single element detectors. [18] For real-time detection of spectral changes, extremely fast tunable laser sources are required. The work presented here aims at the presentation of a compact fiber laser source for the before mentioned approach of hyperspectral CARS microscopy utilizing fast spectrally tuneable narrow band lasers.…”

Higher order processes in random Raman lasing

“…Additionally, random Raman lasing gives us an opportunity to study nonlinear optical effects in a turbid media. A better knowledge of these dynamics will help improve upon applications ranging from chemical analysis in turbid media [19–21] to stimulated Raman induced photoacoustics [22–24]. …”

Molecular Orientation Analysis of Alkyl Methylene Groups from Quantitative Coherent Anti-Stokes Raman Scattering Spectroscopy

“…One important consideration for quantitative CARS spectroscopy is to overcome spectral distortion caused by nonresonant background. Excellent research has shown the ability to acquire useful Raman information by effectively subtracting nonresonant CARS signal using various methods such as heterodyne detection, , maximum entropy method, − and a modified Kramers–Krönig transformation. ,, Another important direction of quantitative CARS microscopy is to sort spectral information into groups to derive chemical composition maps for complicated systems using methods such as principle component analysis, hierarchical cluster analysis, classical least-squares analysis, and singular value decomposition analysis . Additionally, since one of the most important advantages of vibrational spectroscopic techniques is the ability to elucidate complicated molecular structures based on quantitative spectral analysis, CARS has been used to study molecular orientations in a specimen.…”