Coherent Raman mixing and coherent anti-Stokes Raman scattering from individual micrometer-size droplets

AbstractThis paper is a brief overview to coherent anti- Stokes Raman spectroscopic technique and introduces the strengths and barriers to its use all based on the interpretation of simple theoretical formulae. The use of the Gaussian ultrashort pulses is highlighted as a practical elucidatory reconstruction tool of coherent Raman spectra. The paper presents the integral formulae for coherent anti-Stokes and Stokes Raman scattering, and discusses the closed-form solutions, its complex error function, and the delay time formula for enhancement of the inferred pure coherent Raman spectra. As an example, the timeresolved coherent Stokes Raman scattering experimental observations are quantitatively elucidated.Understanding the essentials of coherent Raman spectroscopy, therefore, promotes the importance of a number of experiments including the ones utilizing a broadband excitation with a narrowband delayed probing for successful background suppression.

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Multiplex coherent anti-Stokes Raman scattering highlights state of chromatin condensation in CH region

Scientific Reports ◽

10.1038/s41598-019-50453-0 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 4

Author(s):

Tiffany Guerenne-Del Ben ◽

Zakaniaina Rajaofara ◽

Vincent Couderc ◽

Vincent Sol ◽

Hideaki Kano ◽

...

Keyword(s):

Cell Cycle ◽

Raman Scattering ◽

Chromatin Condensation ◽

Cellular Level ◽

High Spectral Resolution ◽

Condensed State ◽

Label Free ◽

Coherent Raman ◽

Wavenumber Region ◽

Anti Stokes

Abstract Coherent Raman microscopy has become a powerful tool in label-free, non-destructive and fast cell imaging. Here we apply high spectral resolution multiplex coherent anti-Stokes Raman scattering (MCARS) microspectroscopy in the high wavenumber region to the study of the cell cycle. We show that heterochromatin - the condensed state of chromatin - can be visualised by means of the vibrational signature of proteins taking part in its condensation. Thus, we are able to identify chromosomes and their movement during mitosis, as well as structures like nucleoli and nuclear border in interphase. Furthermore, the specific organization of the endoplasmic reticulum during mitosis is highlighted. Finally, we stress that MCARS can reveal the biochemical impact of the fixative method at the cellular level. Beyond the study of the cell cycle, this work introduces a label-free imaging approach that enables the visualization of cellular processes where chromatin undergoes rearrangements.

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Pulse-picking coherent anti-Stokes Raman scattering microscopy for highly sensitive chemical imaging

10.21203/rs.3.rs-846172/v1 ◽

2021 ◽

Author(s):

Matthew Clark ◽

Gil Gonzalez ◽

Chi Zhang

Keyword(s):

Raman Scattering ◽

Second Harmonic ◽

Laser Pulses ◽

Chemical Imaging ◽

Function Generator ◽

Tissue Samples ◽

Duty Cycles ◽

Highly Sensitive ◽

Coherent Raman ◽

Anti Stokes

Abstract Coherent Raman scattering has been developed into powerful technologies for the chemical imaging of biological samples. However, limited sensitivity remains a critical bottleneck for coherent Raman microscopes. We introduce a pulse-picking technology that can significantly increase the sensitivity of coherent anti-Stokes Raman scattering (CARS) microscopy. An acousto-optic modulator driven by a function generator allows picking collinearly combined pump and Stokes pulses at low duty cycles. This method reduces the number of pulses at each image pixel, enhances the peak power of laser pulses, and thus significantly improves the sensitivity of CARS and minimizes phototoxicity. We demonstrated an over 1000-fold sensitivity improvement for CARS imaging. Besides, we show this pulse-picking method can enhance the sensitivity of multiphoton fluorescence and second harmonic generation modalities about 20 times. Using cell and biological tissue samples, we highlight the potential of this pulse-picking technology for highly sensitive multimodal chemical imaging in biological and medical sciences.

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