Ultrafast coherent Raman with time/spectral compression

Le résumé fourni par la source

Spontaneous Raman microscopy and spectroscopy techniques are useful tools in the processes of disease diagnosis and grading, and drug characterisation and development. That usefulness derives from Raman’s ability to map biomolecular and chemical information in samples, by measuring the intrinsic vibrational modes of their molecular contents, without the requirement of labels. However, the spontaneous Raman effect suffers from low signal efficiency and thus slow speed, comparatively to other methods, which limits its capabilities in high throughput imaging. To overcome these inherent challenges, coherent Raman scattering (CRS), specifically Stimulated Raman Scattering (SRS) and Coherent Anti-Stokes Raman Scattering (CARS), have gained recognition and prominence. The enhanced sensitivity and timescale of these techniques offer a framework which makes the measurement and imaging of complex biological systems more achievable. CRS exhibits suitable rates for live imaging, while providing appropriate information for molecular identification and classification. Our work deploys a picosecond (ps) narrowband laser system which rapidly oscillates the frequency of the input Stokes beam within a laser scanning microscope for the purposes of hyperspectral CRS microscopy. The resulting signal is processed via a multi-channel lock-in amplifier. Many current systems rely on the use of a femtosecond, spectrally broadband laser input, with the necessary spectral filtering of resulting signal for molecular fingerprinting. The spread of peak power across the laser band puts a tight limit on their signal generation efficacy at each wavelength and makes them unsuitable for adoption with fibre optics and future endoscopic applications. Instead, fast tuneable, narrowband source can rapidly address the same spectral coverage with higher signal efficiency per wavelength and also with higher potential for adoption within fibre optical systems in view of using picosecond pulses, thereby promising strong flexibility in the application of in vivo, real-time imaging for collection of biochemical information.

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