Time-Encoded Raman: Fiber-based, hyperspectral, broadband stimulated Raman microscopy

TL;DR

This paper introduces a fiber-based, broadband stimulated Raman microscopy technique using time-encoded signals with rapid wavelength swept lasers, enabling high-speed, high-resolution, and broad spectral chemical imaging.

Contribution

The authors develop TICO-Raman, a novel all-fiber system employing FDML lasers for fast, broadband, and high-resolution Raman spectroscopy and microscopy.

Findings

Achieved high-speed Raman spectral acquisition with broad spectral coverage.

Demonstrated quantitative analysis of chemical mixtures.

Enabled hyperspectral imaging of biological samples with molecular contrast.

Abstract

Raman sensing and Raman microscopy are amongst the most specific optical technologies to identify the chemical compounds of unknown samples, and to enable label-free biomedical imaging with molecular contrast. However, the high cost and complexity, low speed, and incomplete spectral information provided by current technology are major challenges preventing more widespread application of Raman systems. To overcome these limitations, we developed a new method for stimulated Raman spectroscopy and Raman imaging using continuous wave (CW), rapidly wavelength swept lasers. Our all-fiber, time-encoded Raman (TICO-Raman) setup uses a Fourier Domain Mode Locked (FDML) laser source to achieve a unique combination of high speed, broad spectral coverage (750 cm-1 - 3150 cm-1) and high resolution (0.5 cm-1). The Raman information is directly encoded and acquired in time. We demonstrate quantitative chemical analysis of a solvent mixture and hyperspectral Raman microscopy with molecular contrast of plant cells.