Brillouin imaging has recently emerged as a powerful technique for its ability to give insight to the mechanical properties of biomaterial. It exploits inelastic scattering of light by acoustic vibrations and maps the tissue stiffness point by point with micron resolution. The non-invasive, real-time nature of the measurements also makes it a potent candidate for in-vivo imaging of live cells and tissues. This, however, has to rely on a compact and flexible apparatus, a Brillouin endoscope, for remote access to specimen parts.
One of the main challenges encountered in the construction of Brillouin endoscope is that the inelastic scattering in the fibre conduit itself is orders of magnitude stronger than the Brillouin signal scattered by the specimen. This is because the length of the fibre endoscope (meters) is orders of magnitude larger than the imaging volume (microns). The problem can be overcome if the scattered light is collected by a separate fibre and does not mix with the fibre scattering inside the delivery channel.
Here we present an all-fibre integrated Brillouin microspectroscopy system that exploits the paths separation between delivery and collection channels. The experimental setup consists of a pair of standard silica single-mode fibres coupled to a graded-index lens and illuminated with a 671nm continuum wavelength source. We test our system performance on liquid samples of water and ethanol and confirm Brillouin shifts of 5.9 GHz and 4.6 GHz, respectively. More importantly, we do not observe any signals corresponding to Brillouin shift in the fibre, in agreement with expectation.
Yuchen Xiang, ChengZe Song, William J. Wadsworth, Carl Paterson, Peter Török, and Irina V. Kabakova, "Brillouin endoscope, design and optimization strategies (Conference Presentation)," Proc. SPIE 10067, Optical Elastography and Tissue Biomechanics IV, 100670O (Presented at SPIE BiOS: January 29, 2017; Published: 24 April 2017); https://doi.org/10.1117/12.2252263.5380018834001.
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