@article {3471, title = {Side-view holographic endomicroscopy via a custom-terminated multimode fibre}, journal = {Opt. Express}, volume = {29}, year = {2021}, pages = {23083{\textendash}23095}, abstract = {

Microendoscopes based on optical fibres have recently come to the fore as promising candidates allowing in-vivo observations of otherwise inaccessible biological structures in animal models. Despite being still in its infancy, imaging can now be performed at the tip of a single multimode fibre, by relying on powerful holographic methods for light control. Fibre based endoscopy is commonly performed en face, resulting in possible damage of the specimen owing to the direct contact between the distal end of the probe and target. On this ground, we designed an all-fibre probe with an engineered termination that reduces compression and damage to the tissue under investigation upon probe insertion. The geometry of the termination brings the field of view to a plane parallel to the fibre\&\#x2019;s longitudinal direction, conveying the probe with off-axis imaging capabilities. We show that its focusing ability also benefits from a higher numerical aperture, resulting in imaging with increased spatial resolution. The effect of probe insertion was investigated inside a tissue phantom comprising fluorescent particles suspended in agarose gel, and a comparison was established between the novel side-view probe and the standard en face fibre probe. This new concept paves the way to significantly less invasive deep-tissue imaging.

}, doi = {10.1364/OE.426235}, url = {http://www.osapublishing.org/oe/abstract.cfm?URI=oe-29-15-23083} } @article {3191, title = {Label-free CARS microscopy through a multimode fiber endoscope}, journal = {Opt. Express}, volume = {27}, year = {2019}, pages = {30055{\textendash}30066}, abstract = {

Multimode fibres have recently been employed as high-resolution ultra-thin endoscopes, capable of imaging biological structures deep inside tissue in vivo. Here, we extend this technique to label-free non-linear microscopy with chemical contrast using coherent anti-Stokes Raman scattering (CARS) through a multimode fibre endoscope, which opens up new avenues for instant and in-situ diagnosis of potentially malignant tissue. We use a commercial 125 \&\#x00B5;m diameter, 0.29 NA GRIN fibre, and wavefront shaping on an SLM is used to create foci that are scanned behind the fibre facet across the sample. The chemical selectivity is demonstrated by imaging 2 \&\#x00B5;m polystyrene and 2.5 \&\#x00B5;m PMMA beads with per pixel integration time as low as 1 ms for epi-detection.

}, doi = {10.1364/OE.27.030055}, url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-27-21-30055} } @article {3190, title = {Wavelength dependent characterization of a multimode fibre endoscope}, journal = {Opt. Express}, volume = {27}, year = {2019}, pages = {28239{\textendash}28253}, abstract = {

Multimode fibres have recently shown promise as miniature endoscopic probes. When used for non-linear microscopy, the bandwidth of the imaging system limits the ability to focus light from broadband pulsed lasers as well as the possibility of wavelength tuning during the imaging. We demonstrate that the bandwidth is limited by the dispersion of the off-axis hologram displayed on the SLM, which can be corrected for, and by the limited bandwidth of the fibre itself. The selection of the fibre is therefore crucial for these experiments. In addition, we show that a standard prism pulse compressor is sufficient for material dispersion compensation for multi-photon imaging with a fibre endoscope.

}, doi = {10.1364/OE.27.028239}, url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-27-20-28239} }