Supervisors: Dr Tomas Cizmar and Prof Kees Weijer
High-resolution imaging deep within tissues of the human body is currently one of the most exciting challenges for BioPhotonics. Tools available to researchers currently include powerful instruments like Confocal and Multiphoton microscopes to produce high-quality three-dimensional images of the objects. However, the depth of imaging is limited by the optical properties of the tissue itself. Variations in the refractive index of the biological specimen can lead to significant aberrations in focusing through a thick sample and decrees a quality of the image. Also these methods are hardly applicable for some of the in-vivo imaging, for example for motile objects or hardly accessible places within the organism.
Here endoscopes can play their role, combining minimally invasive access with a small footprint and comparably high resolution. A recent trend in the development of endoscopes introduces hair-thick multimode optical fibres as image guiding medium to significantly minimize the footprint. Multimode fibres, in comparison to well-developed analogue fibre bundles, can carry the same amount of information (image) encoded in the propagating modes. Mode mixing and dispersion rapidly shuffle amplitude and phase of the propagating modes that transform initial image to speckle pattern and prevent direct decoding of the information.
A few years ago pioneering work in this field showed that, even though light transport processes within multimode waveguides are extremely complex, they can be empirically characterized. With this knowledge, we can predict the outcome of any optical field being coupled to the fibre or design any output optical field by pre-shaping the light at the input side . The most critical drawback of this method is the lack of flexible operation. Once a system is characterized, any bending or looping of the fibre leads to significant decreasing of imaging quality.
Very recently, Dr. Tomas Cizmar and co-workers from the University of Dundee demonstrated that, because of the cylindrical symmetry of optical fiber, propagation of light through the multimode fibre as well as changing in propagation properties due to bending could be theoretically predicted with sufficient precision for the purposes of minimally invasive endoscopy .
This project started in July 2015 and is focused on building a new Digital Micromirror Device (DMD) based system for imaging through the multimode fibre. Employing DMD can significantly increase the speed of imaging up to the real-time regime. It can open the possibility of monitoring fast processes in the tissues as well as decreasing photodamage and photobleaching effect in the samples.
In collaboration with the University of Edinburgh, a previously developed fibre imaging setup for ex-vivo experiments is being applied to imaging cells of the visual cortex of the animal model. First results showed promising perspectives of such systems for deep brain imaging applications and gave additional motivation for developing a new real-time system, which could allow in-vivo experiments in animal models and provide new instrumental background for optogenetic research approaches.
- Mosk, Allard P., et al. “Controlling waves in space and time for imaging and focusing in complex media.” Nature photonics 6.5 (2012): 283-292.
- Plöschner, Martin, Tomáš Tyc, and Tomáš Čižmár. “Seeing through chaos in multimode fibres.” Nature Photonics 9.8 (2015): 529-535.
Journal and Conference Papers and Posters
[November 2017] 3-D holographic optical manipulation through high-NA soft-glass multimode fibre, Ivo Leite, Sergey Turtaev, Xin Jiang, Alfred Cuschiere, Philip St.J. Russell and Tomas Cizmer. Nature PHotonics, accepted for publication (2017).
[November 2017] Comparison of nematic liquid-crystal and DMD-based spatial light modulation in complex photonics, Sergey Turtaev, Ivo T. Leite, Kevin J. Mitchell, Miles J. Padgett, David B. Phillips and Tomas Cizmar. Optics Express Vol. 25, pp. 29874-29884.
[January 2017) Novel single-fibre probes for advanced biophotonic applications, Ivo Leite, Sergey Turtaev, Xin Jiang, Philip St. J. Russel and Thomas Cizmer. Poster presented at SPIE BiOS, Adaptive Optics and Wavefront Control for Biological Systems III, San Francisco, USA, 30th January 2017.
[January 2017] High-speed wavefront modulation in complex media, Sergey Turtaev, Ivo Leite and Tomas Cizmar. Paper presented at SPIE BiOS, Adaptive Optics and Wavefront Control for Biological Systems III, San Francisco, USA, 30th January 2017.
[December 2016] High-speed spatial control of the intensity, phase and polarisation of vector beams using a digital micro-mirror device, Kevin J. Mitchell, Sergey Turtaev, Miles J. Padgett, Tomáš Čižmár, and David B. Phillips. Optics Express Vol. 24, Issue 25, pp. 29269-29282 (2016). [OPEN ACCESS] Most downloaded Optics Express paper during December 2016.
[August 2016] Accelerating wavefront shaping in complex environment. Oral presentation at the Biophotonic approaches: From molecules to living systems conference, Dundee, Scotland, 23rd August 2016.
[June 2016] Dark soliton generation from semiconductor optical amplifier gain medium in ring fiber configuration. Poster presented at Laser Optics 2016, Saint Petersburg, Russia, 30th June 2016.
[May 2016] Holographic optical tweezing via a multimode fibre by I. Leite, S. Turtaev, Xin Jiang, Philip St. J. Russell, and Tomas Cizmar. Poster presented at SUPA 2016 Annual Gathering, Glasgow, Scotland.
[May 2016] High-resolution holographic micro-endoscopy and manipulation by I. Leite, S. Turtaev, Alfred Cuschieri, and Tomás Čižmár. Poster presented at Highland Spring School on Mesoscopic Physics, Trest, Czech Republic.
[December 2015] Multimode fibres for micro-endoscopy, Turtaev, Sergey / Leite, Ivo T. / Čižmár, Tomáš. Optofluidics, Microfluidics and Nanofluidics. Volume 2, Issue 1, Pages 31–35. [OPEN ACCESS]
[June 2015] Tunable visible dual-wavelength SHG from a diode-pumped PPKTP waveguide by K.A. Fedorova, Sergey Turtaev, I.O. Bakshaev, D.A. Livshits, and E.U. Rafailov. Poster presented at CLEO®/Europe-EQEC 2015, Munich, Germany.