Non-linear label-free imaging through a multimode graded index optical fibre

¹ Institute of Scientific Instruments of the CAS, v. v. i., Královopolská 147, 612 64 Brno, Czech Republic
² Leibniz Institute of Photonic Technology, Albert-Einstein-Straße 9, 07745 Jena, Germany
³ Institute of Physical Chemistry, Friedrich Schiller University of Jena and Abbe Center of Photonics, Helmholtzweg 4, 07743 Jena, Germany
⁴ CREOL, The College of Optics and Photonics, University of Central Florida, 4304 Scorpius St., 32816-2700 Orlando, Florida, United States of America
⁵ Institute of Applied Optics, Friedrich Schiller University Jena, Fröbelstieg 1, 07743 Jena, Germany

^* Corresponding author: cifuentes@isibrno.cz

Published online: 20 August 2020

Abstract

In recent years, great advances have been made in developing minimal footprint micro-endoscopes using multimode optical fibres (MMF) [1]. By employing wavefront shaping methods the seemingly random speckle pattern resulting from the guiding of coherent light through an MMF can be formed into a diffraction limited spot. This enables the implementation of multiple laser scanning techniques. In this work we show that this approach can be employed to realize label-free non-linear microscopy techniques such as coherent anti-Stokes Raman scattering (CARS) and second harmonic generation (SHG). Backscattered light makes epi-detection possible even though these processes preferably emit light in the direction of beam propagation [2].