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

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].