Multi-wavelength Lissajous fibre scanner using photonic crystal fibres

We report a Lissajous fibre scanner based on photonic crystal fibres (PCFs) with mode-stripping, multi-wavelength dual numerical aperture confocal detection using a multi-channel photodiode. The fibres are dip-coated in polymer to form a dual-cylindrical structure with two non-degenerate orthogonal bending modes. The fibres are held parallel using silicon V-grooves during dip coating, with the open ends sealed using UV-curing epoxy. The coating method is shown to be effective and controllable, enabling dense scanning patterns to be generated under piezoelectric excitation. The mode-stripping detection efficiency of PCFs is characterised using a monochromator and multi-channel photodiodes, with single-mode fibres serving as a reference. A two-dimensional fibre scanner is then constructed using the coated PCF and RGB laser sources. Coloured coatings on a metal aperture provide distinguishable optical feedback for the x- and y-motions under monochromatic blue or multiplexed RGB illumination, enabling real-time switching between fluorescence and full-colour imaging modes. Fluorescence imaging is demonstrated using a USAF 1951 target and spinach soaked in ethanol, while full-colour imaging that closely matches conventional microscope imaging is achieved by calibrating the photodiode responses against a ColorChecker. The performance of the scanner is further validated through calibrated imaging of a UK postage stamp and a prepared slide of a Zea grass stem cross-section.