CARS Microscopy Made Simple: Label-free Molecular Imaging

We discuss a very simple yet high performance CARS microscopy, recently commercialized by Olympus, based on a single fs Ti:Sapphire oscillator combined with a photonic crystal fibre. By optimally shaping the femtosecond laser pulses, we achieve high quality multi-modal imaging (simultaneous CARS, two-photon fluorescence, and second harmonic generation) of live cells and tissues with a Raman tuning range from below 900 cm-1 to over 4000 cm-1.  Laser pulse shape as a control parameter permits simultaneous optimization of the spectral resolution and signal levels of these imaging modalities. We discuss recent technical developments such as all-fibre CARS microscopy, Hilbert Transform CARS, and time-correlated photon counting FLIM-CARS microscopy. We illustrate with applications of multi-modal CARS microscopy to label-free, molecule-specific biomedical, biomaterial and geological imaging.