In vivo coherent anti-Stokes Raman scattering imaging of sciatic nerve tissue.

We report in vivo nonlinear optical imaging of mouse sciatic nerve tissue by epidetected coherent anti-Stokes Raman scattering and second harmonic generation microscopy. Following a minimally invasive surgery to open the skin, coherent anti-Stokes Raman scattering imaging of myelinated axons and second harmonic generation imaging of the surrounding collagen fibres were demonstrated with high signal-to-background ratio, three-dimensional spatial resolution, and no need for labelling. The underlying contrast mechanisms of in vivo coherent anti-Stokes Raman scattering were explored by three-dimensional imaging of fat cells that surround the nerve. The epidetected coherent anti-Stokes Raman scattering signals from the nerve tissues were found to arise from interfaces as well as back reflection of forward coherent anti-Stokes Raman scattering.