MULTIPHOTON MICROSCOPY SYSTEMS

Multiphoton microscopy is a fluorescence imaging technique that allows imaging of living tissue up to about one millimeter in depth. It uses red-shifted excitation light, which can also excite fluorescent dyes. However, for each excitation, two photons of low energy infrared light are absorbed simultaneously to provide the required energy for electrons in the fluorophore to reach the excited state. Using infrared light minimizes scattering in the tissue. Due to the multiphoton absorption, the background signal is strongly suppressed. Both effects lead to an increased penetration depth for these microscopes.