Nonlinear multi-modality spectro-microscopy: Multi-photon fluorescence, SHG and THG of biological specimen

The non-linear nature of multi-photon fluorescence excitation, SHG and THG restricts the signal detecting volume to the vicinity of the focal point. As a result, the technology has intrinsic optical sectioning capability. The use of multi-photon fluorescence excitation also allows micro-fluorometry at high spatial resolution. Under high intensity illumination, biological specimen not only emits fluorescence, but also generates harmonic emissions. Conventional ultra-fast Ti-sapphire laser allows efficient excitation of most biologically important fluorescent probes and SHG in the deep blue range, in contrast, the use of ultra-fast Cr-forsterite laser makes possible simultaneous detection of two- and three-photon fluorescence, SHG and THG.