Synchronously pumped Raman laser for simultaneous degenerate and nondegenerate two-photon microscopy.

Two-photon fluorescence microscopy is a nonlinear imaging modality frequently used in deep-tissue imaging applications. A tunable-wavelength multicolor short-pulse source is usually required to excite fluorophores with a wide range of excitation wavelengths. This need is most typically met by solid-state lasers, which are bulky, expensive, and complicated systems. Here, we demonstrate a compact, robust fiber system that generates naturally synchronized femtosecond pulses at 1050 nm and 1200 nm by using a combination of gain-managed and Raman amplification. We image the brain of a mouse and view the blood vessels, neurons, and other cell-like structures using simultaneous degenerate and nondegenerate excitation.