Carbon nanotube-synchronized dual-color fiber laser for coherent anti-Stokes Raman scattering microscopy

In this Letter, we present a passively synchronized dual-color fiber laser at 1.03 and 1.53 µm for coherent anti-Stokes Raman scattering (CARS) microscopy. This fiber laser consists of both Yb- and Er-doped laser cavities, combined by an ∼1.2m common branch with a single-walled carbon-nanotube-based saturable absorber. Stable passively synchronized mode-locked state is obtained within a total cavity length mismatch of 50 µm. We demonstrate the capability of the synchronized dual-color fiber laser for CARS spectroscopy in both low- and high-wavenumber regions, with a resolution of 6.6cm^-1. Furthermore, a CARS image in the field of view 150×60µm² of polystyrene at the Raman shift of 3041cm^-1 has also been achieved. The results show the feasibility of our passively synchronized dual-color fiber laser to be employed as a stable and low-cost ultrafast laser source for CARS.