High-sensitivity frequency modulation CARS with a compact and fast tunable fiber-based light source

Frequency modulation coherent anti-Stokes Raman scattering (FM CARS) is presented, using a compact as well fast and widely tunable fiber-based light source. With this source resonances between 700 cm$^{-1}$ 3200 can be addressed via wavelength tuning within only 5 ms, which allows for FM CARS measurements with frame-to-frame switching. Moreover, the functionality high-sensitivity was integrated by means of fiber optics to keep stable reliable operation. The accomplished 40 times enhanced sensitivity at lock-in amplifier (LIA) bandwidth 1 Hz. For imaging switching LIA MHz 18-fold contrast enhancement could verified, making ideal routine out-of-lab medical diagnostics or environmental sensing.