Simplified and improved heterodyne coherent anti-Stokes Raman scattering for background correction

Heterodyne coherent anti-Stokes Raman scattering is presented with a single and compact fiber-based light source only, providing the pump and Stokes as well as local oscillator pulses with a fixed phase relation. The interferometrically superimposed pulses of the CARS signal and the local oscillator generated heterodyne gain, scaling with the LO power, and amplifying the weak CARS signal at the detection site. The functionality of this heterodyne CARS setup was verified by measurements of the heterodyne amplification, the sample concentration, and the phase dependence of the signal. Additionally, 10-fold suppression of non-resonant signal was achieved for background correction.