说明：  We demonstrate a new approach to CARS spectroscopy by effi ciently syn- thesizing synchronized narrow-bandwidth (less than 10 cm− 1) pump and Stokes pulses (frequency diff erence continuously tunable upto ～3000 cm− 1) based on spectral compres- sion together with second harmonic generation (in periodically-poled nonlinear crystals) of femtosecond pulses emitted by a single compact Er-fi bre oscillator. For a far better signal to non-resonant background contrast, interferometric CARS (I-CARS) is demonstrated and CARS signal enhancement upto three orders of magnitude is achieved by construc- tive interference with an auxiliary local oscillator at anti-Stokes fi eld, also synthesized by spectral compression of pulses emitted the same fi bre oscillator.