Ultrahigh-Speed Coherent Anti-Stokes Raman Spectroscopy with a Hybrid Dual-Comb Source

Coherentanti-Stokes Raman scattering (CARS) spectroscopy withtime-delayed ultrashort pulses and a single-pixel photodetector hasshown great potential for spectroscopic imaging and transient studiesin chemistry and biological research. However, those systems relyon mechanical delay lines or two asynchronous optical combs with inflexiblerepetition frequencies, technically limiting their acquisition speeds.Here, we demonstrate a hybrid dual-comb CARS system involving a broadbandfiber laser and a highly flexible, frequency-modulated electro-opticcomb. We achieve multiplex CARS spectra (2800-3200 cm(-1)) with a moderate resolution (30 cm(-1)) at a maximumrefresh rate of 1 MHz, limited by the radio frequency synthesizerwe use. Fast spectroscopic CARS imaging is demonstrated for liquidmixtures. Our system enables spectral measurements in the high-wavenumberC-H stretching region at a record speed that is an order ofmagnitude higher than that of state-of-the-art systems, which mayopen up new opportunities for fast chemical sensing and imaging.