The demand for and usage of broadband coherent mid-infrared sources,such as those provided by synchrotron facilities,are growing.Since most organic molecules exhibit characteristic vibrational modes in the wavelength range between 500 and 4000 cm-1,such broadband coherent sources enable micro-or even nano-spectroscopic applications at or below the diffraction limit with a high signal-to-noise ratio1-3.These techniques have been applied in diverse fields ranging from life sciences,material analysis,and time-resolved spectroscopy.Here we demonstrate a broadband,coherent and intrinsically carrier-envelope-phase-stable source with a spectrum spanning from 500 to 2250 cm-1 (-30 dB) at an average power of 24 mW and a repetition rate of 77 MHz.This performance is enabled by the first mode-locked thin-disk oscillator operating at 2μm wavelength,providing a tenfold increase in average power over femtosecond oscillators previously demonstrated in this wavelength range4.Multi-octave spectral coverage from this compact and power-scalable system opens up a range of time-and frequency-domain spectroscopic applications.