Mid-infrared optical combs from a compact amplified Er-doped fiber oscillator.

By means of a difference-frequency-generation (DFG) process driven by a two-branch Er-doped fiber laser at a stabilized 100 MHz repetition rate, broadly tunable pulses from 5 to 12 microm are generated with an unprecedented power level of around 100 microW. The mid-IR pulse train is expected to exhibit an harmonic comb structure as a result of the cancellation of the carrier-envelope offset frequency resulting from the DFG process.