Mid-IR multiwavelength difference frequency generation based on fiber lasers.

A mid-IR multiwavelength difference frequency generation (DFG) laser source with fiber laser fundamental lights is demonstrated by using the dispersion property of PPLN to broaden the quasi-phase-matching (QPM) acceptance bandwidth (BW). Our results show that the QPM BW for the pump YDFL is much larger than that for the signal EDFL. Using a multiwavelength YDFL and a single-wavelength EDFL as the pump and the signal lights, the DFG laser source can simultaneously emit 14 mid-IR wavelengths with the spacing of 14 nm at a fixed PPLN temperature. Moreover, mid-IR multiwavelength lasing lines can be synchronously tuned between 3.28 and 3.47 microm.