Broadly tunable femtosecond mid-infrared source based on dual photonic crystal fibers

We report a novel scheme of generating broadly tunable femtosecond mid-IR pulses based on difference frequency mixing the outputs from dual photonic crystal fibers (PCF). With a 1.3 W, 1035 nm, 300 fs and 40 MHz Yb fiber chirped pulse amplifier as the laser source, a PCF with single zero dispersion wavelength (ZDW) at the laser wavelength is employed to spectrally broaden a portion of the laser pulses. Facilitated by self-phase modulation, its output spectrum possesses two dominant outermost peaks that can be extended to 970 nm and 1092 nm. A different PCF with two closely spaced ZDWs around the laser wavelength is used to generate the intense Stokes pulses between 1240 - 1260 nm. Frequency mixing the dual PCFs outputs in an AgGaS2 crystal results in mid-IR pulses broadly tunable from 4.2 mu m to 9 mu m with a maximum average power of 640 mu W at 4.5 mu m, corresponding to 16 pJ of pulse energy. (C) 2013 Optical Society of America