Widely tunable picosecond and subpicosecond pulses in the mid-infrared by parametric three-photon interaction

We demonstrate that synchronous pumping of singly resonant, optical parametric oscillator with sequences of a few hundred pulses yields intense, tunable pulses in a large spectral range with high spatial and temporal quality. The OPO pulses are converted to the mid-infrared by subsequent difference frequency generation with simultaneous amplification. Two schemes are discussed: (i) Generation of intense, bandwidth-limited pulses of 1 .5 ps in the range 1 .2 - 1.9 μm. using the second harmonic of a feedback controlled Nd:YLF laser as a pump source. Subsequent down-conversion yields 2 ps pulses of 20 μJ energy in the wavelength range 2.3 to 4.2 m. (ii) Tunable fs pulses in the IR; starting from the second harmonic of a feedback-controlled Nd:glass laser we obtain pulses at 0.7 to 1.8 μm with 200 fs duration. Subsequent down conversion of the OPO emission in AgGaS2 results in widely tunable subpicosecond pulses in the range 3.3 to 10 m. A duration of 0.7 ps is measured for the pulses with energies of 2 μJ.