Yb-fiber-based, high-average-power, high-repetition-rate, picosecond source at 2.1 µm.

We report a high-repetition-rate picosecond fiber-based source at 2.1 µm offering exceptional performance capabilities over existing lasers near this wavelength, providing high average power and efficiency together with excellent spectral, power and beam pointing stability, in high spatial beam quality. This new source is based on a near-degenerate MgO:PPLN optical parametric oscillator (OPO) pumped by an Yb-fiber laser at 1064 nm, and incorporating a diffraction grating for spectral control. The device provides as much as 7.1 W of average power at 2.1 µm for a pump power of 18 W at an extraction efficiency of 39.4% in pulses of 20 ps at 79.3 MHz. The output exhibits passive power stability better than 1% rms over 15 hours, and a beam pointing stability ∼40 µrad over 1 hour, in high spatial quality with M2 ∼ 3.5. The output beam is linearly polarized and the pulse train has an amplitude stability better than 3.4% rms over 2 µsec. Radio-frequency measurements of the output pulse train also confirm high temporal stability and low timing jitter, indicating that the source is ideal for variety of applications including pumping long-wavelength mid-infrared OPOs. Photograph shows the temperature-controlled, 50-mm-long MgO:PPLN crystal inside the cavity, used as nonlinear gain medium in the picosecond source operating at 2.1 µm. The visible light is the result of non-phase-matched second harmonic generation of the pump beam in the MgO:PPLN crystal. [ABSTRACT FROM AUTHOR]