Holmium-doped fiber amplifier for pumping a ZnGeP₂ optical parametric oscillator

We present a holmium-doped all-fiber master oscillator power amplifier (MOPA) system operating at 2108 nm targeting optical frequency conversion applications. The MOPA delivers pulses of 0.52 mJ energy 10 kHz repetition rate after three amplification stages, with close to square-shaped temporal profile 50 ns duration, diffraction-limited beam quality and linear polarization. Challenges achieving high gain efficiency in the final stage are discussed attributed quenching effects inferred from measurements non-saturable absorption holmium fibers. Using this MOPA, we demonstrate mid-IR 59% by direct pumping ZnGeP 2 parametric oscillator.