Single-step sub-200 fs mid-infrared generation from an optical parametric oscillator synchronously pumped by an erbium fiber laser

Reviews and Highlights	Quantum Science	Molecular and Soft-matter	Ultrafast Nano-optics and Nanophotonics	Mineralogy and Geochemistry

Bernd Metzger, Benjamin Pollard, Ingo Rimke, Edlef Büttner, and Markus B. Raschke
Optics Letters 41, 4383 (2016).
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We demonstrate the single-step generation of mid-infrared femtosecond laser pulses in a AgGaSe₂ optical parametric oscillator that is synchronously pumped by a 100 MHz repetition rate sub-90 fs erbium fiber laser. The tuning range of the idler beam in principle covers ∼3.5 to 17 μm, only dependent on the choice of cavity and mirror design. As an example, we experimentally demonstrate idler pulse generation from 4.8 to 6.0 μm optimized for selective vibrational resonant molecular spectroscopy. We find an oscillation threshold as low as 150 mW of pump power. At 300 mW pump power and a central wavelength of ∼5.0 μm, we achieve an average infrared power of up to 17.5 mW, with a photon conversion efficiency of ∼18%. A pulse duration of ∼180 fs is determined from a nonlinear cross-correlation with residual pump light. The single-step nonlinear conversion leads to a high power stability with <1% average power drift at <0.5% rms noise over 1 h.