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

Abstract

We demonstrate the single-step generation of mid-infrared femtosecond laser pulses in a AgGaSe₂ optical parametric oscillator that is synchronously pumped by a 100MHz repetition rate sub-90fs erbium fiber laser. The tuning range of the idler beam in principle covers ∼3.5 to 17μm, only dependent on the choice of cavity and mirror design. As an example, we experimentally demonstrate idler pulse generation from 4.8 to 6.0μm optimized for selective vibrational resonant molecular spectroscopy. We find an oscillation threshold as low as 150mW of pump power. At 300mW pump power and a central wavelength of ∼5.0 μm, we achieve an average infrared power of up to 17.5mW, 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 1h.