Mid-infrared frequency comb based on highly-efficient optical parametric oscillator

We present the development of a mid-infrared (IR) frequency comb based on a singly-resonant optical parametric oscillator (OPO) for signal. An average idler output power of 110mW was achieved at the idler wavelength of 3.5 μm by pumping with a 1040nm ytterbium-fiber mode-locked laser with 2.2W output power. The OPO-based mid-IR comb can be applied to the generation of a high-power, high-repetition-rate far-IR comb, which will be essential for precision molecular spectroscopy as well as frequency metrology in the far-IR region.