CW-Seeded Parametric Combs with Sub-100 Mrad Carrier-Envelope Phase Noise

Frequency metrology with optical comb sources heavily relies on mode-locked fiber lasers. However, suitable fiber lasers only exist for two wavelength bands around 1.03 and 1.55 μm, and nonlinear conversion mechanisms have to be employed to access out-of-band wavelengths. To this end, parametric amplification appears appealing as it allows for high conversion efficiency. Nevertheless, optical parametric amplifiers (OPAs) require coherent seed light at the signal wavelength, and this seed light has to be deduced from the pump light by spectral broadening in highly nonlinear optical fibers, which can easily destroy favorable coherence properties. Here we demonstrate an alternative approach, using a single-frequency seed laser with 8 mW output power. Despite limited seed power, surprisingly low carrier-envelope phase (CEP) jitters of only 82 mrad result.