Compact, ultrastable, high repetition-rate 2 µm and 3 µm fiber laser for seeding mid-IR OPCPA.

ABSTRACT

We report a compact and reliable ultrafast fiber laser system optimized for seeding a high energy, 2 µm pumped, 3 µm wavelength optical parametric chirped pulse amplification to drive soft X-ray high harmonics. The system delivers 100 MHz narrowband 2 µm pulses with >1 nJ energy, synchronized with ultra-broadband optical pulses with a ∼1 µm FWHM spectrum centered at 3 µm with 39 pJ pulse energy. The 2 µm and 3 µm pulses are derived from a single 1.5 µm fiber oscillator, fully fiber integrated with free-space downconversion for the 3 µm. The system operates hands-off with power instabilities <0.2% over extended periods of time.