Ultra-broadband pulse generation via hollow-core fiber compression and frequency doubling for ultra-intense lasers

We demonstrate an ultra-broadband few-cycle high temporal contrast infrared laser source based on cascaded OPA, HCF and SHG processes. In this setup, the spectrum of ~1.8 µm laser pulse is with near 1 µm full bandwidth by employing an argon gas-filled HCF. Subsequently, after frequency doubling with cascaded crystals and dispersion compensation by a fused silica wedge pair, 9.6 fs (~3 cycles) and 150 µJ pulses centered at 910 nm with full bandwidth of over 300 nm can be generated. The energy stability of the output laser pulse is excellent with 0.8% (RMS) over 20 mins, and the temporal contrast is >1012 before the main pulse. The excellent temporal and spatial characteristics and stability make this laser to be used as a good seed source for ultra-intense and ultrafast laser systems.