Abstract
Solid high-harmonic generation (sHHG) is a compact method for producing deep-ultraviolet and vacuum-ultraviolet (VUV) radiation at wavelengths near or below 200 nm. Generally, sHHG relies on ultrashort laser pulses (10–50 fs) at modest repetition rates (kHz) for sub-10 W average power. Here, we demonstrate VUV generation driven by a 50 W, turnkey, MHz-repetition-rate Yb-fiber laser with a pulse duration of ∼0.5 ps. We investigate the optimum material based on the detected 5th harmonic (H5 = 206 nm) flux with a 1.25 MHz driver, and find the following order:
α
-SiO
2
> MgO >
α
-Al
2
O
3
> ZnO > CaF
2
. However, at an average power of 50 W, MgO performs best, yielding an H5 photon flux of ∼10
10
photons/s. The most stable high-power operation was at 20 W, with an H5 and H7 flux of 7.1 × 10
9
and 5.2 × 10
8
photons/s, and RMS fluctuations of 0.80% and 1.14%, respectively.