Fig. 1. Surface phase defects induced small-scale intensity modulation.

Fig. 2. Surface phase defects exist on the reflecting mirrors. These mirrors support lasers with beam size $360~\text{mm}\times 360~\text{mm}$.

Fig. 3. (a) Simulated laser intensity modulation before FOA and (b) the experimental result. The simulated and experimentally captured beam sizes are both $360~\text{mm}\times 360~\text{mm}$.

Fig. 4. $3{\it\omega}$ intensity modulation in the FOA. THG denotes three harmonic generations.

Fig. 5. Damage on the vacuum window after (a) 2.2 and (b) $3.1~\text{J}/\text{cm}^{2}$ ultraviolet operating fluences. The periphery frame indicates the laser-passing area of $360~\text{mm}\times 360~\text{mm}$.