Fig. 1. Preparation of ultra-BACs.

Fig. 2. Transmission spectra of ultra-BAC and N31^[20] Nd:glass absorption spectra (black curve).

Fig. 3. Variation of the transmission spectra with light incidence and N31 Nd:glass absorption spectra (black dashed curve). (a) BACs, (b) $\text{SiO}_{2}/\text{TiO}_{2}$ coatings and (c) uncoated fused silica glass.

Fig. 4. Particle diameter distribution by volume of sols (a) BA60 and (b) LA90.

Fig. 5. Transmittance of (a) BA60 and (b) LA90 before and after baking at $500\,^{\circ }\text{C}$.

Fig. 6. $\text{N}_{2}$ adsorption/desorption isotherm, and pore size distribution curve of LA90 after (a) $200\,^{\circ }\text{C}$ treatment and (b) $500\,^{\circ }\text{C}$ treatment.

Fig. 7. (a) Transmittance of the BAC before and after rubbing by the cotton ball immersed with ethanol 100 times. (b) Transmittance of the BAC before and after deionized water flushing.

Fig. 8. $857~\text{mm}\times 587$ mm amplifier blast shield with ultra-BAC spray cleaned with deionized water.