Increased Laser-Damage Resistance of Sol.pdfVIP

Increased Laser-Damage Resistance of Sol?Gel Silica Coating by Structure Modification Xiaoguang Li,?,? Mark Gross,? Bob Oreb,? and Jun Shen*,? ?Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Tongji University, Shanghai, China ?CSIRO Australian Centre for Precision Optics, Sydney, Australia ABSTRACT: Sol?gel silica coatings prepared for high-power laser applications were optimized by a two-step structure modification through treatment of the sol with poly(ethylene glycol) (PEG), followed by treatment of the coating with ammonia. The effect of each treatment on the laser-induced damage threshold (LIDT) at 1064 nm wavelength was studied, mainly in terms of the change in the coating’s structure. Both of these treatments increased the LIDT, and the greatest LIDT was achieved by combining the two treatments. The LIDT increase can be attributed to the decrease in structural defects such as nodular defect and the variety of pore-distribution, resulting from PEG and ammonia treatments, respectively. The procedure of producing coated glass with high LIDT for 1064 nm laser irradiation was suggested, involving substrate etching, sol modification, and coating treatment. ■ INTRODUCTION High-power laser systems, such as those at NIF, LMJ, and SG- 3, are the core devices in inertial confinement fusion (ICF) research. The maximum output power available from these systems is decisive to their success but is typically limited by laser-induced optical damage. Sol?gel silica coatings have been well-studied and applied to the transmissive optical compo- nents in high-power laser systems for their antireflection (AR) properties and high LIDT.1?10 This kind of coating is a product of silica sol prepared using the Sto?ber process,11 in which silicon alkoxides hydrolyze and condense in alcohol solvents in the presence of water and a catalyst (e.g., NH3). Silica particles and clusters are formed and extend to a network in the aged sol, thus giving rise