Sol-gel processing of ZrO 2 and polymer doped-ZrO 2 monolayer reflective films with high laser damage threshold

A series of ZrO 2 and polymer doped-ZrO 2 sols have been synthesized by the controlled hydrolysis of zirconium n-propoxide. Acetic acid was used as the chelating agent. Poly(ethylene glycol)(PEG) 200 and polyvinylpyrrolidone(PVP) were introduced to produce the hybrid sols. ZrO 2 and the polymer doped-ZrO 2 optical thin films were then prepared by spin-coating the stable sols on K9 glass substrates. Effects of various synthetic parameters were studied, on the sol stability, the microstructure of colloidal system, the structural and optical properties of the films, as well as the laser damage resistance. In our reaction systems, both hydrolysis and chelation coexist. The preference for any of the two reactions strongly depends on the system composition and ultimately determines the stability and microstructure of the colloidal system. Besides, the addition of a proper amount of PEG200 and PVP, which probably acts as the competitive ligands, particle surface protective polymers and structure directive agents, can modify the hydrolysis-condensation process, thus producing more stable, uniform sols with mass fractal structure (f m =2.33—2.46) and average particle diameter of 19.1—23.7nm. Benefiting from the precursor sol structure, the polymer doped-films exhibit excellent surface planarity and uniform inner structure, which endows the films with good optical property and excellent laser damage resistance. For instance, the hybrid film with 10% PEG200 and 15% PVP (mass fractions) showed a high laser damage threshold of 24.5J/cm 2 (for 1ns pulse duration) and a reflectivity increase of about 2% than that of the substrate at wavelength of about 1000nm.