Upper temperature limit for nanograting survival in oxide glasses

The thermal stability of self-assembled porous nanogratings inscribed by an infrared femtosecond (fs) laser in five commercial glasses (BK7, soda lime, 7059, AF32, and Eagle XG) is monitored using step isochronal annealing experiments. Their erasure, ascertained by retardance measurements and attributed to the collapse of nanopores, is well predicted from the Rayleigh-Plesset (R-P) equation. This finding is thus employed to theoretically predict the erasure of nanogratings in the context of any time-temperature process (e.g., thermal annealing, laser irradiation process). For example, in silica glass (Suprasil CG) and using a simplified form of the R-P equation, nanogratings composed of 50 nm will erase within ∼30m i n, ∼1µs, and ∼30n s at temperatures of ∼1250^∘ C, 2675°C, and 3100°C, respectively. Such conclusions are expected to provide guidelines to imprint nanogratings in oxide glasses (for instance, in the choice of laser parameters) or to design appropriate thermal annealing protocols for temperature sensing.