Femtosecond lasers have the unique propertity that the interaction of the pulses with matter can occur with no heating as the pulse length is shorter than the electron-phonon coupling time and so no heat transport is possible. This makes it possible to ablate the surface of materials with no thermal or other forms of damage, ideal for preserving heritage objetcs or cleaning/restoring structures under consderable service stresses.The recent advent of femtosecond lasers with up to kilowatt power levels now makes this process practical in industrial environments, for example recent tests suggest that a 1kW femtosecond source can ablate ~200 cubic mm/min of steel and ~35000 cubic mm/min of some types of paint.
The project addresses developing an efficient and effective process to ablate paint, contamination, and rust from the surfaces of the Sydney Harbour Bridge. Comparison with nanosecond laser pulses is planned, and collaboration with Transport for NSW, The University of Sydney, and the Australian Nuclear Safety and Technology Organisation will demonstrate that the process does no damage and does not compromise the fatigue strength and service life of the bridge. Field trials are an expected outcome fo this project.