A Variable Pulsewidth Nd:YAG Laser System for Conservation

Photoablation is a physical process employed for the cleaning of artefacts. While several authors have reported investigations concerning the dependence of the effects induced on the material for different laser wavelengths, no similar investigations have been reported so far about the dependence on the pulse duration, in spite of its importance being recognised. In order to approach this issue and to optimise the interaction process on different materials, a new Q-switched Nd:YAG laser system with variable pulse width for cleaning applications was designed and built at the Quantum Electronics Institute in Florence. It provides an extended pulse duration in respect of the standard Q-switched regime, by means of interchangeable optical fibers in the resonator. The new laser allows to change the pulse duration in the range between tens and hundreds nanoseconds up to several microseconds. According to our experience the adjustment of the pulse duration in this range may avoid the possibility of strong mechanical forces and excessive heating in the substrate, as it has been observed with standard Nd:YAG laser systems. The laser may be proposed for an accurate cleaning in a variety of restoration problems and materials.