Sensored Handheld Fiber-Optic Delivery System for Controlled Laser Ablation

Fluence (J/cm²) and reflectance are key parameters in pulsed laser ablation processes. The dynamics and rate of the material removal are strictly dependent on the energy dissipated into the material under irradiation, which is complementary to the reflected energy. Laser cleaning of artifacts of cultural interest is a well-known application of laser ablation, which significantly grew along the last decade. The Long Q-Switch Nd:YAG laser (1,064 nm, τ=120 ns) is one of the most used laser systems (Salimbeni et al., J Cult Herit 4(1):72–76, 2003; Cacciari et al. Chem 402(4):1585–1591, 2012; Siano et al., Appl Phys A 106(2):419–446, 2012). This is usually equipped with optical fiber beam delivery terminated with a handpiece including an imaging lens and a mechanical arrangement to vary the fiber-to-lens distance in order to suitably set the laser spot diameter at the target. In this way, skilled restorers can set the operating fluence according to the interaction phenomenology observed. Here, a novel laser handpiece equipped with optical sensors in order to monitor fluence at the target and its reflectance, as well as the optimum working distance, is presented.