Percussion Nd:YAG Laser-incision of Radiata Pine: Effects of Laser Processing Parameters and Wood Anatomy

Laser-incision is gaining recognition in the timber processing industry as a preferred and competitive technique for increasing uptake of chemical and preservative treatments. This work details percussion Nd:YAG laser-incision of Radiata Pine, conducted at different wavelengths, incident laser energies and focal point positions. For the first time, the effect of wood anatomy (latewood and earlywood tissues) on the efficiency and quality of Nd:YAG laser-incision of Radiata Pine is explored. Nd:YAG laser wavelengths of 1064 nm (fundamental wavelength), 532 nm (second harmonic) and 355 nm (third harmonic) were used to understand their effect on laser-incised hole characteristics. A maximum laser-incised hole diameter of ~ 2.5 mm was measured at 1064 nm for 700 pulses. The presence of earlywood and latewood had a distinct effect on hole shape evolution, showing the importance of wood anatomy in the process of percussion Nd:YAG laser-incision. Ultra-violet (UV) radiation (355 nm) was the preferred wavelength for laser-incision of Radiata Pine as it gave rise to less carbonisation, less tapering and a uniform incision along the length of the laser-incised holes. Maximum depth of the laser-incised hole was measured (~ 20 mm) using the 355 nm wavelength. Incident laser energy, wavelength and wood anatomy had a dominant role in laser-incision hole size, shape and quality. This demonstrates the critical effect of wood anatomy on the laser-incision process when considering and utilising laser technology to produce incisions for the wood treatment and wood preservation industries.