Experimental Research on Drilling and Cutting Urban Hedge Branches Using Multi-Wavelength Lasers

Although lasers are widely used in various industries, including aviation, healthcare, and communication engineering, there has been little research concentrated on the field of horticulture. In this paper, five semiconductor pumped fiber-coupled lasers emitting laser pulses of different wavelengths (450 nm, 532 nm, 808 nm, 915 nm, and 1064 nm) were used in the experimental drilling and cutting of hedge branches. A drilling effect on the hedge branches as a function of the laser power density, incident angle, and defocus condition was demonstrated, and it was found that a laser with a central wavelength of 450 nm had the lowest drilling power density and the shortest drilling-through time. It also enables the maximum tolerance of changes to the incident angle. The reason is closely related to the different absorption coefficients of lasers of various wavelengths on the hedge branches. In the cutting experiment, a laser at a wavelength of 450 nm was used, and the scanning speed of the laser was optimized. Good cutting effects were found at laser scanning speeds ranging from 18 mm/s to 23 mm/s. The layer of carbide formed by cutting the hedge branches can effectively block the invasion of bacteria, which is the advantage of using laser cutting in the field of horticulture.