Development of a laser beam modeling tool for high power applications

Amazing technological progresses have been made in the high-power laser field in the last few decades, thus allowing laser systems to be used in several applications, ranging from materials processing (cutting, marking, welding etc.) to biomedical and military sectors. Before the last decade, laser material processing was dominated by CO2 lasers. However, due to their very low wall plug efficiency (amount of electrical power converted into optical) and mechanical reliability issues, CO2 lasers have been replaced by fiber lasers, which are pumped by high power laser diodes (HPLDs). HPLDs are characterized by compactness, high efficiency, high reliability and low ownership costs. Since 2017, the HPLDs became the leading market sector for lasers. The state of the art of the single emitting chips is around 10 W; in order to obtain kilowatt range sources, different beam combining techniques are employed. The thesis purpose is the development of a versatile tool to design devices based on the beam stacking of single emitters with applications to high-power laser modules and beam shaping components. The model is based on Ray Tracing Technique and Gaussian beams and has been verified by comparing the results with measurements obtained from ad hoc experimental benches. The developed software is able to realize a laser module with a variable number of chips and to assemble them in the desired structure (array, rectangle, circle, etc.) by selecting the positions where to locate the diodes. It is also possible to modify the parameters of the chips, as the dimensions and the emission wavelength. Concerning the beam shaping applications, the effect of different optical elements aimed at material processing was studied. A ring-shaped beam, useful to obtain circular cutting profiles, was simulated by means of the tool; the action of a set of cylindrical lenses producing a laser line incident on the target material was instead verified in laboratory.