Multi-gain interferometric laser for intra-cavity beam combining

The laser, whose name stands for Light Amplification by Stimulated Emission of Radiation, in less than a century has became a fundamental tool in several applications and technological processes, such as metrology, telecommunications, medicine and industry, because of their peculiar properties. More in details, they are spatially and temporally coherent, they exhibit a low divergence and can offer high power density and monochromaticity. The work of this thesis can be placed within the framework of laser assisted industrial processes. Material processing exploits the interaction between a high power laser beam and the matter. The interaction happens in the surface of the material where the extreme heat transferred by the laser source can cause a local phase change, without affecting in a significant way the bulk properties of the treated medium. Typically high brightness laser sources are used. The most used solution is represented by fiber lasers. In the last years the research moved towards the semiconductor laser sources because of the numerous advantages that they o↵er with respects to the other types of sources, like a higher conversion efficiency, a smaller size and the possibility of a mass production. Nevertheless, the maximum output power that can be extracted from a single diode laser is relatively small. The adopted strategies for power scaling rely on beam combining. Here we propose a novel architecture for the implementation of passive coherent beam combining, into a single resonant cavity. The main block of the scheme is an Interferometric Semiconductor Amplifier (ISA). In an ISA, the optical amplifier is placed in one arm of a Mach-Zehnder Interferometer. A sequence of ISA, placed into a common resonant cavity, is used for the power scaling. The theoretical model is presented, and the experimental results are discussed.