Intensity distribution conversion from Gaussian to Top-Hat in a single-mode fiber connector

Abstract: Gaussian to top-hat beam shaping is widely used today in areas of cutting, welding, and laser patterning. Typically, single-mode solid state lasers are used whose Gaussian intensity distribution is transformed into a top-hat. In this thesis the transformation is applied in a single-mode fiber connector, where the aim is a uniform intensity distribution of the emerging light from the connector. This is desirable in unclean environments where the probability of dirt or dust particles on the connector interface is high. Different methods of the transformation are analyzed, and the circular symmetric Powell lens is found most suited for implementation in a fiber connector. Two different connector-models where the Powell lens is involved are designed and for this purpose two optical simulation software products, FRED and ZEMAX, are used. These two products are compared concerning user friendliness, support, optimization feature, and accuracy of the simulations. The comparison is valid for the content of this thesis, but the scope of applications of these products reach far beyond this project. Because of the expensiveness in producing just one custom made lens, such as the circular symmetric Powell lens, instead cylindrical Powell lenses were used in the experiments, which are catalogue lenses. The experiments showed i.a. that the transformation predicted was successful. They also revealed some shortcomings in the simulation tools.