An optical chip is a planar component in which a light signal is guided by optical waveguides and in which light can be processed in various ways and for various purposes. Examples are splitting a light beam into its separate wavelengths, absorption of the light for sensor applications, modulating a high-content data signal onto a light beam, etc., all offering the possibility for cheaper and better optical systems. In these chips often connections occur between waveguides with different widths. Traditionally these connections are realized by long coupling sections having a linear or parabolic shape when viewed from above. If we want to shorten these coupling sections to gain precious chip surface area, innovative shapes should be applied. A general shape for an innovative coupler is proposed in this work and is optimized in various ways leading to a good coupling efficiency. In these simulations an in-house eigenmode expansion method, CAMFR, is used both for two- and three-dimensional waveguide calculations. At the optimization side, a successive line minimization and a standard genetic algorithm are successfully applied. Different initial assumptions for the shapes of these couplers can, after optimization, lead to similar structures, confirming the value of the applied methods. After simulation, a selection of optimized structures is realized in the material system silicon-on-insulator. For this manufacturing, standard deep-UV lithography with an illumination wavelength of 248 nm, normally used in the creation of CMOS chips, is applied. Optical measurements on these optical coupling structures confirm the calculated coupling efficiencies and lead us to the conclusion that couplers between planar optical waveguides with a different width can be shortened if, instead of the conventional linear or parabolic shapes, more complex structures are applied
