Optical coupling and mode-selective separation or superposition of optical fields

An arrangement for optical coupling and for mode-selective separation or superposition of optical fields, comprising

• a waveguide-based optical coupling element having at least three optical coupling points, the waveguide-based optical coupling element comprising a core region and a cladding region adjoining the core region, a refractive index difference of at least 0.05 occurring between the core region and the cladding region, the waveguide-based optical coupling element being designed in the form of a three-dimensional free-form structure, wherein along a portion of the waveguide-based optical coupling element corresponding to a transition region between the at least three optical coupling points, a centerline of the transition region exhibits a non-zero torsion, and a cross-section of the transition region undergoes a continuous deformation characterized by a monotonic rotation or morphing of a principal confinement axis about the centerline,
• at least one first optical coupling point having at least two differing guided eigenmodes assigned to the first optical coupling point,
• at least one second optical coupling point having at least one guided eigenmode assigned to the second optical coupling point, and
• at least one third optical coupling point having at least one guided eigenmode assigned to the third optical coupling point,
• at least one optical component part which has at least one further optical coupling point;
• wherein at least one of the optical coupling points of the waveguide-based optical coupling element is optically connected to the at least one further optical coupling point of the optical component part, and
• wherein the waveguide-based optical coupling element is configured to efficiently bidirectionally transfer light
• between at least one first guided eigenmode assigned to the first optical coupling point and the at least one guided eigenmode assigned to the second optical coupling point and
• between at least one second guided eigenmode assigned to the first optical coupling point and the at least one guided eigenmode assigned to the third optical coupling point;
• and
• wherein the waveguide-based optical coupling element is configured to separate the at least two guided eigenmodes assigned to the first optical coupling point into different polarizations and to subsequently rotate one direction of the polarizations of the separated eigenmodes in order to facilitate an alignment of the directions of the polarizations to the at least one guided eigenmode assigned to the second optical coupling point and to the guided eigenmode assigned to the at least one third optical coupling point.