A coil arrangement is described for an implantable medical system. A coil winding has a planar ring shape winding that encloses a coil interior area. The coil winding is adapted for placement parallel to a corresponding partner coil for communication of an implant link signal having an associated magnetic field component characterized by a coupling factor k representing fractional amount of magnetic field coupling between the coils. A coil coupling lens of magnetic conductive material has multiple lens surfaces and is adapted to shape the magnetic field component to increase the coupling factor and minimize self-heating of adjacent tissues due to the magnetic field component. The lens surfaces include: i. an inner lens surface lying substantially parallel to the plane of the ring shape winding and having an inner lens surface perimeter enclosed within the coil interior area, ii. an outer lens surface lying substantially parallel to the inner lens surface and having an outer lens surface perimeter greater than the inner lens surface perimeter, and iii. at least one lens connecting surface connecting the inner lens surface perimeter and the outer lens surface perimeter.
