High numerical aperture optical focusing device for use in data storage systems

A near-field optical or MO data storage system uses an optical focusing device for focusing an incident optical beam to a small size focal spot. The optical focusing device includes an optically transmissive body which is defined by a generally flat incident surface, a flat, bottom surface disposed opposite and parallel to the incident surface, and a reflective side coated with a reflective layer for reflecting the optical beam through the body toward the bottom surface. The bottom surface defines a focal plane on which the focal spot is formed, for generating a localized evanescent field. The focal spot is located along a central axis P, in very close proximity to the data storage disk, such that the localized evanescent field interacts with the disk, for enabling data to be transduced to and from the disk by effecting near field coupling. An electro-magnetic coil or coil assembly, can optionally be formed on the bottom surface, co-axially with the focal spot, for generating a desired write magnetic field. The reflective side of the optical focusing device preferably has a parabola shaped curvature, but other shapes can alternatively be selected. For example, the side curvature can have a tilted parabola shape.