THE OPTICAL DESIGN FOR NEAR FIELD OPTICAL APPROACH USING SOLID IMMERSION LENS FOR HIGH DENSITY RECORDING

The SIL (Solid Immersion Lens) Optical System which attracting attention as future high-density recording, focuses a laser beam to the disk surface without any substrate. We have studied the possibility of compatibility of the SIL optical system with the conventional optical disk system which focuses laser beam through a substrate. It was found that the compatibility with optical disks having 0.6 mm thick substrate can be obtained by setting the SIL refractive index to 1.8, radius to 500 μ m, and SIL height to 708 μ m. Although the dimensional accuracy is very severe in this construction, however, it can obtain a spot with very small aberration for both optical disks for SIL and conventional optical disks by loading/unloading SIL.