Abstract

Currently, data recording density in cover-layer-protected near-field-recording (NFR) and multiple-recording layered NFR optical data storage technology is limited by the difficulty in obtaining high-refractive-index cover layer materials. In addition, with the exception of improved resolution, the higher the numerical aperture (NA), the poorer the optical characteristics. However, in this study, we present novel cover-layer-protected solid immersion lens (SIL)-based NFR optics that provide superior optical performance with higher recording density, greatly enhanced focal depth, and less sensitivity to near-field air-gap-distance variation by modulating the amplitude and phase in the entrance pupil using annular pupil zones. Using an annular aperture consisting of three concentric annular zones to effect amplitude and phase modulation, the 1.45NA cover-layer-protected SIL-based NFR optics achieved a data recording density as high as that of conventional 1.80NA SIL-based NFR optics. These 1.45NA optics yielded a full-width at half-maximum (FWHM) spot size of 0.315λ, a focal depth of 0.82λ, a focused beam spot sensitivity to air-gap-distance within the near-field region of 0.04λ, and a sidelobe intensity lower than 7%. In comparison with conventional 1.80NA SIL-based NFR optics, the annular aperture optics achieved 3.5 times longer focal depth and much lower focused beam spot sensitivity to air-gap distance while maintaining the same high resolution. The introduction of this novel specially designed NFR optics could greatly improve data capacity in multiple-recording layered NFR.

© 2009 Optical Society of America

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