Design of Cover-Layer-Incident Dual Layer Near-Field Recording Optics Using Elliptical Solid Immersion Lens

Abstract

We propose the design of novel optics for media within a dual-layer near-field recording (NFR) device using an elliptical solid immersion lens (E-SIL). E-SIL-based near-field optics is designed for cover-layer-incident dual focus positions with a high numerical aperture of 1.4 in the region around λ= 405 nm. In this design, to improve the small optical tolerance for each imaging position and to insure the ability to fabricate the device, an additional aspheric lens surface is added on top of the hemispheric lens, and it is combined with zoom optics which are composed of two single lenses. To compensate for serious chromatic aberrations which happen seriously in optics using blue laser diodes, a diffractive optical element (DOE) is used. Using zoom optics, an additional aspheric lens surface, and DOEs together, wavefront aberration is effectively reduced over a broad range of variation in cover layer thickness and wavelength. In addition, in this study, an air-gap-induced aberration in the designed NFR optics is briefly observed.

Opto-Mechatronics Issues in Solid Immersion Lens-Based Near Field Recording

“…The chromatic aberration can be reduced by use of the DOE. Because Abbe's number of the DOE has the opposite sign of the general refractive optics [7]. There are some considerations for the design of the DOE.…”

Optical Design for the Optimum Solid Immersion Lens with High Numerical Aperture and Large Tolerance

“…In order to achieve the favorable optical performances, the new idea to improve the system tolerances is needed. [4][5][6] In a recent paper, Zhang introduced an idea based on the not aberration free but stable point of the spherical aberration curve according to the SIL thrust, 7) showing that the tolerance performances in the new system are better than the traditional aplantic SIL systems (same as hemi-and hyper-SIL) when applied to the multilayer two photon data read out system.…”