Novel cover-layer-incident dual-layer near-field recording optics using hemispherical solid-immersion-lens

A novel for the design optics for using cover layer-incident dual-layer near-field recording (NFR) is proposed. Using two aplanatic positions of a hemispherical solid immersion lens (HMS), dual-layer NFR optics is designed and optimized. To achieve a high system numerical aperture (NA) of 1.45 for the dual recording layers, a prefocusing lens having NA of 0.7 and a solid immersion lens (SIL) with a refractive index of 2.086 are used. Critical spherical aberrations caused by variations in thickness and chromatic aberrations are effectively suppressed by zoom optics, an additional aspheric lens surface, and a diffractive optical element (DOE). The gap-induced aberration of the designed NFR optics is also investigated.