This paper describes development of a bi-axial actuator-based air gap servo system for a near field optical recording system using a blue laser and a solid immersion lens (SIL). We first present a new pull-in procedure ensuring smooth air gap servo start-up without lens-disc collision. Furthermore, a memory-loop control technique has been employed to realize a high-speed air gap servo system guaranteeing a high data transfer rate.

Recent demonstrations have shown that near-field optical recording with a solid immersion lens in a conventional actuator is a strong candidate for optical storage beyond Blu-ray Disc. All results published so far were obtained with so-called first-surface configurations, in which the data layer is not protected by a cover-layer. In this paper we demonstrate a next step towards creating a system suitable for a commercial product with removable discs. First results are presented for read-out of discs with a few µm protective polymer cover-layer and a solid immersion lens with NA=1.45 and λ=405 nm.

We present a single-wavelength near field recording set-up with a blue laser and a NA=1.9 solid immersion lens in a conventional focus and tracking actuator. The most important aspects to realize such a near field recording system are discussed, in particular, gap error signal normalization and correction of chromatic aberration of the objective lens. First recording results demonstrate that the set-up is fully operational.

We present the status of our efforts to demonstrate the feasibility of recording on a cover-layer protected dual-layer optical disc with a blue laser and NA=1.45 objective lens that is based on a solid immersion lens (SIL). We discuss the potential data density and some practical and theoretical considerations for the light path, the objective lens and the media. In particular, we show a lens design and results of prototype manufacturing for a NA=1.45 lens that focuses on the data layer of an optical disc through a sub-wavelength air gap and a 3 µm spin coated cover-layer that protects the data on the disc.