Ferry Zijp

Development of an air gap servo system for high data transfer rate near field optical recording

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.

Near-field read-out of a 50-GB first-surface disc with NA=1.9 and a proposal for a cover-layer-incident, dual-layer near-field system

We present read-out results of a 50 GB disk with a blue laser and a NA=1.9 Solid Immersion Lens in a conventional focus and tracking actuator. Furthermore, we show a light path and a disk design that enable cover-layer incident near field recording on dual-layer disks with a capacity of 300 GB on a double-sided disk.

High-density near-field optical recording with a solid immersion lens, conventional actuator, and a robust air gap servo

We present a near-field optical recording system with a solid immersion lens (SIL) in a conventional biaxial actuator. We manufactured a super-hemispherical aplanatic SIL with a numerical aperture (NA) of NA = 1.9. Our system utilizes a gap error signal (GES) and a digital servo system to drive a conventional actuator in order to maintain a constant air gap of 25 nm between the SIL and a spinning optical disc.

Near-Field Recording with a Solid Immersion Lens on Polymer Cover-layer Protected Discs

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.

Towards a Multi-Layer Near-Field Recording System: Dual-Layer Recording Results

We advocate the use of a polymeric cover layer for protecting the data layer and the tip of the solid immersion lens in near-field optical recording system. With a cover on top of the data layer, the numerical aperture (NA) of the objective lens is limited to the refractive index of the cover material. This means that the maximum attainable NA of cover-incident near-field systems and therefore the maximum achievable storage density is lower compared to that for first surface systems. This lower storage capacity per layer can be more than compensated for by using multiple data layers which is not possible in first-surface systems with bare discs. In this paper we present first experimental results for near-field recording with a solid immersion lens that focuses through a cover layer and a spacer layer onto a data layer, as in a dual-layer near-field disc.

High Numerical Aperture Optical Recording : Active Tilt Correction or Thin Cover Layer?

Playback of a 12 cm diameter replicated ROM disc with a 0.6 mm substrate thickness and a storage capacity of 10 GB has been achieved using a light path with a dual-lens objective with NA=0.85 and active tilt control. The disc tilt margin exceeds ±0.7 degree. Also backward compatibility with digital versatile disc (DVD) has been demonstrated. Active tilt correction is not required for read out of a disc with a 0.1 mm transparent cover layer. This technique has also been studied experimentally. The merits and disadvantages of the two approaches are discussed.

Near Field Recording on First-Surface Write-Once Media with a NA=1.9 Solid Immersion Lens

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.

Improved Near-Field Recording System for First-Surface Media with an NA=1.9 Solid Immersion Lens

Near-field optical recording using a solid immersion lens is quickly becoming an attractive technology for use in commercial optical data drives. Calculations and experiments show that Near-field optical recording has the potential to enable data storage capacities of more than 150 GB per side on a compact disc (CD)-sized disc, which may prove sufficient to continue the optical recording roadmap beyond Blu-ray Disc. Compared to alternative approaches that aim to achieve high storage densities, near-field recording requires a minimum change in drive architecture and media technology. In this paper we present our progress on the development of a near-field optical recording system with an NA=1.9 Solid Immersion Lens in a conventional actuator, using a single blue laser diode.

High data transfer rate near-field recording system with a solid immersion lens for polymer cover-layer discs

We present our progress on the development of a single-wavelength near-field recording system with a blue-violet laser and a NA=1.45 Solid Immersion Lens in a conventional 3D actuator. We will introduce our near-field optical recorder and present good recording results achieved on discs with a 3 μm thick spin-coated protective polymer cover-layer using a channel bit length of 43.7 nm. Furthermore, we will show recent results on high-speed near-field readout, up to 3xBD speeds, through a cover-layer using feed-forward control in the air gap servo system.

Effects of Polarization on Wave Front Measurements and Manufacturing of Solid Immersion Lenses for Near-Field Optical Recording

Near-field optical recording with a solid immersion lens (SIL) is a promising and logical technology for commercial optical data drives with data storage densities beyond that of Blu-ray Disc. In many aspects the technology of near-field recording with a SIL is very similar to conventional optical recording, however for lenses with a numerical aperture (NA) exceeding unity certain optical effects occur that do not play a role in conventional optical recording systems. An example of one such effect that we found in practice is a polarization induced spurious wave front aberration. In this paper we report on the analysis and correction of those polarization induced spurious wave front aberrations in NA>1 Solid Immersion Lenses and in particular for the NA=1.9 lenses used in our experimental near-field optical recorder.