Coen Adrianus Verschuren

Rapid integrated biosensor for multiplexed immunoassays based on actuated magnetic nanoparticles

The realization of biomolecular detection assays for diagnostic purposes is technologically very challenging because such tests demand full integration for ease of use and need to deliver a high analytical performance with cost-effective use of materials. In this article an optomagnetic immunoassay technology is described based on nanoparticles that are magnetically actuated and optically detected in a stationary sample fluid. The dynamic control of nanoparticles by magnetic fields impacts the key immunoassay process steps, giving unprecedented speed, assay control and seamless integration of the total test. The optical detection yields sensitive and multiplexed assays in a low-cost disposable cartridge. We demonstrate that the optomagnetic technology enables high-sensitivity one-step assays in blood serum/plasma and whole saliva. Drugs of abuse are detected at sub-nanogram per millilitre levels in a total assay time of 1 min, and the cardiac marker troponin I is detected at sub-picomole per litre concentrations in a few minutes. The optomagnetic technology is fundamentally suited for high-performance integrated testing and is expected to open a new paradigm in biosensing.

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.

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.

Signal processing for 35GB on a single-layer Blu-ray disc

We report on the technical progress in increasing the recording density of optical storage systems by means of improved read-channel signal processing and write-channel optimisation. The recording density increase is realized by employing PRML (Viterbi) bit detection in combination with improved timing recovery and adaptive equalisation algorithms, and by using a signal quality characterisation scheme which enables a proper control of the write process in the considered range of storage densities. The Blu-ray Disc (BD) optical disc system employing blue-violet laser with the wavelength of 405nm, objective lens with numerical aperture of 0.85 and disc cover layer thickness of 0.1mm is used as an experimental platform in our present study. Multi-track experimental results for both single-layer read-only (BD-ROM) and single-layer rewritable (BD-RE) media are presented to show the feasibility of the increased-density BD.

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.