Naoto Kojima

Flying characteristics of a novel negative pressure slider “Papillon”

This paper proposes a novel design of a 50% shaped rail negative pressure air bearing slider, the Papillon slider. This design attains constant fly height and near-zero roll characteristics across the disk, simultaneously. The head roll due to seek acceleration is suppressed by controlling static roll angle and improving roll stiffness of the air bearing. It is shown that the side rail shape can be configured so as to improve the roll stiffness. Experiments also show that the Papillon slider has good takeoff and contact start/stop performance.

A Write Head Integrated With a Solid-Immersion-Lens System for Heat-Assisted Magnetic Recording

We have developed for heat-assisted magnetic recording a novel write head in which a magnetic writer and a near-field optical lens system are integrated. The single-pole type (SPT) write head is embedded in the hemispherical lens of a solid immersion lens (SIL) system, which has an effective NA of 1.44 at a wavelength of 405 nm. The SPT head, which has high magnetic efficiency and minimizes light scattering, consists of a main pole and vertical-turns type (VTT) coils. With an FWHM spot diameter of 130 nm and a main pole 2 mum wide, the head is estimated to be capable of small-spot writing

An Optical Configuration Based on Flying Head Structure for Near-Field Recording

We report an optical configuration with a flying head for a near-field recording system. The configuration consists of a fixed optical unit and condensing optics based on the flying head structure. While the fixed optical unit includes a light source and a signal-detection unit, the condensing optics include a solid immersion lens (SIL) embedded in the flying slider and infinite objective lens arranged on the flying slider. Free-space propagation using a collimated beam is employed to optically connect these two units. After we investigated the head structure and its fabrication process, we evaluated the fabricated optical flying head, both as an optical head and a flying head. The jitter was 8.87% when the shortest mark length was 0.364 µm. The C/N ratio was 49.53 dB for 0.2 µm of the mark length. The tolerances of relative tilt and decenter between the two optical axes of the fixed optical unit and the condensing optics which were derived experimentally were ±0.3 deg and ±150 µm. These results suggest that the optical configuration is adequately practical even for use in mass production.

Optical flying head for a near-field recording system

We report a novel optical head based on the combination of a solid immersion lens and fiber optics with a flying slider for a practical near-field recording system. The configurations proposed here, are capable of near-field recording using magneto-optical detection and phase-change detection. 50nm of the flying height of the optical slider was obtained at a linear velocity of 10m/s. The effective numerical aperture of the SIL itself was 1.24 and the rms value of the wavefront aberration of the SIL was 0.0367 lambda. This rms value can realize an accurate readout at a practical level. Further, the carrier to noise ratio for the mark length of 0.2 micrometers on a spin stand was about 41 dB. This result indicates that a SIL can be combined with a flying slider for near-field recording.

Shape effects of GeSbTe nanodots on the near-field interaction with a silver triangle antenna

We investigated the shape effects of GeSbTe nanodots on the near-field interaction with a silver triangle antenna using the three-dimensional finite-difference time-domain method, avoiding the difficulty of detecting near-field signals from a single dot that occurs in current measurements. The surface plasmon resonance of silver strengthens the near-field around nanodots made of GeSbTe, commonly used in phase-change recording. Using GeSbTe spheres and pillar dots with various top plane shapes, we investigated the relationship between the inner electric field concentration of GeSbTe nanodots and the radius of curvature of the corners facing the antenna tip. Reducing the radius of curvature strengthens the inner electric field of the dots, enhancing the near-field difference in intensity for the GeSbTe phase change. GeSbTe diamond pillars with a radius of curvature of 1 nm exhibit a near-field difference in intensity of 28% for the phase change. Using the antenna and the GeSbTe nanodot array, optical write-once recording is realized. The preliminary research in this study is expected to realize future optical disk storage using GeSbTe nanodots with diameters below 10 nm.

High Resolution Readout Using a Near-Field Optical Probe Embedded in a Condensed Lens

We have developed a novel head structure with an embedded near-field optical probe in a solid immersion lens system. This head structure is suitable for optical probe detection using Scanning Interferometric Apertureless Microscope (SIAM) technology. We fabricated a hemispherical lens with an embedded near-field optical probe. The dielectric coupling between probe and medium generates a signal beam with a scattered field which results in a small phase shift. We can observe the surface features of the medium by detecting the degree of phase. In this way, periodic signals from lands shorter than the optical cutoff can be detected. The signal intensity decreases to 1/e2 with a spacing of 60 nm. The detected signals are generated by the near-field optical probe.

An optical flying head for a near-field recording system: part II

At the last ODS 2001, we reported a SIL-embedded optical flying head combined with fiber optics for a near-field recording (NFR) system (Tech. Dig. Optical Data Storage, April 2001). We report further study of an optical flying head without fiber optics for a near-field recording system. After describing the configuration of the optical flying head, the readout signals and tolerances are presented. The C/N (carrier to noise) ratio was 49.53 dB for 0.2 gm of the mark length. The tolerances of relative tilt and decenter were /spl plusmn/1deg and /spl plusmn/100 gm, respectively. We think a more practical head structure can be realized by miniaturizing the condensing optics on the flying head.

Practical fabrication of an optical flying head for a near-field recording system

We have developed a new optical flying head integrating a solid immersion lens and a flying slider for application to an ultra high-density storage system. We report a practical method of fabricating this head. The flying head has a stable flying attitude at the flying height of 50nm.