Heat-assisted magnetic recording is a promising approach for enabling large increases in the storage density of hard disk drives. A laser is used to momentarily heat the recording area of the medium to reduce its coercivity below that of the applied magnetic field from the recording head. In such a system, the recording materials have a very high magnetic anisotropy, which is essential for the thermal stability of the magnetization of the extremely small grains in the medium. This technology involves new recording physics, new approaches to near field optics, a recording head that integrates optics and magnetics, new recording materials, lubricants that can withstand extremely high temperatures, and new approaches to the recording channel design. This paper surveys the challenges for this technology and the progress that has been made in addressing them.

Heat Assisted Magnetic Recording

A nitride semiconductor device including a light emitting device comprises a n-type region of one or more nitride semiconductor layers having n-type conductivity, a p-type region of one or more nitride semiconductor layers having p-type conductivity and an active layer between the n-type region and the p-type region. In such devices, there is provided with a super lattice layer comprising first layers and second layers which are nitride semiconductors having a different composition respectively. The super lattice structure makes working current and voltage of the device lowered, resulting in realization of more efficient devices.

Nitride semiconductor device

A recording density of 1.5 Pb m−2 using heat-assisted magnetic recording in a bit-patterned media is demonstrated. This represents a dramatic improvement in track width and optical efficiency over continuous media, owing largely to advantageous near-field optical effects.

Magnetic recording at 1.5 Pb m −2 using an integrated plasmonic antenna

A nitride semiconductor element exhibiting low leakage current and high ESD tolerance includes an active layer of nitride semiconductor that is interposed between a p-sided layer and an n-sided layer, which respectively consist of a plurality of nitride semiconductor layers, the p-side layer including a p-type contact layer as a layer for forming p-ohmic electrodes, the p-type contact layer being formed by laminating p-type nitride semiconductor layers and n-type nitride semiconductor layers in an alternate manner.

Nitride semiconductor element

An apparatus and method for distracting, in a given direction, and supporting two tissue surfaces. A plurality of wafers are consecutively inserted between the two tissue surfaces to create a column of wafers. The column of wafers is oriented between the tissue surfaces so as to expand in the given direction as the wafers are consecutively added to the column.

Tissue distraction device

An information processor of a high reliability and a high recording density, and a blue color, blue-violet color and violet color based semiconductor light emitting device operable at a low threshold current density, used for the same, are provided. An optical information processor of a high reliability and a high recording density enables a moving picture, such as a high-definition television picture, to be recorded and reproduced satisfactorily. A barrier layer in a quantum-well active layer of a semiconductor light emitting device is doped with n-type impurities at a high density. Alternatively, the face orientation of a quantum-well active layer of a semiconductor light emitting device is a plane inclined from the (0001) plane, whereby the threshold current value of the semiconductor light emitting device can be decreased. The semiconductor light emitting device is typified by a gallium nitride based compound semiconductor laser device.

Optical information processing equipment and semiconductor light emitting device suitable therefor

A near-field probe includes a metallic scatterer fabricated on a substrate in a contour of a circular cone, a polygonal pyramid, a planar ellipse, or a triangle and a film of a metal, a dielectric, or a semiconductor formed in a periphery of the scatterer with film thickness equal to height of the scatterer.

Near-field optical probe, near-field optical microscope and optical recording/reproducing device with near-field optical probe

The optical head is arranged such that a semiconductor laser and a photodetector are formed via a buffer layer on the same substrate; and an opening portion is formed in the substrate under the semiconductor laser and the photodetector This optical head is further arranged by that the opening portion is filled with a first transparent layer; a diffraction grating is formed on a lower surface of the first transparent layer; a second transparent layer is stacked on a lower surface of the first transparent layer; and a condenser lens is formed on a lower surface of the transparent layer In this optical head, laser light emitted from the semiconductor laser is penetrated through the substrate, the first transparent layer, the diffraction grating, and the second transparent layer, and condensed toward a place just under the condenser lens by the condenser lens, thereby forming a light spot on an optical storage medium positioned apart from the condenser lens, whereas reflection light reflected from the optical storage medium is penetrated through the condenser lens and the second transparent layer, diffracted by the diffraction grating toward a light receiving plane of the photodetector, and further penetrated through the first transparent layer to be received by the photodetector

Flying type optical head integrally formed with light source and photodetector and optical disk apparatus with the same

An interference type optical head and an optical disk device that can easily adjust an optical path length difference of a couple of lights, ensure higher signal amplification effect, and are suitable for reduction in size are provided in order to improve a regeneration signal quality with amplification of signal in the case where reflectivity of each layer must be lowered and relative noise for the signal increases because read speed is high in a multilayer optical disk. In view of essentially improving an S/N ratio of the regeneration signal in high-speed rotation of a multilayer disk, a plurality of interference phases are generated and an optical system for differential calculation has been reduced in size with an angular selective polarization conversion element in the optical disk device for amplifying the signal with interference of the light not radiated to the disk with the reflected light from the disk. Moreover, adjustment of reflection mirror angle of the reference light is no longer required by using a corner cube prism as the reference light reflection mirror and highly accurate signal detection can also be realized with a simplified structure.

Optical head and optical disk device

The distribution of the optical near-field generated by a probe with a wedge-shaped metallic plate was calculated using a finite difference time domain method. The dependence of the distribution on the size and the material of the metallic plate was calculated, and it was shown that a strong optical near-field was generated at the apex of the metallic plate when the size and the material were optimized so that a surface plasmon was excited in the metallic plate. The influence of the recording medium was also calculated. The resonance wavelength shifted toward a longer wavelength and the decay length of the optical near-field increased when the recording medium was placed near the probe. The spot size calculated on the surface of the recording medium was 30 nm, and the efficiency (defined as the ratio between the power of the optical near-field at the surface of the recording medium and that of the incident light) was about 20% when the spacing between the probe and the recording medium was 10 nm. The near-field distribution for a probe with two metallic plates was also calculated, and it was shown that a strong optical near-field was generated between the apices of the metallic plates when the plasmon was excited in the metallic plates.

Takeshi Shimano

Papers

Optical information processing equipment and semiconductor light emitting device suitable therefor

Near-field optical probe, near-field optical microscope and optical recording/reproducing device with near-field optical probe

Flying type optical head integrally formed with light source and photodetector and optical disk apparatus with the same

Optical head and optical disk device

Highly efficient probe with a wedge-shaped metallic plate for high density near-field optical recording