Kiichi Ueyanagi

Grinding Characteristics of Solid Immersion Mirrors with the ELID Grinding Method

This study describes the grinding of solid immersion mirrors wi th paraboroidal surfaces using a four-axis ultrahigh precision machine tool with an ELID s ystem and a contact probe for on-machine measurement. Results of the grinding experiments indica ted that good form accuracy was achieved successfully. Introduction The near field optical recording technologies using a solid immersi on lens (SIL as shown in Fig. 1 [1]) or solid immersion mirror (SIM as shown in Fig. 2 [2]) have b en proposed as promising candidates to overcome the density limit of conventional optical recordings with far field optics. Scanning type Beam Laser / Detector SIL Collimator Lens Mirror Objective Lens SIM Scanning type Beam Laser / Detector Collimator Lens Fig. 1 Solid Immersion Lens (SIL) Fig. 2 Solid Immersion Mirror ( SIM) The recording density of 50Gbpsi has been already attained with a SIL, which is the highest one in a single layered recording [3]. These devices are also suitable for the OAM (opticallyassisted magnetic) recording technologies with avoiding the super paramagnetic problem in HDD [4]. However, non-removable type system is preferred to the near field recording with a SIL or SIM because the air gap between their surface and recording layers should be reduced to le ss than 100nm so as to the evanescent wave penetrate into the recording layers . In such kind of usage, the HDD is a main competitor and so the head size and weight, especially it s height, should be reduced to those of the magnetic heads to make the volume density and transfer rat e become competitive. According to this standpoint, Fuji Xerox Co., Ltd proposed three years ago an optical head with a new type of a solid immersion mirror which consists of a hemi-paraboroidal, refl ecting surface, and incident and Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 83-88 doi:10.4028/www.scientific.net/KEM.238-239.83

Fabrication and optical characteristics of a hemi-paraboloidal solid immersion mirror and designing of an optical head with the mirror

A hemi-paraboloidal solid immersion mirror is successfully fabricated with the ELID (electrolytic in-process dressing) grinding technology and the spot size obtained was 150% of that for diffraction limited processes. Small sized optical head would be possible with the HP-SIM, which size is comparable to that of a magnetic head for HDDs.

New flying optical head for high-speed accessing

A flying optical head has been developed to attain high speed accessing, the important issue in applying optical disks for computer file memories, because the head weight could be ultimately reduced. And it was successfully applied for writing and reading of optical disks for the first time. The moving part of the head consists of an objective lens, mirror, flying slider and moving coil of a voice coil motor and a linear bearing, which total weight is as light as 3.6gr. The flying slider makes the objective lens follow on a disk surface, so the variation of the distance between the lens and the optical disk caused by the axial runout of the disk is largely reduced. Autofocusing is done by axial moving of relay lenses which are placed in the fixed part of the head. The resonant frequency of the moving part has been improved to more than 10kHz by reducing its weight, which enables it to do track-following as well as track-seeking. Seek time of less than 20 ms for a 130mm disk was achieved with the flying optical head.

Write-once recording by phase separation

Highly stable and fast response write once recording was achieved by a new phase separation recording method involving binodal decomposition of nonstoichiometric Tellurium oxide polycrystal deposited by RF ion plating. Response to writing was saturated completely after one disk rotation ( 33 msec ). Degradation of film exposured to high temperature and high humidity was little. So, if the Arrhenius method was adopted, the life was estimated at infinite.