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

In optical data storage systems, the areal density can be increased using a near-field optical technique such as that using a solid immersion lens (SIL) as reported by Kino et al.(1). To achieve reasonable efficiency of writing/reading signals using evanescent coupling, it is important that the spacing between the lens surface and the recording layer be reduced to around one-tenth of the wavelength, to around 50nm. Although a combination of an SIL and a flying head in a hard disk drive has been proposed initially by Terris et al.(2), the integration of a flying head and an SIL with the accuracy required by a near-field optical lens system is clearly a major consideration. Negative-pressure-cavity (NPC) sliders are now used in hard-disk drives to achieve ultra-low flying height. The NPC structure is fabricated using photolithography and ion-milling. In a near-field optical system using a magneto-optical (MO) medium, the recording head is positioned on the slider. Thin-film magnetic coils fabricated on the slider surface using photolithography is a practical solution to integrating recording coils with a flying-head structure. At present, lenses are individually fabricated and positioned on the slider but we propose that multiple hemispherical lenses be embedded in a substrate, then fabricated to an optical flying head using photolithography.