KEYWORDS: Head, Near field, Near field optics, Phase modulation, Polarization, Near field scanning optical microscopy, Aluminum, Signal detection, Interferometers, Mirrors
Near-field optics is one of super-resolution techniques for future data storage system. We have already proposed a near-field optical flying head with a circular aperture. Realizing higher performance aperture, we also have developed a triangular one which has been experimentally evaluated with scanning near-field optical microscope probe. In this paper, we demonstrate readout performance of this novel aperture mounted near-field head introducing polarization control. In order to scan over a media surface at small spacing condition, we fabricate a "contact" type head having contact pads and a polarization maintaining fiber, because this type of an aperture can only effectively function on condition both of extremely small spacing and applying polarized light. The contact pads and the tip are formed by photolithography with hydrofluoric acid (HF) solution. An aluminum film is formed on the tip. The aperture is formed by squeezing the shading film. Measurement of surface configuration by an interferometer shows that the aperture and the contact pads are almost on the same plane within 5 nm deviation. The media consists of a glass substrate, a titanium layer, a carbon protective layer, and a lubricant layer in sequence. Line-and-space (L&S) patterns whose width are 40~200nm are formed on the titanium layer. The contact head approaches the media surface, and then the media is scanned by a piezo stage. The near-field light generate from the triangular aperture is scattered by the L&S pattern and detected by a photomultiplier tube. Signal readout from the 40-nm-wide L&S pattern is demonstrated.
Recent rapid progress in a digital network society necessitates storage devices with higher-density and faster transfer rates. In optical storage, a novel recording principle is eagerly awaited that will drastically improve recording density without being restricted by a wavelength shortening limit or a numerical aperture (N.A.) limit of the optics utilized. Storage based on the "near-field" principle is thought to be one of the most promising breakthroughs for overcoming various tough limitations governing traditional optical recording. From this perspective, we have already proposed an
integrated optical head slider assembly that relies on the novel near-field principle for its operation; it is mounted on a minute tapered aperture and has a planar focusing lens and a micro silicon mirror. Readout signals corresponding to a 200-nm-long bit have demonstrated a frequency band up to approximately 10 MHz, using a chromium patterned medium. In this study, we have investigated a tribological (glide height) property and flying stability of a miniaturized
1.5-mm-long optical head slider by using acoustic emission sensor signal and readout signal from the medium. We have also evaluated detecting performance separately using traditional 3.2-mm-long slider and a chromium patterned medium whose bit patterns are accurately scored with bit lengths less than 100 nm using electron beam lithography including reactive ion etching. We have confirmed stable flying performance of 1.5-mm-long slider assembly and furthermore,
ability of detecting sub-100-nm long bit patterns.
KEYWORDS: Head, Near field optics, Waveguides, Photoemission spectroscopy, Signal detection, Optical tracking, Optical recording, Metals, Near field, Near field scanning optical microscopy
Optical near-field recording is a candidate technology for overcoming the diffraction limit of conventional optical recording. In our previous work, we proposed a novel optical head slider for near-field recording that we call a flexible optical head slider. An air-bearing pad pattern is formed on the apex of a cantilever-like polymeric waveguide so that, by using the cantilever itself as the slider suspension, a single body structure incorporates the functions of the flying slider, suspension, and waveguide. This structure can be expected to provide several important advantages by miniaturizing head assemblies; simplifying the assembly and optical trimming processes; and producing a lighter head, thus allowing a wider tracking bandwidth. In our previous report, the mechanical characteristics and readout signal characteristics of the flexible head slider were evaluated.
In this paper, we studied the tracking control for the flexible optical head slider. To detect tracking errors, a T-shaped aperture was used. One straight part of the T-shaped aperture was set along the edge of the tracks, so the transmitted light from this part is sensitively affected by off-track displacement. Another straight part is used for readout of the data marks. The T-shaped aperture was formed through the metal layer deposited on the slider pad surface, at the end of the waveguide core, using FIB (focused ion beam) etching. Test ROM media with repeated pattern of 0.5 micron-sized dot marks was used to evaluate the position error signal.
Advances in a digital network society require both higher densities and higher transfer rates in all sorts of storage devices. In optical recording, the trend toward higher recording density and larger storage capacity requires novel surface recording technologies that would drastically improve recording density. To satisfy these severe requirements, we have already proposed a compact integrated optical head slider assembly for proximity optical recording based on the "near field principle". Using the optical head slider, we have successfully demonstrated readout signals from 200 to 150-nm-long bit patterns at frequency bands up to approximately 10 MHz. However, from the practical point of view, it is quite necessary to evaluate readout signals from patterns of smaller (sub-micron to sub-sub-micron) track width in order to prove high-density recording potential. In this paper, we have investigated tracking accuracy characteristics utilizing sub-micron sized alternate patterns of 1-mm length formed in a straight line in the circumferential direction of the medium. Arranging precisely the head's relative position to these recorded patterns, we have successfully obtained readout signals just crossing the sub-micron line-and-space pattern's boundaries. Assuming that an aperture runs along an accurate trajectory of the arc of a circle, readout signal amplitude variations when crossing the pattern edge at a right angle have precisely predicted. Also, the influences of track width on maximum readout signal intensity and tracking sensitivity are discussed in detail.
KEYWORDS: Near field scanning optical microscopy, Light scattering, Near field optics, Micromachining, Near field, Sensors, Atomic force microscopy, Photodiodes, Signal detection, Spatial resolution
We have developed an integrated micro-probe with improved detection efficiency for apertureless near-field scanning optical microscopy (NSOM) by using micromachining techniques; we call this probe a `photocantilever'. A photocantilever is an integrated micro-cantilever with a pn- junction at its end; it is fabricated using micromachining techniques. It has achieve higher collection efficiency than conventional NSOM probes because the detector is placed close to the scatterer. Two new types of NSOM can be performed using this photocantilever: totally-internal- reflection-illumination-based NSOM and differential NSOM. Both provide NSOMs with high spatial resolution. The photocantilever enables apertureless NSOM with high collection efficiency and high resolution.
Conference Committee Involvement (3)
Optomechatronic Micro/Nano Devices and Components II
4 October 2006 | Boston, Massachusetts, United States
Optomechatronic Micro/Nano Devices and Components
5 December 2005 | Sapporo, Japan
Optomechatronic Micro/Nano Components, Devices, and Systems
27 October 2004 | Philadelphia, Pennsylvania, United States
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