Abstract:
An optical read/write head system having a support structure, an optical coupling element and a magnetic data coupling element is disclosed. The optical coupling element is provide on the support structure and is configured to couple optical signal to and from a recording medium. The magnetic data coupling element is also provided on the support structure and is configured to couple magnetic signal to and from the recording medium. The two elements operate in combination to provide more effective reading and writing than with either element alone.

Description:
CROSS-REFERNCE TO RELATED APPLICATION 
     This application claims the benefit of the priority of U.S. Provisional Application No. 60/151,617, filed on Aug. 31, 1999, and entitled Hybrid Optical Head for Data Storage. 
    
    
     BACKGROUND 
     The present disclosure generally relates to data storage systems such as disk drives and more specifically, to a read/write head for use in optical and magneto-optical data storage systems to enable hybrid transduction of data from, and to a storage medium. 
     A conventional data storage system may include a magnetic head that has a slider element and a magnetic read/write element. The system may also be coupled to a rotary actuator magnet and a voice coil assembly by a suspension and an actuator arm positioned over a surface of a spinning disk. In operation, a lift force may be generated by the aerodynamic interaction between the magnetic head and the spinning disk. The lift force is opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the spinning disk. 
     Flying head designs have been proposed for use with optical and magneto-optical (MO) storage technology. One motivation for using the magneto-optical technology stems from the availability of higher areal density with magneto-optical storage disks than magnetic storage disks. However, despite the historically higher areal storage density available for magneto-optical disk drives, the prior art magneto-optical disk drive volumetric storage capacity has generally not kept pace with the volumetric storage capacity of magnetic disk drives. 
     SUMMARY 
     In recognition of the above-described difficulties, the inventors recognized the need for high-resolution, high-density reading and writing on data storage media. 
     The present disclosure describes an optical read/write head system having a support structure, an optical coupling element and a magnetic data coupling element. The optical coupling element is provide on the support structure and is configured to couple optical signal to and from a recording medium. The magnetic data coupling element is also provided on the support structure and is configured to couple magnetic signal to and from the recording medium. The two elements operate in combination to provide more effective reading and writing than with either element alone. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Different aspects of the disclosure will be described in reference to the accompanying drawings wherein: 
     FIGS. 1A and 1B illustrate a hybrid-type head design in accordance with an embodiment of the present system; and 
     FIG. 2 illustrates an embodiment of the hybrid head design in a far-field environment; 
     FIG. 3 shows an embodiment  300  of the present system with an MSR medium used as a magnetic strip; 
     FIG. 4 shows an embodiment of the present system with a MAMMOS medium used as a magnetic strip; 
     FIG. 5 shows an embodiment of the present system with giant magneto-resistive (GMR) material used as a magnetic strip; 
     FIG. 6 shows another embodiment of the present system with GARNET transparent material used as a magnetic strip; and 
     FIG. 7 is a block diagram of an optical storage system having a hybrid read/write head of the present system. 
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes a hybrid-type head design  100  arranged to provide high-resolution, high-density reading and writing. The hybrid head  100  utilizes both optical and magnetic couplers to couple optical and magnetic signals to a recording medium. 
     FIGS. 1A and 1B illustrate an embodiment of the hybrid head design  100  viewed from the bottom and the side, respectively. The hybrid head  100  includes an objective lens  112 , a solid-immersion lens (SIL)  102  and a closely spaced magneto-resistive (MR) head  104 . 
     SIL lens  102  and inductive coil  106  may provide near-field recording on a recording material. The coil  106  produces a magnetic field having a component perpendicular to the recording media at the location where the light beam is focused. The magnetic field produced by the coil  106  may also be precisely focused at the location where the light beam is focused. 
     The constituent optics may include a reflector  116 , an objective lens  112 , and a solid immersion lens  102 . Each of these may be mounted to the slider  118 . The SIL may be substantially or entirely contained within the slider  310 . The objective lens  112  is mounted onto or near the top surface of the slider  118  to focus the incident electromagnetic radiation  114 , such as a laser beam, onto the SIL  102 . An optical clear path  120  is provided between the SIL  102  and the objective lens  112  so that the electromagnetic radiation may be effectively transmitted from one to the other and back again. The optical clear path  120  may include any optically transparent material, and may be air, glass, optically clear plastic, and so on. 
     The electromagnetic radiation  114  traveling through the optical clear path  120  may be incident on the partial spherical surface  122  of the SIL. The SIL  102  may be a single partial sphere or a lesser portion of a partial sphere plus a flat plate. The SIL  102  generally has a spherical portion  122  and a flat portion  124 , which may be a flat surface or a flat plate. The flat portion  124  may be generally co-planar with the air-bearing surface  110 . The flat portion  124  may also be in the vicinity of the air-bearing surface  110  and preferably parallel thereto. For a hemispherical SIL, the vicinity may be about the range of the dimensional tolerance of the hemispherical SIL, which may be about tens of microns. for a typical hemispherical SIL. For a super-hemispherical SIL, the vicinity may be about less than 1 micron. Such geometry may assist the flight of the head  100  over the recording medium, and forms part of the total slider-air bearing surface. 
     The optical beam  114  at the exit of the flying head is tightly focused, and may be for example in the sub-micron range. Therefore, the bottom flat surface of a near-field lens  102  may be etched, ion-milled or cut away to form a mesa-like structure  108 , or tapered bottom may be used to allow small coil  106  to be formed about the focused beam. 
     The focused beam is thus converged near the mesa structure  108 . In near-field recording, the recording medium is located less than a wavelength away from the flat portion  124  of the SIL lens  102  and the mesa structure  108 . In this way, the evanescent waves of the incident wave may couple the optical energy at the small focused spot. Thus, the flying head  104  is “suspended” over the optical medium at a constant distance through air-bearing surfaces  110 . 
     Alternatively, the recording medium may be in a far-field position relative to the SIL  102 . In such a case, the medium would be located more than a wavelength away from the flat portion  124  of the SIL lens  102  and the mesa structure  108 . In a far-field configuration, the head  100  would have to be positioned above the recording medium by a servo since no air-bearing surface is created in this situation. 
     The MR head  104  may provide magneto-resistive reading of the written bits while the magnetic super-resolution (MSR) or magneto-optic (MO) media is optically heated to open the magnetic domain for readout. The MR head  104  may allow reading of narrow tracks and very high linear bit density compared to MO head. 
     In an alternative embodiment, the hybrid head design may use a wide read element that covers several tracks. The MR head  104  may then detect only the data that has been coupled to the surface by the heating of the laser. 
     The hybrid head is located generally adjacent to a recording medium. The head may be reading data from or writing data to the recording medium. In general, the recording medium can be in any format including disk or tape. Traditional magneto-optical recording uses a transparent substrate, such as glass or polycarbonate plastic, to bring any dust or other contaminant particles on the light entrance surface severely out of focus. In one implementation, the recording medium is layered on a substrate with a reflective aluminum material provided on top of the substrate. Layers for dielectric, recording, intermediate coupling, and readout functions may then be provided in sequence. A transparent overcoat layer may be deposited on top to protect the medium. 
     An embodiment of the hybrid head  200  design in a far-field environment is illustrated in FIG.  2 . The head design may include an MR head  202  and an objective lens  204 . The design may also include an actuator/servo  206  to maintain a constant distance between the head  200  and the recording medium. The actuator  206  may be incorporated into a suspension or a slider  208 . 
     In some embodiments, flying MO head having SIL lens may be used to pick-up MO written domains. For these embodiments, the domain size may often be limited by the resolution of the beam spot focused by the SIL lens in the MO head. Further, the signal-to-noise ration (SNR) may drop significantly as the domain size is reduced. 
     FIGS. 3 through 6 illustrate different hybrid head designs to improve the. resolution of the SIL system. The designs involve coating the bottom of the SIL lens with a magnetic masking and detection strip. The magnetic properties of the strip are modified as a function of exchange field from the written domains by thermally activating a small area on the SIL lens with a laser. Further, alignment between the magnetic sensor and the data may be maintained by using the same laser spot transmitted through the SIL lens for tracking. 
     The magnetic strip may be a single or a combination of magnetic layers with ferri- or ferro-magnetic properties. In-plane or perpendicular magnetic anisotropy may depend on the detection technique used such as magnetic super-resolution (MSR), magnetic amplifying magneto-optical system (MAMMOS), or magneto-resistance (MR). The magnetic properties of the magnetic strip such as coercivity, magnetization, and anisotropy are expected to vary as a function of temperature and exchange coupling from the written domains on the media. The thermal assistance may be provided by the laser spot, which produces a ‘window’ in the masking properties of the magnetic strip. This inhibits is inadvertent sensing of adjacent domains referred to as inter-symbol interference. 
     The read back signal may be detected by means of the Kerr effect or the magneto-resistive effect. In detecting the Kerr effect, the laser light is used to detect up or down magnetic states. For the magneto-resistive effect, an electric connection is made to the boundaries of the magnetic layer to sense the change in resistance as a function of magnetic state. A coil structure may be used around the bottom of the SIL lens in order to initialize the layer in a given direction. The structure may also be used to expand and collapse domains on the MAMMOS. 
     FIG. 3 shows an embodiment  300  of the present system with the MSR used as a magnetic strip  302 . The strip  302  may be formed of a GdFeCo layer or other suitable layer. The laser spot  304  transmitted through the SIL lens  306  thermally activates a small area  308  on the magnetic strip  302  to change the magnetization of the small area  308  in accordance with the orientation of the written domain  310  under the illuminated area. Thus, the magnetic strip  302  acts as a readout layer with the laser spot  304  providing a window in the masking properties of the magnetic strip  302  to reduce any interference. 
     An embodiment  400  of the present system with the MAMMOS used as a magnetic strip  402  is shown in FIG.  4 . In the illustrated embodiment, the MAMMOS  402  is configured to amplify a signal of a domain  404  in the recording layer  406 . For example, an amplifying layer of TbFeCo may be used to ensure enhanced playback of high-density recording spots, e.g., with a spot size less than 0.1 μm in diameter. 
     In a readout operation, a small area  408  on the MAMMOS  402  may be heated by a laser beam  410 . Magnetic transformation may cause a new domain with the same magnetic orientation to form on the magnetic strip  402  of MAMMOS. The newly formed magnetic domain on the strip  402  expands if an external magnetic field is applied,in the same direction as the local magnetic orientation. This amplification improves the signal detection in readout or enhances the apparent signal-to-noise ratio of the recorded bit. A reversed external magnetic field may be applied to an amplified domain to eliminate or collapse the domain in the amplifying layer after the domain is read out and before the next domain is amplified for readout. Hence, the external magnetic field may be modulated at the data rate of the storage system. 
     FIG. 5 shows an embodiment  500  of the present system with giant magneto-resistive (GMR) material used as a magnetic strip  502 . Again, the laser spot  504  transmitted through the SIL lens  506  thermally activates a small area  508  on the magnetic strip  502 . An electrical connection  510  is made to the boundaries  512  of the magnetic strip  502  to sense the change in resistance as a function of magnetic state of the written domain  514  on the recording medium  516 . 
     FIG. 6 shows another embodiment  600  of the present system with GARNET transparent material used as a magnetic strip  602 . GARNET material generates high Kerr signal, which provides high signal-to-noise ratio data. 
     FIG. 7 is a block diagram of an optical storage system  700 , which includes a hybrid read/write head  714 . The system  700  provides a user interface  704  of data input  706  through main electronic control  702  which is preferably implemented to monitor and control all components and subsystems. The user interface  704  includes, but is not limited to, a computer keyboard, a display, electrical and mechanical switches and control buttons. The system  700  also includes a data storage medium  708  in the form of a disk or other format. In some embodiments, the disk is a magneto-optic disk, a write-once disk, a phase-change disk, or a read-only disk. 
     In one embodiment, a flying read/write head  714  and the data storage medium  708  are positioned relative to each other so that the optical spacing therebetween is less than one wavelength of the light produced by the light source  710  in a near-field configuration. An air-bearing surface is preferably implemented at the base of the flying head  714  to maintain a desired focus without conventional servo optics for focusing. Alternatively, a far-field configuration can also be used with the flying head  714 , in which case the separation between the flying head and the recording layer does not allow efficient coupling of evanescent waves and thus a conventional servo focusing system is needed to directly focus the beam onto the recording surface. 
     In a readout operation, a reflected laser beam may be modulated with both tracking information and the data stored on the storage medium  708 . In a recording operation, the reflected laser beam from the optical medium  708  may be encoded with beam-tracking information. Recording data onto the storage medium  708  may be done by either modulating a writing beam via an optical modulation including beam intensity, phase, and polarization either at the light source  710  or at the beam relay system  712 , or directly modulating the state of the data storage medium  708  through thermal or magneto-resistive methods. 
     While specific embodiments of the invention have been illustrated and described, other embodiments and variations are possible. 
     All these are intended to be encompassed by the following claims.