Abstract:
A transducer assembly for a data storage system comprises a first transducer for directing electromagnetic radiation onto a storage medium adjacent to a write pole, and a second transducer for directing electromagnetic radiation onto a storage medium adjacent to a read sensor. A data storage apparatus that includes the transducer assembly is also included.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0001]     This invention was made with United States Government support under Agreement No. 70NANB1H3056 awarded by the National Institute of Standards and Technology (NIST). The United States Government has certain rights in the invention. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to transducers for concentrating electromagnetic radiation, and more particularly, to such transducers for use in data storage applications.  
       BACKGROUND OF THE INVENTION  
       [0003]     Heat assisted magnetic recording (HAMR) generally refers to the concept of locally heating a recording medium to reduce the coercivity of the recording medium so that the applied magnetic writing field can more easily direct the magnetization of the recording medium during the temporary magnetic softening of the recording medium caused by the heat source. Heat assisted magnetic recording allows for the use of small grain media, which is desirable for recording at increased areal densities, with a larger magnetic anisotropy at room temperature to assure sufficient thermal stability. By heating the medium, the material&#39;s magnetic crystalline anisotropy energy density or the coercivity is reduced such that the magnetic write field is sufficient to write to the medium. Once the medium cools to ambient temperature, the medium has a sufficiently high value of coercivity to assure thermal stability of the recorded information.  
         [0004]     It is well-known in magneto-optical (MO) recording that there are media that require heating in order for the information to be retrieved from a disc. For example, MO recording media comprised of TbFeCO is extremely thermally stable due to the divergence of the coercivity of the media at room temperature. However, at room temperature the magnetization is zero making it impossible for read back using a magnetoresistive sensor. In order to read this type of medium with a magnetoresistive (MR) sensor, the medium first needs to be heated to induce a magnetization in the film. Other media that can use thermally assisted read back include magnetic super resolution media, MAMMOS (Magnetic Amplifying MO System) media, and various exchange spring type media.  
         [0005]     Transducers have been proposed for use in heat assisted magnetic recording (HAMR) wherein the light delivery system is aligned only with the writer and not the reader. Furthermore, given the complexity of the alignment problem, it does not seem likely that it will be possible to design a transducer where the reader and writer can be simultaneously aligned with the light delivery element.  
         [0006]     There is a need for a transducer assembly that can be used in storage devices using thermally assisted writing and read back.  
       SUMMARY OF THE INVENTION  
       [0007]     This invention provides a transducer assembly for a data storage system comprising a first transducer for directing electromagnetic radiation onto a storage medium adjacent to a write pole, and a second transducer for directing electromagnetic radiation onto a storage medium adjacent to a read sensor.  
         [0008]     In another aspect, the invention provides a data storage apparatus comprising a storage medium; and an arm for positioning a recording head adjacent to the storage medium; wherein the recording head includes a transducer assembly comprising a first transducer for directing electromagnetic radiation onto a storage medium adjacent to a write pole, and a second transducer for directing electromagnetic radiation onto a storage medium adjacent to a read sensor. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a pictorial representation of a disc drive that can include the transducer assemblies of this invention.  
         [0010]      FIG. 2  is a schematic representation of an end view of a slider including a transducer assembly constructed in accordance with the invention.  
         [0011]      FIG. 3  is a schematic representation of a side view of another slider including a transducer assembly constructed in accordance with the invention.  
         [0012]      FIG. 4  is a schematic representation of a side view of another slider including a transducer assembly constructed in accordance with the invention.  
         [0013]      FIGS. 5, 6  and  7  are schematic representations of portions of recording head assemblies including transducer assemblies constructed in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     This invention encompasses structures that can be used in recording heads for use with magnetic and/or optical recording media, as well as magnetic and/or optical recording heads that include such devices and disc drives that include the recording heads.  FIG. 1  is a pictorial representation of a disc drive  10  that can utilize transducer assemblies constructed in accordance with this invention. The disc drive includes a housing  12  (with the upper portion removed and the lower portion visible in this view) sized and configured to contain the various components of the disc drive. The disc drive includes a spindle motor  14  for rotating at least one data storage medium  16  within the housing, in this case a magnetic disc. At least one arm  18  is contained within the housing  12 , with each arm  18  having a first end  20  with a recording and reading head or slider  22 , and a second end  24  pivotally mounted on a shaft by a bearing  26 . An actuator motor  28  is located at the arm&#39;s second end  24 , for pivoting the arm  18  to position the head  22  over a desired sector of the disc  16 . The actuator motor  28  is regulated by a controller that is not shown in this view and is well-known in the art.  
         [0015]     For heat assisted magnetic recording, an electromagnetic wave of, for example, visible, infrared, or ultraviolet light is directed onto a surface of a data storage medium to raise the temperature of a localized area of the medium to facilitate switching of the magnetization of the area. Solid immersion lenses (SILs) and solid immersion mirrors (SIMs) have been proposed for use in reducing the size of a spot on the medium that is subjected to the electromagnetic radiation. SILs and SIMs may be either three-dimensional or two-dimensional. In the latter case they correspond to mode index lenses or mirrors in planar waveguides. The SILs and SIMs form a condenser that directs an electromagnetic wave to a focal point. A metallic pin can be inserted at the focal point to guide a confined beam of light out of the condenser to the surface of the recording medium. The metallic pin is just an example of one type of near field transducer. The role of the near field transducer is to reduce the spot size within the condenser to even smaller spot sizes typically less than 100 nm. Other near field transducers are the ridge waveguide, apertures and optical antennas such as the bowtie antenna.  
         [0016]     Some magneto-optical (MO) recording media must be heated to retrieve information from the disc. To read this type of media with a magnetoresistive (MR) sensor, the media must be heated to induce a magnetization in the film.  
         [0017]     This invention provides a transducer assembly for heating the media to accommodate both writing and reading. The transducer assembly includes two transducers that can be mounted on a slider. The invention will work with all media requiring thermally assisted read back such as magnetic super resolution media, MAMMOS media and various exchange spring type media.  
         [0018]     In one example, the invention includes separate transducers for the writer and the reader. Each of the transducers includes a condenser, in the form of a waveguide, and a near field transducer. The waveguides can be, for example, SILs or SIMs and the near field transducers can be, for example, metallic pins. Each waveguide and near field transducer design can be separately optimized for writing or read back. The details of the waveguide and transducer alignment are dependent on the orientation of the medium and the chosen field delivery source and reader technology.  
         [0019]     For the writer it is desirable to maximize the power in the waveguide to heat the media and confine it to the smallest spot possible. For the reader it is desirable to have stable power to avoid introducing any nonlinearities. In addition, the reader would operate at lower power than the writer. Typically, today&#39;s hard drive write wide and read narrow. That is, the reader spot size might be smaller than the writer spot size to avoid reading information from neighboring tracks.  
         [0020]      FIG. 2  shows an example slider  30  that includes two optical transducers  32 ,  34  fabricated side by side on a back surface  36  of the slider. The optical transducers in this example include condensers in the form of solid immersion mirrors (SIMs)  38  and  40 , with gratings  42 ,  44 ,  46  and  48  for coupling electromagnetic radiation, such as infrared, visible or ultraviolet light into the SIMs. The gratings in each of the SIMs can be offset so that polarized light in one half of each SIM is phase shifted with respect to the light in the other half of the SIM. The light is directed to transducer focal points  50 ,  52  such that the electric field component of the light at the focal point is parallel to the axes  54 ,  56  of the SIMs. A metallic pin can be positioned at each focal point to concentrate the light and direct it toward the storage media. SIM  38  is positioned adjacent to a write pole  58 . Tabs  60  and  62  serve as connection points for connecting write signals to the writer. SIM  40  is positioned adjacent to a read element  64 , such as magnetoresistance element or a giant magnetoresistance element. Tabs  66  and  68  serve as connection points for connecting read signals from the read element.  
         [0021]     An optical fiber can be used to direct light onto the gratings. In this example, either the slider or the fiber can be moved so that the light is shifted from one pair of gratings to the other, depending on whether or not one is reading or writing. For example, the fiber can be fixed and the slider would be moved under the fiber. This can be accomplished using a dual stage actuator that can be modified to not only have a small actuation for tracking, but to also have a large throw for moving the slider under the fiber. Using current SIM designs the slider would have to be shifted a distance of about 100 μm. Although this distance is relatively large, it does not need to be accurate, and being off by a micron or so is not important. The advantage of this design is that both SIMs can be fabricated in the same lithography step since both SIMs are contained in a single waveguide layer in the read/write head. Instead of using a fiber, free space coupling could be used. In a free space coupling example, a laser can be mounted on the E-Block ( 24  in  FIG. 1 ) and its light can be directed to the back of the slider. The spot can be moved from one SIM to the other by either moving the slider or by moving the laser.  
         [0022]     With the example of  FIG. 2 , there is a read/write offset that can be on the order of tens of microns. This may have tracking implications as the reader will be reading a servo signal that could be  500  tracks away from the track being written.  
         [0023]      FIG. 3  is a schematic representation of another slider  80  having a transducer assembly constructed in accordance with the invention. In slider  80 , the reader  82  and writer  84  are fabricated on top of each other. A first transducer  86  is positioned adjacent to a write pole  88  to locally heat a portion of a storage medium  90  in an area subject to a magnetic field produced at the write pole. The first transducer includes a SIM waveguide  92  and can further include a near field transducer element positioned adjacent to an air bearing surface  94  of the slider. A second transducer  96  is positioned adjacent to a read element  98  to locally heat a portion of the storage medium  90  in an area near the read element. The second transducer includes a SIM waveguide  100  and can further include a near field transducer element positioned adjacent to the air bearing surface  94  of the slider.  
         [0024]     In the example of  FIG. 3 , two waveguides  92 ,  100  are again used (one for the reader and one for the writer) and separately optimized for each transducer. The waveguides are separated by a thick cladding layer  102 , which can be for example a few microns thick, to ensure that there is no cross talk between the waveguides. The waveguides can be constructed of, for example, TiO 2 , or other high index guide layer. The cladding layer can be constructed of, for example, SiO 2  or other low index cladding layer. All layers are transparent to the light.  
         [0025]     Gratings  104  and  106 , each of which can be a pair of offset gratings as shown in  FIG. 2 , are provided to couple light into the waveguides. Light, represented by arrows  108  and  110 , can be selectively launched into the waveguides by changing the coupling angle from angle “θ 1 ” for the writer to angle “θ 2 ” for the reader. Measurements have shown that a change in angle as small as only 2 degrees is sufficient to switch between the waveguides. In this example the angle could be changed by tilting the angle of an optical fiber that transmits the light from a light source, such as a laser, to the slider. Alternatively, it is also possible to change the light angle electro-optically and/or mechanically with a mirror. Devices which can be used to change the light angle do not need to be fabricated on the slider but could instead be attached to the fiber directly.  
         [0026]     If changing the angle of the incident light is not practical, it is possible to selectively couple the light into the waveguides by altering the polarization state of the incident light.  FIG. 4  is a schematic representation of another slider  120  having a transducer assembly constructed in accordance with the invention. In slider  120 , the reader  122  and writer  124  are fabricated on top of each other. A first transducer  126  is positioned adjacent to a write pole  128  to locally heat a portion of a storage medium  130  in an area subject to a magnetic field produced at the write pole. The first transducer includes a SIM waveguide  132  and can further include a near field transducer element positioned adjacent to an air bearing surface  134  of the slider. A second transducer  136  is positioned adjacent to a read element  138  to locally heat a portion of the storage medium  130  in an area near the read element. The second transducer includes a SIM waveguide  140  and can further include a near field transducer element positioned adjacent to the air bearing surface  134  of the slider.  
         [0027]     In slider  120 , the reader  122  and writer  124  are fabricated on top of each other. Here two waveguides  132 ,  140  are again used (one for the reader and one for the writer) and separately optimized for each transducer. The waveguides are separated by a thick cladding layer  142 , which can be for example a few microns thick, to ensure that there is no cross talk between the waveguides. Gratings  144  and  146  are used to couple the light into the waveguides.  
         [0028]     For this embodiment the angle θ 3  remains fixed and the polarization of the light which is coupled into the fiber is rotated by 90 degrees. In this example, the light is linearly polarized. However, the invention is not limited to use with linearly polarized light. The incident light can have two distinct polarization states that address each of the gratings separately. The grating on each of the waveguides is adjusted to couple either transverse electric (TE) or transverse magnetic (TM) modes into the waveguides. This can be accomplished by changing the grating period.  
         [0029]     Experiments have shown these gratings to be highly dependent on the polarization and almost no coupling occurs if the polarization is incorrect. This design also allows for simultaneous read back and writing, since any polarization angle can be set and the power can be shifted back and forth between the gratings. For example, if both gratings were designed to couple light equally well, a polarization angle of 45 degrees would split the light 50/50 between both gratings.  
         [0030]     There are many options for controlling the amount of light coupled into the waveguides. The light power can be adjusted at the source by changing the drive current or by modifying the grating designs. For example, the amount of light coupled into the waveguide is dependent on the grating period, grating depth, material choices, coupling angle and polarization.  
         [0031]      FIG. 5  is a schematic representation of a portion of a recording head assembly including a transducer assembly constructed in accordance with the invention. In the example of  FIG. 5 , the slider  30  of  FIG. 2  is shown to be coupled to an arm  150  by a microactuator  152 . An optical fiber  154  is used to transmit light to a mirror  156 . The light is reflected from the mirror to a grating  48  of the waveguide  40  of transducer  34 . The microactuator  152  can be used to move the slider in a direction perpendicular to the drawing sheet, so that the incident light is shifted from one waveguide to the other. Alternatively, a microactuator  158  can be coupled to the mirror to move the mirror and shift the incident light from one waveguide to the other. The arm  150  positions the slider such that the air bearing surface  160  of the slider is separated from the storage medium  162  by an air bearing  164 . The mirror (and the microactuator connected to the mirror, if used) would be supported by other structures not shown.  
         [0032]      FIG. 6  is a schematic representation of a portion of another recording head assembly  170  including a transducer assembly constructed in accordance with the invention. In the example of  FIG. 6 , the slider  30  of  FIG. 2  is shown to be supported by an arm  172 . An optical fiber  174  is used to transmit light to a grating  48  of the waveguide  40  of transducer  34 . A microactuator  176  can be used to move the optical fiber in a direction perpendicular to the drawing sheet, so that the incident light is shifted from one waveguide to the other. The arm  172  positions the slider such that the air bearing surface  178  of the slider is separated from the storage medium  180  by an air bearing  182 . The optical fiber (and the microactuator connected to the optical fiber) would be supported by other structures not shown.  
         [0033]      FIG. 7  is a schematic representation of a portion of another recording head assembly  190  including a transducer assembly constructed in accordance with the invention. In the example of  FIG. 7 , the slider  120  of  FIG. 4  is shown to be supported by an arm  192 . An optical fiber  194  is used to transmit light to the gratings  144  and  146  of the waveguides  132  and  140  of transducers. A polarization control device  196  is mounted to control the polarization of the light delivered by the optical fiber, so that the incident light coupled into one waveguide or the other, or both. The arm  192  positions the slider such that the air bearing surface  198  of the slider is separated from the storage medium  200  by an air bearing  202 . The optical fiber (and the polarization control device) would be supported by other structures not shown. Electro-optic or magneto-optic materials can be used to rotate the polarization. With these materials an electric field or magnetic field can be applied to the material and adjusted to rotate the polarization of the light. Alternatively, wave plates or a polarizer can be used. These devices must be mechanically rotated in the path of the beam to change the polarization.  
         [0034]     This invention provides a transducer assembly that can be used with media requiring thermally assisted read back such as magnetic super resolution media, MAMMOS media and various exchange spring type media.  
         [0035]     While the invention has been described in terms of several examples, it will be apparent to those skilled in the art that various changes can be made to the disclosed examples without departing from the invention as set forth on the following claims.