Slider design

A slider is used in an optical or magneto-optical head having an optical assembly mounted on the slider body, for directing a read-write laser beam onto and from a data storage disk. The optical assembly includes an optical fiber a mirror a quarter wavelength plate, and a lens. The optical fiber guides the laser beam along an optical path defined by the optical assembly and the slider body. The laser beam emanating from the optical fiber impinges upon the mirror and is reflected thereby onto and through the quarter wavelength plate. The laser beam continues its travel along the optical path through the lens and a magnetic coil assembly onto the disk. The slider includes a channel pattern formed on its upper surface for positioning the optical components on the slider body. The channel pattern includes a plurality of channels that define an optical path, and a plurality of cavities formed along these channels for receiving various components such as optical, magnetic and electrical components.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to the field of data storage systems such as
 disk drives. The invention particularly relates to a slider design for use
 in an optical or magneto-optical read-write head for high density
 recording and reading of information onto and from a storage medium.
 2. Description of the Related Art
 Data storage systems such as those used with computer systems, typically
 store data magnetically or magneto-optically onto a storage medium. The
 data stored on the medium, whether magnetic or optical, is contained in
 spiral or concentric tracks. An optical data storage system described in
 U.S. Pat. No. 4,799,210 to Wilson, includes a laser diode assembly mounted
 on a fixed platform, and an optical head mounted on a movable stage. The
 laser beam is coupled to the movable head through a flexible optical
 fiber. Japanese patent application No. 59-117,180 describes another
 optical system mounted on the top or upper side of a slider.
 Efforts to reduce the size and weight of optical heads are represented by
 optical integrated circuits or thin film structures. U.S. Pat. No.
 4,911,512 to Yamamoto et al. describes a far-field type optical
 transducer, and a semi-conductor laser secured on a submount of silicon. A
 thin film silicon dioxide, SiO.sub.2, waveguide element and a glass
 waveguide layer are also fixed on the submount. A collimator lens, a beam
 splitter, and a focusing grating are formed on the glass waveguide layer.
 Another attempt to achieve compactness and weight reduction of a
 magneto-optical head is described in U.S. Pat. No. 5,199,090 to Bell. The
 Bell patent describes a magneto-optic head fabricated on a glass slider
 and flown adjacent a magneto-optical disk. A transducer is fabricated on
 an end of the glass slider. A planar or channel waveguide structure,
 fabricated by ion exchange in the end face of the glass slider, couples
 light from a light source, such as a laser diode, to the disk for reading
 or writing.
 Conventional magnetic read-write heads commonly utilize sliders as carriers
 for the magnetic assembly. These sliders are typically designed in
 compliance with the International Disk Drive Equipment and Material
 Association (IDEA) specifications. The following Table I illustrates
 conventional slider design characteristics that are not applicable yet to
 optical or magneto-optical sliders.
 TABLE I
 SLIDER DESIGN - IDEA SPECIFICATIONS
 Mini Slider Micro Slider Nano Slider Pico Slider
 Length 0.160 inch 0.112 inch 0.080 inch 0.049 inch
 (4064 .mu.m) (2845 .mu.m) (2032 .mu.m) (1245 .mu.m)
 Width 0.125 inch 0.088 inch 0.063 inch 0.039 inch
 (3175 .mu.m) (2235 .mu.m) (1600 .mu.m) (991 .mu.m)
 Height 0.035 inch 0.024 inch 0.017 inch 0.012 inch
 (889 .mu.m) (610 .mu.m) (432 .mu.m) (305 .mu.m)
 Optical heads present several slider design concerns. A first concern
 relates to the optical path of the optical assembly mounted on the slider.
 The optical path limits the ability to reduce the slider height,
 particularly if such a height forms part of the optical path. Another
 concern relates to the footprint (i.e., the projected surface area) of the
 slider, which should be sufficiently large to carry the optical assembly
 and the fibers mounted onto the slider, without affecting the aerodynamic
 flying performance of the optical head. Yet another consideration is the
 weight of the slider in light of the additional weight of the optical
 assembly and fibers.
 Another design concern is the overall weight of the optical head. It is a
 desirable objective to reduce the slider weight in order to improve the
 data access time. However, the slider design in an optical or
 magneto-optical read-write head is more involved than the slider design of
 a magnetic head, since additional features are needed to accommodate the
 slider optical components such as a lens, a mirror, optical fibers, and a
 field generating magnetic coil in the case to a magneto-optical recording
 head. These additional components augment the fabrication complexity of
 the slider design, and further increase the access time.
 For example, the pico slider might not be an effective aerodynamic platform
 because it is too small and light, causing the optical fiber stiffness to
 dominate the slider air bearing stiffness. The pico, nano and micro
 sliders might not be effective optical platforms because they are too
 thin, and probably would not meet the optical requirements of the head.
 The mini slider would satisfy the optical requirements of the head;
 however, the mini slider is too bulky and heavy, particularly with the
 added mass of the optical assembly.
 The continuing trend toward miniaturization of data storage systems is
 faced with the foregoing and other concerns, and cannot be accomplished by
 an arbitrary reduction in size and weight of the sliders.
 SUMMARY OF THE INVENTION
 According to the present invention, improvement is achieved in compactness
 and weight reduction of the slider design. The slider allows optical
 drives to achieve access time comparable to that of a magnetic head disk
 drive. Furthermore, the slider enables a more reliable head to disk
 interface system with an optical or magneto-optical plastic disk, and
 effects a lower gram load on the load beam and the slider. The slider of
 the present invention is reliable, and is compliant with the uneven
 topography of a rotating disk. The new slider design allows a relatively
 tight disk to disk spacing because of its z- height.
 The foregoing and other features of the present invention are realized by a
 new slider that directs a read-write laser beam onto and from a data
 storage disk. An optical assembly is mounted on the slider body, and
 includes an optical fiber, a mirror, a quarter wavelength plate, and a
 lens. The optical fiber guides the laser beam along an optical path
 defined by the optical assembly and the slider body. The laser beam
 emanating from the optical fiber impinges upon the mirror and is reflected
 thereby onto and through the quarter wavelength plate. The laser beam
 continues its travel along the optical path through the lens and a
 magnetic coil assembly onto the disk.
 The slider body is dimensioned to accommodate the physical size and weight
 of the optical assembly, as well as the working distance between a lens
 and the disk, along the optical path. The slider body is dimensioned to
 accommodate the dimensional constraints of the optical assembly. The
 slider has the approximate height of a mini slider, i.e., approximately
 889 .mu.m, and the planar footprint area corresponding to that of a nano
 slider, i.e., a length of approximately 2032 .mu.m and a width of
 approximately 1600 .mu.m. Several channels are formed in the slider to
 define an unobstructed optical path.

Similar numerals refer to similar elements in the drawings. It should be
 understood that the sizes and dimensions of the various components in the
 figures might not be in exact proportion, and are shown for visual clarity
 and for the purpose of explanation.
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIGS. 1 through 5 illustrate a slider 10 and an optical assembly 12 for use
 in an optical or magneto-optical head according to the present invention.
 With further reference to FIG. 4, and as it will be explained later in
 greater detail, the optical assembly 12 is mounted in part within the
 slider 10, for directing a read-write laser beam (or light beam) 14 onto
 and from a data storage medium, such as an optical or a magneto-optical
 disk 15.
 According to one embodiment of the present invention, the optical assembly
 12 includes a linearly polarized diode laser source (not shown) operating
 in a visible or near ultraviolet frequency region and emitting an optical
 power sufficient for reading and writing data onto and from the disk 15.
 The laser diode source may be a RF (radio frequency) modulated laser
 source. In an exemplary embodiment the linearly polarized laser source is
 selected to operate within a range of 635-685 nm; however, a laser source
 of other frequencies can alternatively be used.
 The optical assembly 12 includes an optical fiber 16, a mirror 20, a
 quarter wavelength plate 22, and a lens 24. The optical fiber 16 guides
 the laser beam 14 along an optical path defined by the optical assembly
 12. While only one optical fiber 16 is shown for the purpose of
 illustration, it should be clear that additional optical fibers or other
 light conveying means can alternatively be employed. The laser beam 14
 emanating from the optical fiber 16 impinges upon the mirror 20 and is
 reflected thereby onto and through the quarter wavelength plate 22. The
 laser beam 14 continues its travel along the optical path through the lens
 24 and a magnetic coil assembly 26 onto the disk 15.
 During the data writing phase, the laser beam 14 is routed by the optical
 assembly 12 to a magneto-optical recording layer 29 of the disk 15. The
 laser beam 14 lowers the coercivity of the magneto-optical layer 29 by
 heating a target spot 31 to a critical temperature, for example the Curie
 point of the magneto-optical layer 29. Preferably, the optical intensity
 of the laser beam 14 is held constant, while a time varying vertical bias
 magnetic field generated by a magnetic coil assembly 26 is used to define
 a pattern of "up" or "down" magnetic domains perpendicular to the disk 15.
 This technique is known as magnetic field modulation (MFM). As the
 selected spot 31 cools at the surface layer, information embodied in the
 laser beam 14 is encoded on the disk 15.
 During the data readout phase, the laser beam 14 (at a lower intensity
 compared to the laser beam used in the data writing phase) is routed by
 the optical assembly 12 to the disk 14. At any given spot of interest,
 i.e., 31, upon reflection of the laser beam 14 from the magneto-optical
 layer 29, the Kerr effect causes the reflected laser beam 14 to have a
 rotated polarization of either clockwise or counter clockwise sense that
 depends on the magnetic domain polarity at the spot 31.
 In the present embodiment, the optical path of the laser beam 14 is
 bi-directional. The reflected laser beam 14 is received through the
 optical assembly 14 and propagates along the optical fiber 16 to exit at
 one of its ends for subsequent conversion to an electrical signal.
 Additional operational details of the optical assembly 12 can found in
 U.S. Pat. No. 5,903,525, which is incorporated herein by reference.
 The slider 10 includes a body 11 which is dimensioned to accommodate the
 physical size and weight of the optical assembly 12, as well as the
 working distances along the optical path, between a forward end 33 of the
 optical fiber 16, the mirror 20, the lens 24 and the magneto-optical layer
 29 of the disk 15. The dimensions of the slider 14 do not strictly comply
 to industry standards (refer to Table I above). Rather, the slider 10 is
 dimensioned to accommodate the dimensional constraints of the optical
 assembly 12. In general, the height of the slider body 11 ranges, for
 example between approximately 876 .mu.m and approximately 902 .mu.m, and
 the slider body planar footprint ranges, for example between approximately
 1975 .mu.m.times.1552 .mu.m, and approximately 2089 .mu.m.times.1645
 .mu.m. In a preferred embodiment, the slider 10 has a height H (FIG. 4)
 about that of a mini slider, i.e., approximately 889 .mu.m, and the planar
 footprint area corresponding to that of a nano slider, i.e., a length L of
 approximately 2032 .mu.m and a width W of approximately 1600 .mu.m (FIG.
 2).
 With further reference to FIG. 2, the optical fiber 16 is secured to the
 slider 10 along a fiber channel (also referred to as the first channel) 40
 formed on or within the upper surface (i.e., top) of the slider 10, and
 extends along substantially the entire length of the slider 10.The channel
 40 is sufficiently wide to receive the optical fiber 16. The width w1 of
 the first channel 40 ranges, for example between approximately 114 .mu.m
 and approximately 140 .mu.m. In a preferred embodiment the width w1 is
 approximately 127 .mu.m. The optical fiber 16 is placed within the channel
 40, in a recessed position, and the channel 40 is filled with an
 ultraviolet curing epoxy or similar adhesive material to secure the
 optical fiber 16 to the slider 10.
 The channel 40 terminates at its forwardmost end 42 in an opening 43A (FIG.
 1) which is relatively larger in size than the width w1 of the fiber
 channel 40. Although, in a preferred embodiment the fiber channel 40 is
 located in proximity to a longitudinal side 43 of the slider 10, a person
 of ordinary skill in the art will recognize that the fiber channel 40 can
 be located at other positions on the slider 10, for example, between the
 longitudinal side and a central axis or, alternatively, along the central
 axis itself.
 A transverse channel 44 (also referred to as adhesive stop channel) extends
 at an angle relative to the fiber channel 40. In a preferred embodiment,
 the transverse channel 44 is substantially perpendicular to the fiber
 channel 40, across substantially the entire width of the slider 10. The
 fiber channel 40 crosses the transverse channel 44 at an edge 41. The
 width w2 of the transverse channel 44 is, for example approximately 127
 .mu.m. The transverse channel 44 acts as a stop for the adhesive material
 within the fiber channel 40, to prevent the adhesive material from flowing
 to the mirror 20 and affecting the integrity of the optical path. Thus,
 excess adhesive material is allowed to flow into the transverse channel
 44. Although, in a preferred embodiment the transverse channel 44 is
 located in proximity to a trailing edge or side 51 (FIG. 1) of the slider
 10, a person of ordinary skill in the art will recognize that the
 transverse channel 44 may be located at other positions on the slider 10.
 The forward end 33 of the optical fiber 16 projects in part within the
 transverse channel 44, and is raised above the bottom 45 (FIG. 4) of the
 transverse channel 44 to prevent excess adhesive material from flowing
 against, and obstructing the path of travel of the laser beam 14. The
 forward end 33 is directed toward the mirror 20, and is positioned at a
 predetermined distance therefrom. The laser beam 14 emanating from the
 fiber 16 traverses the forward portion 46 of the fiber channel 40 and
 impinges upon a target field 50 on the mirror 20, along an unobstructed
 path. To this end, the transverse channel 44 prevents the adhesive
 material from flowing into the forward portion 46 of the fiber channel 40.
 The forward end 33 of the optical fiber 16 is positioned at an optical
 path distance "a" from the target field 50 of the mirror 20. In one
 embodiment the distance "a" is approximately 450 .mu.m, though this value
 can vary in other embodiments.
 Considering now the trailing edge 51 of the slider 10, it is formed of a
 flat slanted or angled surface 55 (FIG. 1) upon which the mirror 20 is
 mounted. The mirror 20 deflects the laser beam 14 from the optical fiber
 16 toward the lens 24. In a preferred embodiment, the slanted surface 55
 is disposed at an angle of approximately 45 degrees, so that the light
 beam 14 is reflected at a right angle by the mirror 20 (FIG. 4).
 With reference to FIGS. 1, 3 and 4, the trailing edge 51 also includes an
 upright or vertical channel 60 which is in optical communication with the
 fiber channel 40, for housing the lens 24, and for defining a portion of
 the optical path along which the laser beam 14 travels. The width of the
 vertical channel 60 ranges, for example between approximately 214 .mu.m
 and approximately 240 .mu.m, and is preferably approximately 227 .mu.m.
 The center line 64 of the optical path is co-aligned with the focal axis
 of the lens 24 (FIG. 3), and is positioned at a distance of approximately
 803 microns from the longitudinal side 43 of the slider 10.
 The trailing edge 51 further includes a lateral channel 70, disposed at
 approximately the center of the trailing edge 51 (FIG. 1) for receiving
 the quarter wavelength plate 22. The lateral channel 70 lies in a plane
 that is generally normal to the planes of the fiber channel 40 and the
 vertical channel 60. The lens 24 is fitted within the vertical channel 60
 underneath the quarter wavelength plate 22 to achieve focus of the laser
 beam 14 as a focused optical spot 31. According to another embodiment, the
 lens 24 is fitted within the lateral channel 70 along the path of travel
 of the laser beam 14. The bottom of the lens 24 is slightly recessed
 relative to the air bearing surface 77 defined by the twin rails 80, 82
 (FIG. 5) of the slider 10. A relief 83 (FIG. 5) is formed between the two
 rails 80, 82. The magnetic coil assembly 26 is secured to the bottom of
 the lens 24 (FIG. 4), and has a thickness "t1" of, for example
 approximately 31 .mu.m. After the slider 10 and the optical assembly 12
 are assembled, the upper surface of the slider 10 is secured to a
 suspension. Two peripheral grooves 53 are formed along the two opposite
 sides 43 to simplify the assembly of the optical components onto the
 slider 10.
 With reference to FIG. 4, and according to one embodiment of the present
 invention, the lens 24 is a GRIN lens. The lens 24 includes at its bottom
 end a planar surface and at the opposite end a convex surface with a
 radius of curvature of approximately 190 .mu.m. The lens 24 has a diameter
 of approximately 250 .mu.m, and a length of approximately 329 .mu.m. An
 optical path length "b" from the target field 50 of the mirror 20 to the
 convex surface of the lens 24 is approximately 443 .mu.m. While one
 exemplary embodiment of the lens 24 has been described, it will be
 appreciated that other types and geometries of the lens 24 are possible.
 The optical assembly 12 presents constraints on the slider height. For
 instance, the optical assembly 12 should generate a small enough spot 31
 on the disk 15. If the slider height "H" is excessive, the slider center
 of gravity will shift upward, affecting the head stability, and reducing
 the access time.
 In one embodiment the mirror 20 is a steerable micro-machined mirror
 assembly, and includes a generally 300 .mu.m square reflective target
 field 50. Fine tracking and short seeks to a series of nearby tracks may
 be performed by rotating the reflective target field 50 about a rotation
 axis so that the propagation angle of the laser beam 14 is changed before
 transmission to quarter wavelength plate 22. The reflective target field
 50 is rotated by applying a differential voltage to a set of drive
 electrodes. The differential voltage on the electrodes creates an
 electrostatic force that rotates the reflective target field 50 about a
 set of axial hinges (not shown), and enables the focused optical spot 31
 to be moved in the radial direction of the disk 15. Wires 50A are
 connected to the mirror 20 for providing dithering and other control
 signals. The mirror 20 may include a piezzo-electric element that enables
 the dithering for fine tracking of the laser beam 14.
 The magnetic coil assembly 26 may be of the type described in U.S. Pat.
 application titled "Magnetic Coil Assembly", Ser. No. 08/844,003, filed on
 Apr. 18, 1997.
 Those skilled in the art will recognize that positioning the optical
 assembly 12 at other than along the central axis of the slider 10 may
 affect the center of mass of the head, and thus its flying dynamics.
 Accordingly, the point of attachment of the head to a suspension (not
 shown), may require adjustment to compensate for off-center changes in the
 center of mass of the head. In one embodiment, the channels 40, 44, 60, 70
 are designed as V-grooves, or any other suitable channels for coupling the
 optical assembly 12 to the slider 10 and for aligning it relative to the
 suspension and the disk 15.
 With reference to FIG. 5, the rails 80, 82 define the positive pressure air
 bearing surface 77 of the slider 10, and do not extend along the entire
 length of the slider 10. This enables the slider 10 to accommodate the
 optical assembly 12 and the higher frequency of axial modulation around
 the disk 15. In an exemplary embodiment, the length "I" of each rail 80,
 82, including its corresponding taper 87, 88 is, for example approximately
 1,701 .mu.m. The length of each taper 87, 88 is, for example approximately
 203 .mu.m. In operation, the plane of the air bearing surface 77 is for
 example approximately 0.4 .mu.m from the upper surface of the rotating
 disk 15.
 The width of the symmetrical rails 80, 82 is preferably increased over
 those of conventional sliders, in order to compensate for the relatively
 short rail length and to provide the required air bearing surface. An
 exemplary width "w2" of the rails 80, 82 and that of the tapers 87, 88 is
 approximately 460 .mu.m. While the slider 10 has been described as having
 the footprint of a nano slider and the height of a mini slider, it should
 be understood that other size variations are possible provided they meet
 the physical and the optical path length requirements of the optical
 assembly 12, without compromising the aerodynamic performance of the head.
 For illustration purpose, each rail has its width to length ratio ranging
 between approximately 0.26 and approximately 0.28, with a more preferred
 value of approximately 0.27.
 The slider 10 is a platform that acts as a carrier to mount optical
 components as well as writing field components onto a slider for optical
 recording or MO (magneto-optical) recording.
 FIG. 6 illustrates the slider 10 of the present invention and a
 conventional slider 85 flying over the disk 15. The disk 15 can be made of
 plastic material and as a result, its microscopic surface is typically
 foil shaped and irregular. Plastic disks usually present excessive warpage
 compared to aluminum or glass disks, but allow servo patterns to be easily
 and inexpensively stamped.
 To illustrate, the plastic disk 15 shown in FIG. 6 may have an undulation
 period T (i.e., the distance between two successive peaks or valleys) of
 approximately 8,000 .mu.m, that is about twice the length of a
 conventional mini slider 85. As it can be appreciated, the conventional
 slider 85 does not effectively negotiate the wavy surface of the disk 15,
 and may lead to head crashes. On the other hand, the slider 10 of the
 present invention has about one half the length of the mini slider 85 and
 can effectively "ride.smallcircle. or negotiate the surface of the disk
 15, thus effectively minimizing head crashes. In certain embodiments, the
 length of the slider body 11 ranges between approximately 25 percent and
 approximately 75 percent of the undulation period T.
 The slider 10 may be obtained by slicing a wafer into a plurality of
 individual die, with the channels 40, 44, 60 and 70 formed in at least
 some of the die. The slider 10 can be made of hard material such as
 titanium carbide. Alternatively, the slider 10 may be prefabricated or
 molded from calcium titanate or another suitable material, either
 individually, or sliced from a row bar of sliders. In other embodiments,
 the slider 10 may be formed of suitable material such as silicon, by
 various available techniques such as hot isostatic press process (HIP),
 reactive etching, ion beam etching, or other etching or machining
 processes.
 FIG. 7 shows a molded slider 110. By molding the slider 10 it is now
 possible to achieve complex geometrical slider designs in a single molding
 process, since the a manufacturing complexity is transferred to the
 reusable mold design. Another aspect of the molding process is that
 cavities or vias 115, 117 can be formed inside or on the surface of the
 slider 10, to further reduce the slider mass, for faster access time and
 also to reduce the electrical current requirements to drive the HGA
 actuator, since a lower slider mass significantly affects the polar moment
 of inertia of head. Moreover, for positive pressure air bearing designs
 such as the twin taper flat illustrated in FIG. 5, specific geometries can
 be achieved by the molding process.
 Another advantage of forming cavities within the slider 10 is the ability
 to optimize the location of the slider center of gravity to account for
 the optical assembly 12 loaded thereon. While only two cavities 115, 117
 are shown, it should be understood that additional cavities can be formed,
 patterned, and distributed throughout the slider volume.
 With further reference to FIGS. 4, 5 and 10, they illustrate a stepped
 groove 120 formed in the underside of the slider 10 in proximity to the
 trailing edge 51. The coil assembly 26 is disposed within the groove 120,
 where it is secured to the lens 24 and the air bearing surface 77 of the
 slider 10 by means of an adhesive layer 121. The groove 120 has a depth
 "d" that ranges for example between approximately 15 microns and
 approximately 45 microns, and preferably between approximately 28 microns
 and approximately 31 microns. The groove 120 simplifies the precise
 positioning and alignment of the lens 24 and the coil assembly 26 relative
 to the air bearing surface 77.
 FIG. 8 is an exploded, perspective view of another slider 10A according to
 the present invention. Slider 10A is substantially similar in design and
 function to the slider 10, with the lateral channel 70 being dimensioned
 to receive one or more additional optical components such as a lens 124.
 To this end, the optical component or lens 124 can be mounted on a carrier
 122 which is inserted within, and secured to the lateral channel 70.
 Carrier 122 provides a convenient way for handling the optical components
 mounted thereon, and is preferably flat. The carrier 122 can be made of
 the same material as the slider 10. The width of the lateral channel 70
 can vary between approximately 150 microns and approximately 400 microns,
 and preferably between approximately 242 microns and approximately 292
 microns.
 In yet another embodiment, the slider 10A includes one or more additional
 lateral channels 170 (shown in dashed lines) within which one or more
 carriers (similar to carrier 122) or optical components (similar to the
 quarter wavelength plate 22) are inserted.
 FIG. 9 is a top plan view of another slider 140 showing an alternative
 channel configuration or pattern formed on the top or upper surface of the
 slider body 11, for securing various optical, magnetic and/or electrical
 components on the slider 140. In the example illustrated in FIG. 9 the
 channel configuration includes a plurality of channels 142, 143, 144, 145
 along which a plurality of cavities 146, 147, 148, 149, 150, 151, 152,
 153, 154 are formed to receive and retain various optical, electronic, or
 other components along the optical path, or to regulate the optical path
 of the laser beam or beams 14. For illustration purpose, a splitter or
 reflective surface 160 (shown in dashed lines) is disposed, aligned, and
 secured within the cavity 152 to split or reflect the laser beam 14. The
 dimensions of the channels 142, 143, 144, 145 and the cavities 146, 147,
 148, 149, 150, 151, 152, 153, 154 can be selected for optimal performance
 of the head incorporating the slider 140.
 FIG. 11 is a top plan view of yet another slider 180 showing an alternative
 channel configuration for securing various optical and/or components on
 the slider 180. In this example, the channel configuration is generally
 similar to the channel configuration of slider 140 (FIG. 9), but further
 includes an additional trailing edge opening 43B which is similar to
 opening 43A, and another channel 182 that connects the splitter 160 to the
 opening 43B. An optical component such as a prism or a lens 184 (shown in
 dashed lines) can be disposed along channel 182. It should be understood
 that the channel configurations of FIGS. 1, 9 and 11 are shown only for
 illustration purpose, and that other channel configurations are possible.
 For example, in one channel configuration the enlarged opening 43A is
 replaced with another opening 243A (shown in dashed lines) having
 approximately the width of the cavity 146 (FIG. 11) or the width of the
 fiber channel 40 (FIG. 1).
 FIG. 12 illustrates a disk drive 210 comprised of a head stack assembly 212
 and a stack of spaced apart optical or MO data storage disks or media 15
 that are rotatable about a common shaft 215. The head stack assembly 212
 is rotatable about an actuator axis 216 in the direction of the arrow C.
 The head stack assembly 212 includes a number of actuator arms, only three
 of which 218A, 218B, 218C are illustrated, which extend into spacings
 between the disks 15.
 The head stack assembly 212 further includes an actuator block 219 and a
 magnetic rotor 220 attached to the block 219 in a position diametrically
 opposite to the actuator arms 218A, 218B, 218C. The rotor 220 cooperates
 with a stator (not shown) for rotating in an arc about the actuator axis
 216. Energizing the coil of the rotor 220 with a direct current in one
 polarity or the reverse polarity causes the head stack assembly 212,
 including the actuator arms 218A, 218B, 218C, to rotate about the actuator
 axis 216 in a direction radial to the disks 15.
 A head gimbal assembly (HGA) 228 is secured to each of the actuator arms,
 for instance 218A. The HGA 228 comprises a resilient load beam 233 and a
 slider, such as one of the inventive sliders described herein, secured to
 the free end of the load beam 233. The slider is also referred to herein
 as a support element since it supports an optical assembly 12 and/or the
 electromagnetic coil assembly 26. The optical assembly 12 is secured to
 the HGA 228 and in particular to the slider for providing the required
 optical reading and writing beams.
 FIG. 13 illustrates a magneto-optical (MO) storage device 1000 according to
 the present invention. The magneto-optical storage device 1000 includes a
 flying magneto-optical (FMO) head 1170 technology with Winchester-type
 rotary actuator arms 1160 and a suspension 1165. In a preferred
 embodiment, the MO storage device 1000 includes a laser-optics assembly
 1110, a Single-Mode Polarization Maintaining (SMPM) optical fiber 1130, a
 phase compensator 1120, a fiber optic switch 1150, an actuator magnet and
 coil 1145, a plurality of SMPM optical fibers 1140, a plurality of arms
 1160, a plurality of suspensions 1165, a plurality of MO storage media
 1180, and a plurality of FMO heads 1170.
 Each of the MO storage media 1180 is mounted on a spindle 1185 for
 continuous rotation at a constant angular velocity. Each of the FMO heads
 1170 is preferably attached via a suspension 1165 and a head arm 1160 to
 the electromagnetic actuator magnet and coil 1145. Those skilled in the
 art will recognize that the MO storage device 1000 may comprise as few as
 one MO head 1170 and one MO storage medium 1180, or an upper and lower FMO
 head 1180 for a plurality of MO storage media 1180.
 With further reference to FIG. 14 the laser/optics assembly 1110 includes a
 laser optical source such as a laser diode 1251, and a differential
 photodiode detector system and associated optical components, either as
 separate components, or alternatively as hybrid integrated circuit
 components. In a preferred embodiment, the laser diode 1251 is a polarized
 optical light source such as a 30-40 mW laser diode or a diode-pumped
 micro-chip laser operating in the visible or near ultraviolet region
 (preferably in the vicinity of 635 nm). The laser/optics assembly 1110
 further includes a leaky beam splitter 1245, collimating optics 1250
 disposed intermediate the laser diode 1251 and the leaky beam splitter
 1245, and a coupling lens 1240, such as a Gradient Refractive Index (GRIN)
 lens that focuses the outgoing optical beam from the leaky beam splitter
 1245 into a Single-Mode Polarization-Maintaining (SMPM) optical fiber 1130
 feed.
 In the present exemplary embodiment a phase compensator 1120 is used to
 compensate for relative phase fluctuations that occur between the inherent
 dual polarization modes of each of the polarization-maintaining optical
 fibers 1130 and 1140 (FIG. 13). Each of the polarization modes of the
 optical fibers 1130 and 1140 experiences different refractive indices
 because of the inherent birefringence of the fibers 1130 and 1140. For
 example, relative phase fluctuations may arise because of a slight
 variation in a difference between the two refractive indices caused by
 changes in temperature, pressure, and mechanical motion of each of the
 optical fibers 1130 and 1140. These fluctuations may be sensed by the
 laser-optics assembly 1110, and before significant changes occur, a
 feedback servo (not shown) adjusts the phase compensator 1120 to cancel
 the fluctuation. In this way, an optical path formed by the optical fibers
 1130 and 1140, to and from the flying MO head 1170, my be treated similar
 to a free-space optical path in terms of its polarization properties.
 In a preferred embodiment the phase compensator 1120 includes a
 piezoelectric cylindrical shell preferably made of a piezoelectric
 material such as lead zirconate titanate, to form a phase modulator. The
 phase compensator 1120 has a height preferably less than its diameter to
 provide a low-profile shape suitable for use in a compact magneto-optical
 storage system with reduced electrical capacitance for faster operation.
 The optical fiber 1130 may be attached to the circumference of the phase
 compensator 1120 with an ultraviolet-caring epoxy or another suitable
 adhesive. Metal electrodes are deposited on flat ends of the cylindrical
 shell to reduce the capacitance so that a voltage applied across the
 electrodes induces an expansion of the shell in a radial direction,
 thereby stretching the optical fiber 1130. The stretching action serves to
 provide phase modulation.
 In order to minimize the mechanical stress on the optical fiber 1130, the
 diameter of the phase compensator 1120 is preferably greater than a few
 hundred times the cladding diameter of the optical fiber 1130. For
 example, a fiber cladding diameter of approximately 80 microns corresponds
 to a phase compensator 1120 diameter in the vicinity of 10 nm to 40 nm.
 In the present exemplary embodiment, the fiber optic switch 1150 (FIG. 13)
 accepts the SMPM optical fiber 1130 at an input port and routes the
 optical beam emanating from this fiber 1130 to one of the SMPM optical
 fibers 1140 at an output port. The switching properties of the fiber optic
 switch 1150 are bidirectional so that the optical beam propagating back to
 the switch 1150 along any one of the SMPM optical fibers 1140 at the
 output port may also be routed to the optical fiber 1130 at the input
 port.
 The SMPM optical fibers 1140 from the fiber optic switch 1150 are
 preferably routed along respective head arms 1160 and suspensions 1165 to
 respective FMO heads 1170. In the preferred embodiment, there is one SMPM
 optical fiber 1140 for each FMO head 170, and the fiber optic switch 1150
 is used to select the MO head 1170 is active for reading data from, or
 writing data on the MO storage medium 1180.
 During the writing phase, light is delivered through an individual optical
 fiber 1140 to a respective FMO head 1170 for the purpose of focally
 heating a respective surface of a rotating MO storage medium 1180, thereby
 producing a "hot spot". A magnetic coil secured to, or formed on the FMO
 head 1170 is used to produce a magnetic field, which, in turn, magnetizes
 the region within the hot spot with a vertical orientation either "up or
 down". Thus, as the MO storage medium 1180 rotates, the applied magnetic
 field is modulated so as to encode digital data as a pattern of "up or
 down" magnetic domain orientations.
 During the readout phase, a polarized light beam 14 at a lower intensity is
 delivered through an SMPM optical fiber 1140 to a respective FMO head 1170
 for the purpose of probing or scanning the rotating storage medium 1180
 with a focused optical spot. Readout is performed in such a way that the
 magnetization direction of the MO storage medium 1180 at the location of
 the focused spot alters an optical polarization of the light beam 14 via
 the magneto-optical Kerr effect. In this way, the pattern of "up or down"
 magnetization orientations representative of the stored digital data
 modulates the polarization of the light beam 14 reflected from the MO
 storage medium 1180. The reflected light signal from the MO storage medium
 1180 then couples back through the FMO head 1170, one of the plurality of
 SMPM optical fibers 1140, and the fiber optic switch 1150, finally
 reaching two photodiode detectors 1215 for conversion into electronic
 format by a differential amplifier 1210.
 Referring now to FIG. 15, each FMO head 1170 includes a slider body (or
 slider) 1330. The FMO head 1170 further includes a groove or channel 1360,
 a steerable micro-machined mirror 1340, and a magnetic coil 1310. The
 groove 1360 can for example be V-shaped for retaining a SMPM fiber 1350.
 With further reference to FIGS. 16 and 17, the FMO 1170 utilizes the air
 bearing surface (ABS) 1510 of the slider 1330 that flies above or below a
 coated upper surface of the MO storage medium 1180. A polarized beam of
 laser light is transmitted through the SMPM optical fiber 1350 to the
 mirror 1340. The axis of the V-groove 1360, and hence the axis of the
 fiber 350 lying in the groove 1360, is substantially parallel to the
 medium 1180 surface. Light exiting the fiber 1350 is reflected by the
 mirror 1340 at an average angle of approximately ninety degrees relative
 to the axis of the optical fiber 1350.
 The reflected light is directed through an embedded micro-objective lens
 such as a GRIN lens 1420. Fine tracking and short seeks to adjacent tracks
 are performed by rotating the mirror 1340 about a rotation axis 1410
 (shown in FIG. 16). In this way a focused optical spot 1440 (FIG. 16) is
 scattered back and forth in a direction 1520 (illustrated as an arrow in
 FIG. 17) which is substantially parallel to the radial direction of the
 medium 1180. As the actuator arm 1160 moves the slider body 1330 back and
 forth across the surface of the medium 1180, the position of the slider
 body 1330 may become skewed slightly such that the direction 1520 is not
 precisely parallel to the radial direction of the MO storage medium 1180.
 Although not precisely parallel, the skew angle is sufficiently small that
 a substantial component of the scanning direction 1520 lies along the
 radial direction of the storage medium 180.
 FIG. 18 illustrates the light path through an exemplary lens 1420 of the
 present invention. The light beam 14 is reflected from the 1340 is
 collected by a focusing optic comprising an objective GRIN lens 1420 that
 focuses the reflected light beam 14 onto the surface of the storage medium
 1180.
 The position of the optical fiber 1350 within the groove 1360 may be
 adjusted, thereby changing the distance from the end of the SMPM optical
 fiber 1350 to the mirror 1340. Relocating the position of the SMPM optical
 fiber 1350 within the groove 1360 effectively adjusts the location of the
 focal point 1440 of the light beam 14. Once the fiber 1350 is positioned
 for proper focus on the surface of the medium 1180, the fiber 1350 may be
 secured in place by means of ultraviolet (UV) curing epoxy or similar
 adhesive.
 The use of a cylindrically shaped GRIN lens 1420 allows the lens 1420 to be
 inserted easily into the vertical channel 60 the slider body 1330. To
 minimize spherical aberrations and to achieve diffraction-limited
 focusing, the lens 1420 is polished to assume a plano-convex shape with
 the convex surface 1650 being a simple spherical shape. The height L.sub.H
 1640 of the lens 1420 depends on a number of factors including the
 magnitude of the refractive index gradient, the wavelength of the light
 beam, the numerical aperture of the SMPM fiber 1350, and the desired size
 of the focused optical spot 1440 as determined by the effective numerical
 aperture of the lens 1420. In a preferred embodiment, the lens height
 L.sub.H 1640 ranges between approximately 170 microns and approximately
 500 microns, the lens radius of curvature ranges between approximately 150
 microns and approximately 400 microns, and the lens diameter L.sub.D
 ranges between approximately 200 microns and approximately 500 microns.
 While the FMO head 1170 illustrated in FIGS. 15 through 17 is shown to
 include a GRIN lens 1420, it will be appreciated by those skilled in the
 art that additional objective optics can also be used to enhance the
 properties of the lens 1420. For example, the focusing objective optics
 may include either an aplanatic lens or a solid immersion lens in
 conjunction with the GRIN lens 1420. The use of such an additional lens
 element can achieve a larger numerical aperture and hence a smaller size
 focused optical spot 1440. A smaller spot size permits higher areal data
 densities to be written to and from the MO storage medium 1180.
 Micro-optic lenses made by molding glass or plastic can be used in place of
 the GRIN lens 1420. For example, two molded plano-convex aspherical lenses
 can be combined by placing the two convex surfaces toward each other to
 provide a miniature lens component with high numerical aperture and good
 off-axis performance as the mirror 1340 is rotated or moved. In a dual
 aspherical optical design, the light beam 14 is substantially collimated
 between the two optical elements, allowing a quarter wave plate to be
 placed between the two elements without additional lenses.
 In another embodiment, a single spherical lens with low numerical aperture
 (i.e., 0.2-0.4) may be used in conjunction with an aplanatic or solid
 immersion lens to yield an optical focusing system with a relatively high
 numerical aperture (i.e., greater than 0.6).
 From a manufacturing perspective, molded lenses are attractive because they
 can be mass produced at low cost. One such mass production method involves
 molding a lens array and subsequently sectioning the array by diamond saw
 cutting or laser cutting to obtain Individual lenses. Regarding the
 aforementioned two-lens design, two molded plano-convex lens arrays may be
 secured together by means of tapered fittings before sectioning, to ensure
 accurate lens alignment.
 According to another preferred embodiment of the present invention the
 micro plano-convex GRIN lens 1420 is made by polishing a conventional a
 plano-plano GRIN rod lens so as to provide a convex surface at the planar
 end of the GRIN rod lens. In an exemplary embodiment, the objective lens
 1420 is a cylindrical plano-convex GRIN lens that includes at a bottom end
 a piano surface 1421 and at an opposite end a convex surface 1650 with a
 radius of curvature of approximately 190 microns. As compared to
 conventional GRIN lenses, the cylindrical and planar portions of the
 present GRIN lens 1440 improve the ability to align an optical axis of the
 lens 1440 relative to the optical path (FIG. 18) of the flying MO head
 1170. The use of a single optical element GRIN lens 1420 eliminates the
 requirement for alignment of multiple objective optic elements relative to
 each other. In an exemplary embodiment, the diameter L.sub.D of the GRIN
 lens 1420 diameter is approximately 250 microns, and the height L.sub.H of
 the GRIN lens 1420 is approximately 329 microns. An optical path length
 D.sub.p from a center point 1660 of the mirror 1340 to the convex surface
 1650 of the GRIN lens 1420 is approximately 435 microns.
 The SMPM optical fiber 1350 has a numerical aperture of approximately 0.15.
 The distal end of the SMPM optical fiber 1350 is positioned at a distance
 D.sub.S of approximately 450 microns from the center point 1660 of the
 mirror 1340. The distance D.sub.D from the piano surface 1421 of the lens
 1420 to the focal point 1440 is approximately 25 microns.
 As discussed herein, the present invention uses a GRIN lens 1420
 manufactured to very small dimensions. The optical and geometrical
 properties of the lens 1420 permit its mounting on a bottom surface of the
 FMO head 1170 or, alternatively, on or near other optical or magnetic
 components so as not to interfere with the aerodynamic flying qualities of
 the FMO head 1170.
 With further reference to FIG. 19, the magnetic coil assembly 26 is
 positioned below the GRIN lens 1420 as part of the FMO head 1170. The
 magnetic coil assembly 26 generates a magnetic field with a component in a
 direction normal (i.e., perpendicular) to the MO storage medium 1180. A
 vertical channel 1740 (corresponds to the vertical channel 60 in FIG. 1)
 into which the lens 1420 is inserted, is etched in the slider body 1330.
 During fabrication, the depth and diameter of the vertical channel 1740 is
 made to provide an unobstructed optical path to the light beam 14.
 The vertical channel 1740 is patterned to include a conical portion 1744
 with a cone angle approximately equal to that of the focused cone of the
 polarized light beam 14, for example approximately 37 degrees in
 half-angle for a numerical aperture of 0.6. In this way, a shelf 1730 is
 formed for supporting the lens 1420 while also allowing a planar magnetic
 coil assembly 26 to be deposited within a recessed area which is etched on
 the bottom side of the shelf 1730. In a preferred embodiment, the diameter
 of conical portion 1744 is sufficiently large to accommodate off-axis
 steering of the polarized light beam 14.
 FIG. 20 illustrates a preferred embodiment of the mirror 1340. The mirror
 1340 is a torsional mirror comprising a silicon substrate 1810, drive
 electrodes 1825, 1830, bonding pads 1815, 1820, a bonded silicon plate
 1850, and a thin film flexure layer 1845 made from a material such as
 silicon dioxide, silicon nitride, or silicon. The mirror 1340 may be
 fabricated using micromachining techniques to yield a reflective inner
 torsional reflective area 1835 comprising the flexure layer 1845 on top
 and a silicon plate layer 1855 on the bottom for mechanical rigidity, and
 supported by two flexure layer hinges 1840.
 The reflective area 1835 may be metallized with gold or a similar substance
 to increase the optical reflectivity and to improve the electrostatic
 actuation of the mirror 1340. In a preferred embodiment, the mirror 1340
 has a resonant frequency in the range from approximately 50 kHz to 200
 kHz, as determined by the particular geometry and material properties of
 the mirror 1340. The mirror 1340 has a generally square shape with outer
 linear dimensions in the range from approximately 100 microns to 170
 microns, and a thickness ranging from approximately 2 microns to
 approximately 50 microns.
 The inner reflective area 1835 has an approximate outer linear dimension in
 the range from approximately 25 microns to approximately 200 microns, and
 a thickness of approximately 1 micron to approximately 20 microns.
 Preferably, the mirror 1340 may be driven torsionally without any
 excessive transverse motion.
 In an exemplary embodiment, the side of the reflective area 1835 is
 preferably on the order of 100 microns. The resonant frequency of the
 reflective area 1835 is preferably greater than 100 kHz, and the maximum
 physical angular deflection is preferably 2 degrees. In addition, the
 mirror 1340 should preferably not warp either statistically or dynamically
 upon actuation and the maximum stress upon electrostatic deflection should
 preferably be well below the expected yield stress of the material used to
 construct the mirror 1340 (for example: silicon, silicon dioxide, silicon
 nitride, and aluminum).
 The mirror 1340 is operated by applying a differential voltage to the drive
 electrodes 1825, 1830, which differential voltage results in an
 electrostatic force on the reflective area 1835. The reflective area 1835
 rotates about the hinges 1840, enabling the reflected light beam to be
 directed and scanned back and forth about the surface of the medium 1180.
 A more detailed description of the operation of the mirror 1340 will be
 discussed hereafter, with further reference to FIG. 22.
 Referring now to FIG. 21, it illustrates a FMO head 1170 that includes a
 slider body 1330 and a mirror support 1910. The mirror support 1910
 includes two electrode pads 1915, 1920 that provide electrical contact
 points for the application of a differential voltage to the corresponding
 bonding pads 1815,1820 of the mirror 1340. The mirror support 1910
 additionally includes access holes 1925, 1930 that provide an unobstructed
 optical path from the SMPM optical fiber 1350, to the mirror reflective
 area 1835 (FIG. 20) and to the lens 1420.
 The mirror support 1910 provides the mirror 1340 with a 45 degree support
 surface. Those skilled in the art will understand that the mirror support
 1910 may be attached to the slider body 1330 and may be manufactured using
 any number of techniques. For example, the slider body 1330 can be
 micromachined and the mirror support 1910 can be made separately and then
 bonded to the slider body 1330. According to another embodiment, a 45
 degree angle may be created using other techniques such as leaning the
 mirror 1340 against a suitably dimensioned slider 1330 having suitably
 dimensioned steps 1940, 1945.
 Referring now In FIG. 22 the mirror 1340 is shown mounted to the mirror
 support 1910. The application of a differential voltage to the electrode
 pads 1915, 1920 steers the light beam 14 supplied by SMPM optical fiber
 1350. The mirror 1340 is used to change the propagation angle of the light
 beam 14 before transmission to the lens 1420. The movement of the
 resultant focal point 1440 along the radial direction 1520 (FIG. 17) of
 the storage medium 1180 is used for track following, as well as for short
 seeks from one data track to another. Track following may be accomplished
 by using combined coarse and fine tracking servo techniques.
 A sampled sector servo format may be used to define the tracks. These servo
 marks may include either embossed pits stamped into the medium 1180 or
 magnetic marks read similar to the data marks. In the case of embossed
 pits, those skilled in the art will recognize that the differential
 amplifier 1210 (FIG. 14) output of the laser optics assembly 1110 (FIG.
 14) should be substituted by an adder circuit. Coarse tracking may be
 maintained by continuously adjusting a current to an actuator coil (part
 of the actuator magnet and coil 1145 shown in FIG. 13) for controlling the
 position of the suspension 1165 while fine trucking may be accomplished by
 continuously adjusting the angular deflection of the mirror 1340. The
 slider 1330 is secured to the suspension 1165 by means of a flexure 1166.
 The use of the steerable micro-machined mirror 1340 is advantageous because
 it offers a method for a very fast manipulation of an optical beam 14.
 This approach facilitates high-speed track following and short seeks for
 much improved data access times. Such improvements over conventional head
 technology make possible high areal densities by enabling the use of very
 narrow track pitches.
 The FMO head 1170 design is intrinsically confocal in nature. During
 readout, the light beam reflected from the MO storage medium 1180 is
 coupled back into the SMPM optical fiber 1140 which acts as the aperture
 in a confocal system. One of the benefits arising from the use of confocal
 optics includes very high depth resolution along the optical axis as well
 as improved transverse resolution. Another advantage of the confocal
 system is that light reflected from objective optics surfaces is not
 collected so that anti-reflection coating may not be necessary. This is
 particularly advantageous in a design that uses an aplanatic lens and a
 non-zero working distance. The high depth resolution allows for very close
 spacing of the layers in a multi-layer medium with low crosstalk between
 layers, while the improved transverse resolution provides detection of
 smaller storage medium marks and sharper storage medium mark edges than
 would otherwise be the case in a non-confocal system.
 The FMO head 1170 design illustrated herein is representative of one
 approach for storing information on high-density MO storage media 1180. It
 will be appreciated by those skilled in the art that various variations of
 the present invention may be implemented to achieve substantially the same
 goals. For example, various types of fiber optical switches (e.g.
 micro-mechanical, electro-optical, thermo-optical) may be utilized. In
 addition, the flying FMO head 1170 design my be modified for use with a
 free space optical input beam, thereby eliminating optical fibers 1140.
 Also, the focusing objective lens does not need to be limited to a GRIN
 lens 1420 because other micro-objective lenses, such as molded aspheres,
 holographic lenses, binary or other diffractive optical lenses) can also
 be utilized.
 The present invention may also be used as a read only or a write once
 flying optical head, or alternatively as a flying optical head. Aspects of
 the present invention will be recognized by those skilled in the art as
 applicable to compact disks (CDs) and digital video disks (DVDs). Thus,
 those skilled in the art will also recognize that the present invention
 has aspects which are applicable to all optical storage systems.
 It should be understood that the geometry, compositions, and dimensions of
 the elements described herein may be modified within the scope of the
 invention and are not intended to be the exclusive; rather, they can be
 modified within the scope of the invention. Other modifications may be
 made when implementing the invention for a particular environment.