U.S. patent application number 13/403049 was filed with the patent office on 2013-08-29 for plasmonic funnel for focused optical delivery to a metallic medium.
This patent application is currently assigned to Seagate Technology LLC. The applicant listed for this patent is Kaizhong Gao, Amit Itagi, Michael Allen Seigler, Jie Zou. Invention is credited to Kaizhong Gao, Amit Itagi, Michael Allen Seigler, Jie Zou.
Application Number | 20130223196 13/403049 |
Document ID | / |
Family ID | 47912890 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130223196 |
Kind Code |
A1 |
Gao; Kaizhong ; et
al. |
August 29, 2013 |
PLASMONIC FUNNEL FOR FOCUSED OPTICAL DELIVERY TO A METALLIC
MEDIUM
Abstract
An apparatus includes a transducer including a plasmonic funnel
having first and second ends with the first end having a smaller
cross-sectional area than the second end, and a first section
positioned adjacent to the first end of the plasmonic funnel, and a
first waveguide having a core, positioned to cause light in the
core to excite surface plasmons on the transducer.
Inventors: |
Gao; Kaizhong; (Shoreview,
MN) ; Seigler; Michael Allen; (Pittsburgh, PA)
; Itagi; Amit; (Eden Prairie, MN) ; Zou; Jie;
(Eden Prairie, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gao; Kaizhong
Seigler; Michael Allen
Itagi; Amit
Zou; Jie |
Shoreview
Pittsburgh
Eden Prairie
Eden Prairie |
MN
PA
MN
MN |
US
US
US
US |
|
|
Assignee: |
Seagate Technology LLC
Cupertino
CA
|
Family ID: |
47912890 |
Appl. No.: |
13/403049 |
Filed: |
February 23, 2012 |
Current U.S.
Class: |
369/13.24 ;
250/492.1; G9B/11 |
Current CPC
Class: |
G02B 6/4291 20130101;
G02B 6/12002 20130101; G02B 6/1226 20130101; G11B 5/1278 20130101;
G11B 5/6088 20130101; G11B 2005/0021 20130101; G11B 5/4866
20130101; G02B 2006/121 20130101 |
Class at
Publication: |
369/13.24 ;
250/492.1; G9B/11 |
International
Class: |
G11B 11/00 20060101
G11B011/00; B01J 19/12 20060101 B01J019/12 |
Claims
1. An apparatus comprising: a transducer including a plasmonic
funnel including first and second ends with the first end having a
smaller cross-sectional area than the second end, and a first
section positioned adjacent to the first end of the plasmonic
funnel; and a first waveguide having a core, positioned to cause
light in the core to excite surface plasmons on the transducer.
2. The apparatus of claim 1, wherein a portion of the first
waveguide core is positioned adjacent to a side of the transducer
such that light in the waveguide core is evanescently coupled to
the transducer.
3. The apparatus of claim 1, wherein the transducer further
comprises: a second section positioned adjacent to the second end
of the plasmonic funnel.
4. The apparatus of claim 3, wherein an end of the first waveguide
core is positioned adjacent to an end the transducer such that
light in the waveguide core is end fire coupled to the
transducer.
5. The apparatus of claim 3, wherein the second section includes
first and second ends with the first end having a smaller
cross-sectional area than the second end, with the second end being
positioned adjacent to the second end of the plasmonic funnel.
6. The apparatus of claim 3, further comprising: a phase changing
element positioned along a side of the second section.
7. The apparatus of claim 6, wherein the phase changing element
comprises one of: a stub, an indent, or a protrusion.
8. The apparatus of claim 1, wherein the first waveguide comprises
one of: a channel waveguide, a solid immersion mirror, or a mode
index lens.
9. The apparatus of claim 8, further comprising: a polarization
rotator adjacent to the first waveguide.
10. The apparatus of claim 9, wherein the polarization rotator
comprises one of: first and second plasmonic stubs adjacent to
diagonally opposite edges of the dielectric channel waveguide.
11. The apparatus of claim 1, further comprising: a first magnetic
pole positioned adjacent to a side of the first section of the
transducer.
12. The apparatus of claim 11, further comprising: a second
magnetic pole; and a plasmonic shield positioned between the second
magnetic pole and the transducer.
13. The apparatus of claim 12, wherein a gap between the plasmonic
shield and the transducer is filled with dielectric material.
14. The apparatus of claim 1, further comprising: first and second
plasmonic shields positioned adjacent to opposite sides of the
first portion.
15. An apparatus comprising: a transducer including a plasmonic
funnel including first and second ends with the first end being
narrower than the second end, a first plasmonic waveguide
positioned adjacent to the first end of the plasmonic funnel, and a
second plasmonic waveguide positioned adjacent to the second end of
the plasmonic funnel; and a phase changing element positioned along
a side of the second plasmonic waveguide.
16. The apparatus of claim 15, wherein the phase changing element
comprises one of: a stub, an indent, or a protrusion.
17. An apparatus comprising: a recording medium; a recording head
having a transducer including a plasmonic funnel having first and
second ends with the first end having a smaller cross-sectional
area than the second end, and a first section positioned adjacent
to the first end of the plasmonic funnel, and a first waveguide
having a core, positioned to cause light in the core to excite
surface plasmons on the transducer; and a positioning means for
positioning the recording head adjacent to the storage medium.
18. The apparatus of claim 17, wherein a portion of the first
waveguide core is positioned adjacent to a side of the transducer
such that light in the waveguide core is evanescently coupled to
the transducer.
19. The apparatus of claim 17, wherein the transducer further
comprises: a second section positioned adjacent to the second end
of the plasmonic funnel.
20. The apparatus of claim 19, wherein an end of the first
waveguide core is positioned adjacent to an end the transducer such
that light in the waveguide core is end fire coupled to the
transducer.
Description
BACKGROUND
[0001] Heat assisted magnetic recording (HAMR) generally refers to
the concept of locally heating a recording medium to reduce the
coercivity of the medium so that an applied magnetic writing field
can more easily direct the magnetization of the medium during the
temporary magnetic softening of the medium caused by the heat
source. The heated area in the storage layer determines the data
bit dimension. A tightly confined, high power light spot is used to
heat a portion of the recording medium to substantially reduce the
coercivity of the heated portion. Then the heated portion is
subjected to a magnetic field that sets the direction of
magnetization of the heated portion. In this manner the coercivity
of the medium at ambient temperature can be much higher than the
coercivity during recording, thereby enabling stability of the
recorded bits at much higher storage densities and with much
smaller bit cells. Heat assisted magnetic recording is also
referred to a thermally assisted magnetic recording.
[0002] Near-field transducers can be used to focus light to a small
spot. An efficient means for concentrating light with a near-field
transducer would be beneficial in HAMR recording heads.
SUMMARY
[0003] In one aspect, the disclosure provides an apparatus
including a transducer including a plasmonic funnel having first
and second ends with the first end having a smaller cross-sectional
area than the second end, and a first section positioned adjacent
to the first end of the plasmonic funnel, and a first waveguide
having a core, positioned to cause light in the core to excite
surface plasmons on the transducer.
[0004] These and other features and advantages which characterize
the various embodiments of the present disclosure can be understood
in view of the following detailed description and the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic representation of portions of a
recording head including an embodiment.
[0006] FIG. 2 is a schematic representation of portions of another
recording head including an embodiment.
[0007] FIG. 3 is a cross-sectional view of FIG. 2 with an
additional magnetic pole.
[0008] FIGS. 4-8 are schematic cross-sectional views of several
examples of plasmonic funnels.
[0009] FIGS. 9 and 10 are schematic representations of a portion of
a dielectric channel waveguide and a mode converter in an
embodiment.
[0010] FIG. 11 is a schematic representation of portions of another
recording head including an embodiment.
[0011] FIG. 12 is a schematic representation of portions of another
recording head including an embodiment.
[0012] FIGS. 13-15 are schematic cross-sectional views of several
examples of plasmonic funnels.
[0013] FIG. 16 is a schematic representation of portions of another
recording head including an embodiment.
[0014] FIG. 17 is a schematic representation of portions of another
recording head including an embodiment.
[0015] FIG. 18 is a schematic representation of portions of another
recording head including an embodiment.
[0016] FIG. 19 is a graph of an electric field component of light
in the waveguide of FIG. 18.
[0017] FIG. 20 is a pictorial representation of a data storage
device in the form of a disc drive that can include a recording
head in accordance with an aspect of this disclosure.
DETAILED DESCRIPTION
[0018] In one aspect, this disclosure provides an apparatus for
focusing light to a small spot. In one embodiment, light is focused
from a first waveguide to a recording medium such that the focused
spot is much smaller than the diffraction limit.
[0019] FIG. 1 is a schematic representation of a portion of a
recording head 10 that may be used in a heat assisted magnetic
storage device. The recording head includes a first magnetic pole
12, which in this example is a write pole, a first waveguide in the
form of a dielectric channel waveguide 14 that includes a core
layer 16, and a tapered block plasmonic transducer 18 positioned
between a portion of the core layer of the waveguide and the pole.
The core is positioned to cause light in the core to excite surface
plasmons on the transducer. The core of the dielectric channel
waveguide has a substantially rectangular cross-sectional shape in
this example. The recording head is positioned adjacent to a data
storage medium 20, which can be a metallic medium. The recording
head may be separated from the storage medium by an air bearing
22.
[0020] In the example of FIG. 1, the plasmonic transducer includes
a first section 24 (also referred to as a plasmonic waveguide or
strip) having a substantially rectangular cross-sectional shape and
having substantially straight sides that lie in planes
substantially perpendicular to a plane of the storage medium; a
second section 26 (also referred to as a second plasmonic waveguide
or strip) having a substantially rectangular cross-sectional shape
and having substantially straight sides that lie in planes
substantially perpendicular to a plane of the storage medium; and a
plasmonic funnel section 28 positioned between the first and second
plasmonic waveguides. The plasmonic funnel section includes a first
(or bottom) end positioned adjacent to the first section, and a
second (or top) end positioned adjacent to the second section, with
the cross-sectional area of the first end being smaller than the
cross-sectional area of the second end.
[0021] The plasmonic funnel transducer serves as a near-field
transducer (NFT) and includes a tapered section that is tapered to
concentrate plasmons in a direction toward the first plasmonic
waveguide. In this example, the plasmonic funnel section includes
two substantially flat sides that are tilted to form edges that
meet edges of the sides of the first and second plasmonic
waveguides, and two other substantially flat sides that lie in
planes that are substantially perpendicular to the plane of the
storage medium and form edges that meet edges of the sides of the
first and second plasmonic waveguides. In FIG. 1 only one tilted
side 30 and only one flat side 32 of the tapered portion are
visible. An end 34 of the pole and an end 36 of the plasmonic
transducer are positioned adjacent to an air bearing surface 38 of
the recording head.
[0022] A portion 40 of the dielectric channel waveguide core is
positioned adjacent to a side 42 of the second plasmonic waveguide
such that light in the waveguide core is evanescently coupled to
the plasmonic transducer. A gap 44 can be provided between portion
40 and the side 42. The adjacent portions of the dielectric channel
waveguide core and the side of the second plasmonic waveguide form
a dielectric waveguide mode to plasmonic mode coupler. In
operation, light 46 from a light source such as a laser 48,
propagates through the dielectric channel waveguide and excites
local surface plasmons on the plasmonic transducer. Plasmons are
concentrated by the plasmonic funnel as they travel from the second
plasmonic waveguide (i.e., the second section of the transducer) to
the first plasmonic waveguide (i.e., the first section of the
transducer).
[0023] Light in the dielectric channel waveguide propagates through
the dielectric channel waveguide in an incident mode. The plasmonic
transducer 18 is positioned next to the core of the dielectric
channel waveguide. The tapered block plasmonic funnel and the first
and second plasmonic waveguides are made of a plasmonic material.
The plasmonic material can be, for example, gold, silver, copper,
aluminum, or alloys of these materials.
[0024] The magnetic write pole 12 is placed behind (or adjacent to)
the tapered block plasmonic transducer. The pole can be straight as
shown in FIG. 1, or in other embodiments, the pole can be sloped
toward the plasmonic funnel, or stacked. The region 49 surrounding
the transducer, waveguide core, and magnetic pole of FIG. 1 can be
filled with a dielectric material, that can serve as cladding
layers for the dielectric waveguide. The dielectric material can
be, for example, silica, silicon oxynitride, alumina, tantala,
magnesium oxide, silicon nitride, or titania. In the example of
FIG. 1, both the first and second plasmonic waveguides have a
rectangular cross-sectional shape in a plane substantially parallel
to the plane of the recording medium.
[0025] FIG. 2 is a schematic representation of portions of another
recording head 50, which includes many of the elements of the
recording head of FIG. 1, and further includes a plasmonic shield
52 that is positioned adjacent to a side of the first section of
the plasmonic funnel transducer opposite the first magnetic
pole.
[0026] FIG. 3 is a cross-sectional view of the recording head of
FIG. 2 showing a second magnetic pole 54. In this example, light
illustrated by a wavefront 56 travels through the dielectric
channel waveguide core in a transverse magnetic (TM) waveguide
mode, with an electric field oriented as shown by arrow 58. This
light excites surface plasmons 60 on the tapered block plasmonic
funnel transducer. The recording head is spaced from the data
storage medium by an air bearing 62. The plasmons are concentrated
by the plasmonic funnel into a small spot adjacent to an air
bearing surface 64 of the recording head.
[0027] The plasmonic front shield is shown to be positioned in
front of the plasmonic funnel transducer in FIG. 3. There is a
small gap 66 between the plasmonic funnel and the front shield. The
gap can be filled with dielectric materials of various refractive
indices. Such dielectric materials include, for example, silica,
silicon oxynitride, alumina, tantala, magnesium oxide, silicon
nitride, or titania. The material selection can be based on the
optical spot size created by the NFT, optical loss in the NFT,
and/or the efficiency of coupling to the media.
[0028] The magnetic writer has two poles. The first (or main) pole
12 is shown in FIG. 2. The second pole 54 can either be placed
behind the main pole, or in front of the plasmonic front shield,
and in contact with plasmonic front shield, as shown in FIG. 3. The
roles of the main pole and the second pole can be reversed in the
sense that either one can be made narrower than the other in the
cross-track direction (i.e., the Y-direction).
[0029] The plasmonic shield reduces the dissipation of the
plasmonic mode into the magnetic poles and reduces the optical spot
curvature in the medium. In addition, the front shield screens the
second pole from the plasmonic fields.
[0030] FIG. 3 can be used to explain the operation of the device.
Initially, light propagates in a TM mode in the dielectric channel
waveguide core. The electric field polarization direction is shown
in FIG. 3. The energy in this mode is transferred into a surface
plasmonic mode that runs along the face/edge 68 of the tapered
block plasmonic funnel transducer. As the mode propagates towards
the storage medium, the mode confinement becomes smaller and
smaller due to the taper in the plasmonic funnel. Finally, the
funnel ends in a narrow straight strip 36 (referred to as the first
section or the first plasmonic waveguide in FIG. 1). The strip can
be long enough (in a direction substantially perpendicular to the
storage medium) so that the fringing field at the junction between
the tapered funnel portion and the straight strip do not interact
with the medium. This ensures a low sensitivity to lapping during
fabrication of the recording head. Due to light delivery
constraints, it might be easier to launch a transverse electric
(TE) mode in the dielectric channel waveguide. In this case, the TE
mode can be converted to the surface plasmon mode on the edge of
the plasmonic funnel in the same manner as with the TM mode in FIG.
3, or the TE dielectric channel waveguide mode can be converted
into a TM dielectric channel waveguide mode as described below.
[0031] FIG. 4 shows the desired phase of the surface plasmon mode
on the plasmonic funnel, with plus and minus signs illustrating
relative phase. If a TE mode is converted to the surface plasmon
mode on the edge of the tapered block plasmonic funnel transducer,
the plasmon mode will have an opposite phase on either side of the
plasmonic funnel transducer, as illustrated in FIG. 5. This will
not produce a confined optical spot under the plasmonic funnel
transducer at the recording medium. To correct for this phase
difference, a 180.degree. phase shift can be introduced on one side
of the plasmonic funnel. This can be achieved by using a tuning
stub 70 as shown in FIG. 6, or by extending the path on one side to
obtain the desired optical path difference between the two sides.
The path can alternatively be extended by a groove 72 in one side
as shown in FIG. 7, or by a protrusion 74 on one side as shown in
FIG. 8.
[0032] In another example, the TE dielectric channel waveguide mode
can be converted into a TM dielectric channel waveguide mode using
a previously known technique in which two plasmonic studs of
appropriate length are placed diagonally with respect to the core
of the dielectric channel waveguide. A structure for implementing
this approach is shown in FIGS. 9 and 10, wherein FIG. 9 is a side
view and FIG. 10 is a cross-sectional view. Two plasmonic studs 80
and 82 are placed at diagonally opposite positions with respect to
the channel waveguide core. This introduces a cross-talk between
the TE and the TM modes. By choosing a suitable length of the
studs, the light that is launched as a TE mode can be converted to
a TM mode. The incident electric field component of the light is
shown as arrow 84 and the exiting electric field component of the
light is shown as arrow 86. Light travels in the direction of arrow
88.
[0033] Alternatively, the mode coupling method of surface plasmon
launching can be replaced with an end fire method. In the method
discussed above, the energy transfer takes place across a gap
between a portion of the core of the dielectric waveguide and the
plasmonic funnel transducer. Alternatively, these modes can be
launched using end-fire coupling. The end fire method can be
implemented using the structure shown in FIG. 11.
[0034] FIG. 11 shows a plasmonic funnel transducer 90 including a
first tapered section 92, a center section 94 having a
substantially rectangular cross-sectional shape, a second tapered
section 96 and a strip section 98 having a substantially
rectangular cross-sectional shape. A core layer 100 of a dielectric
channel waveguide 102 overlaps an end 104 of the plasmonic funnel
transducer in the downtrack direction (i.e., the X-direction). When
used in a recording head, the end 106 of the second rectangular
section would be positioned adjacent to an air bearing surface 108.
A small vertical gap 110 (normal to the air bearing surface of the
recording head) can be included between the plasmonic funnel and
the channel waveguide core. The funnel in FIG. 11 is tapered at the
top to provide for a gradual mode transfer from the dielectric
channel waveguide to the plasmonic funnel. With the top taper in
place, the small vertical gap 110 can be reduced to zero or be made
negative (i.e. the plasmonic funnel can be penetrated by the
waveguide core).
[0035] FIG. 12 is a schematic representation of portions of another
recording head 120. The recording head of FIG. 12 includes a
plasmonic funnel transducer 90 as shown in FIG. 11, in combination
with a channel waveguide core 122. The waveguide core is vertically
aligned with the plasmonic funnel transducer such that light
exiting the end 124 of the core is end fire coupled to the
plasmonic funnel transducer. The end of the core can be separated
from the plasmonic funnel transducer by a gap 126. Alternatively,
the end 124 can be in contact with the plasmonic funnel transducer
or embedded in it.
[0036] FIGS. 13-15 are schematic cross-sectional views of several
examples of plasmonic funnel transducers 130, 132 and 134.
Plasmonic funnel transducer 130 includes a first plasmonic
waveguide 136 and a second plasmonic waveguide 138. A tapered
section 140 is positioned between the first and second plasmonic
waveguides. The tapered section includes concave sides 142 and 144.
The first and second plasmonic waveguides, and the tapered section,
can have generally rectangular cross-sectional shapes in planes
perpendicular to the plane of the drawing. In various embodiments,
the tapered section can include two concave sides and two flat
sides, or four concave sides.
[0037] Plasmonic funnel transducer 132 includes a first plasmonic
waveguide 146 and a second plasmonic waveguide 148. A tapered
section 150 is positioned between the first and second plasmonic
waveguides. The tapered section includes convex sides 152 and 154.
The first and second plasmonic waveguides, and the tapered section,
can have generally rectangular cross-sectional shapes in planes
perpendicular to the plane of the drawing. In various embodiments,
the tapered section can include two convex sides and two flat
sides, or four convex sides.
[0038] Plasmonic funnel transducer 134 includes a first plasmonic
waveguide 156 and a second plasmonic waveguide 158. A tapered
section 160 is positioned between the first and second plasmonic
waveguides. The tapered section includes convex sides 162 and 164.
The first and second plasmonic waveguides, and the tapered section,
can have generally rectangular cross-sectional shapes in planes
perpendicular to the plane of the drawing. In various embodiments,
the tapered section can include two convex sides and two flat
sides, or four convex sides.
[0039] FIG. 16 is a schematic representation of portions of another
recording head 170. The recording head includes a first magnetic
pole 172, which in this example is a write pole and a plasmonic
funnel transducer 174 positioned adjacent to the pole. The
recording head is positioned adjacent to a data storage medium 176.
The recording head may be separated from the storage medium by an
air bearing 178.
[0040] In the example of FIG. 16, the plasmonic funnel transducer
includes a first plasmonic waveguide 180 having a substantially
rectangular cross-sectional shape and having substantially straight
sides that lie in planes substantially perpendicular to a plane of
the storage medium and a tapered funnel portion 182 positioned
above the first plasmonic waveguide. Plasmonic side shields 184 and
186 are positioned on opposite sides of the first plasmonic
waveguide and adjacent to the air bearing surface of the recording
head.
[0041] The plasmonic funnel is tapered to concentrate plasmons in a
direction toward the first plasmonic waveguide. In this example,
the plasmonic funnel includes two substantially flat sides that are
tilted to form edges that meet edges of the sides of the first
plasmonic waveguide, and two other substantially flat sides that
lie in planes that are substantially perpendicular to the plane of
the storage medium and form edges that meet edges of the sides of
the first plasmonic waveguides. In FIG. 16 only one tilted side 188
and only one flat side 190 of the tapered portion are visible. An
end 192 of the pole and an end 194 of the plasmonic transducer are
positioned adjacent to an air bearing surface 196 of the recording
head. In another embodiment, the side shields can be used in
combination with a front shield as shown in FIG. 2.
[0042] FIG. 17 is a schematic representation of portions of another
recording head 200. The recording head of FIG. 17 includes a planar
waveguide 202 in the form of solid immersion mirror (SIM) having a
core layer 204. The sides 206 and 208 of the solid immersion mirror
are shaped to direct light in the core to a focal point 210. The
core layer is positioned such that light exiting the core layer
excites surface plasmons on the plasmonic funnel transducer 90. The
SIM core layer can be vertically aligned with the plasmonic funnel
transducer for end fire coupling, or the core can be offset from
the plane of the plasmonic funnel transducer for evanescent
coupling.
[0043] FIG. 18 is a schematic representation of portions of another
recording head 220. The recording head of FIG. 18 includes a
waveguide 222 in the form of mode index lens 224 having a core
layer 226 with a first region 228 and a second region 230 having a
thickness larger than the thickness of the first region. The edge
of the second region is shaped to direct light in the core to a
focal point 230. The mode index lens is positioned such that light
exiting the core layer excites surface plasmons on the plasmonic
funnel transducer 90. The mode index lens can be vertically aligned
with the plasmonic funnel transducer for end fire coupling, or it
can be offset from the plane of the plasmonic funnel transducer for
evanescent coupling.
[0044] FIG. 19 is a graph of an electric field component of light
in the waveguide of FIG. 18. To obtain the desired phase of light
exiting the mode index lens, the electric field component of light
region 228 can be asymmetric with respect to the center of the mode
index lens in a plane perpendicular to the plane of the drawing.
The desired electric field is shown in the region between the
arrows 232 and 234 in FIG. 19. If the desired phase is not obtained
in this manner, the tuning stubs shown in FIGS. 9 and 10 could be
used to obtain the desired phase.
[0045] In FIGS. 1-18, only selected components of the apparatus are
shown. It will be apparent to those skilled in the art that other
components can be included in a practical device. For example, the
components in FIGS. 1-18 can be embedded in or surrounded by
material, which may be dielectric material, that supports the
illustrated components and maintains the relative position of the
illustrated components.
[0046] FIG. 20 is a pictorial representation of a magnetic storage
device in the form of a disc drive that can include a recording
head constructed in accordance with the disclosure. The disc drive
240 includes a housing 242 (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 240
includes a spindle motor 244 for rotating at least one storage
medium 246, which may be a magnetic recording medium, within the
housing 242. At least one arm or other positioning device 248 is
contained within the housing 242, with each arm 248 having a first
end 250 with a recording head or slider 252, and a second end 254
pivotally mounted on a shaft by a bearing 256. An actuator motor
258 is located at the arm's second end 254 for pivoting the arm 248
to position the recording head 252 over a desired sector or track
260 of the disc 246. The actuator motor 258 is regulated by a
controller, which is not shown in this view and is well-known in
the art.
[0047] For heat assisted magnetic recording (HAMR), 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. The
recording head can include a laser, channel waveguide, and
plasmonic funnel transducer as shown in FIGS. 1-18 on a slider to
guide light to the storage medium for localized heating of the
storage medium.
[0048] The various examples described above include a dielectric
waveguide mode to plasmonic mode coupler, a plasmonic funnel
transducer, and a narrow plasmonic waveguide or strip positioned
adjacent to a tapered section. An optional polarization rotator can
also be included. The apparatus can be used for light delivery in
heat assisted magnetic recording. It can also be used in other
applications that require coupling between two waveguides.
[0049] In one aspect, the disclosure provides a transducer
including a plasmonic funnel including first and second ends with
the first end being narrower than the second end, a first plasmonic
waveguide positioned adjacent to the first end of the plasmonic
funnel, and a second plasmonic waveguide positioned adjacent to the
second end of the plasmonic funnel, wherein a phase changing
element is positioned along a side of the second plasmonic
waveguide. The phase changing element can be, for example, a stub,
an indent, or a protrusion.
[0050] In another aspect, the disclosure provides an apparatus
including a recording medium; a recording head having a transducer
including a plasmonic funnel having first and second ends with the
first end having a smaller cross-sectional area than the second
end, and a first section positioned adjacent to the first end of
the plasmonic funnel, and a first waveguide having a core, with a
portion of the core positioned to cause light in the core to excite
surface plasmons on the transducer; and a positioning means for
positioning the recording head adjacent to the storage medium. A
portion of the first waveguide core can be positioned adjacent to a
side of the transducer such that light in the waveguide core is
evanescently coupled to the transducer. The transducer can also
include a second section positioned adjacent to the second end of
the plasmonic funnel. An end of the first waveguide core can be
positioned adjacent to an end the transducer such that light in the
waveguide core is end fire coupled to the transducer.
[0051] It is to be understood that even though numerous
characteristics and advantages of various embodiments of the
present invention have been set forth in the foregoing description,
together with details of the structure and function of various
embodiments of the invention, this detailed description is
illustrative only, and changes may be made in detail, especially in
matters of structure and arrangements of parts within the
principles of the present invention to the full extent indicated by
the broad general meaning of the terms in which the appended claims
are expressed. For example, the particular elements may vary
depending on the particular application without departing from the
spirit and scope of the present invention.
* * * * *