The present invention relates to a reader which uses a nano-spot of near-field light such as, for example, heat assisted magnetic recording (HAMR) and scanning near field optical microscope (SNOM), and a reproducing apparatus and a recording/reproducing apparatus which are provided with the reader.
As recording/reproducing technology which uses the near-field light, for example, there is proposed a recording apparatus in which a head unit is simplified by connecting a probe for generating the near-field light with a light emitting element and a light receiving element, as a unit, via an optical waveguide (refer to Patent document 1).
Moreover, thanks to recent advances in semiconductor microfabrication technology, nanoscale quantum dots have drawn attention, wherein the nanoscale quantum dots use ultimate particle properties by controlling a single electron with quantum mechanical effects. For example, following technologies are proposed: a production method for appropriately controlling the size of quantum dots (refer to Patent document 2), and a near-field concentrator using multi-layered quantum dots (refer to Patent document 3).
Patent document 1: Japanese Patent Application Laid Open No. 2007-317259
Patent document 2: Japanese Patent Application Laid Open No. 2009-231601
Patent document 3: Japanese Patent Application Laid Open No. 2006-080459
However, there is such a technical problem that the recording apparatus described in the aforementioned Patent document 1 has low energy utilization efficiency because of the use of the optical waveguide. It is also necessary to separately prepare a magnetic head in order to read magnetic information recorded on a recording medium.
In view of the aforementioned problem, it is therefore an object of the present invention to provide a reader which uses the near-field light, a reproducing apparatus, and a recording/reproducing apparatus which has high energy utilization efficiency.
The above object of the present invention can be solved by a reader is provided with a near-field light device having (i) one or a plurality of quantum dots and (ii) an output end laminated on an upper layer of the one or plurality of quantum dot layers, and a light receiving device which is configured to receive light caused by near-field light formed by the near-field light device upon reproduction of record information on a recording medium.
The above object of the present invention can be solved by a reproducing apparatus is provided with the reader of the present invention, a reproducing device which is configured to reproduce information on the basis of output from the light receiving device, and a controlling device which is configured to control the reader.
The above object of the present invention can be solved by a recording/reproducing apparatus is provided with the reader of the present invention, a reproducing device which is configured to reproduce information on the basis of output from the light receiving device, and a controlling device which is configured to control the reader.
The operation and other advantages of the present invention will become more apparent from an embodiment explained below.
Hereinafter, the embodiment of the recording/reproducing apparatus of the present invention will be explained with reference to the drawings. In each of the drawings below, each layer and each member have different scales so that each layer and each member have sizes large enough to be recognized on the drawing.
(Configuration of Recording/Reproducing Apparatus)
A configuration of the recording/reproducing apparatus in the embodiment will be explained with reference to
In
The head 12 is provided with a magnetic field generator 121, a near-field light device 122, an energy source 123, and a light receiver 124.
A specific structure of a main part of the head 12 will be explained with reference to
In
The near-field light device 122 is provided with a substrate 211 such as, for example, a GaAs substrate, a quantum dot layer 222 which is laminated on the substrate 211 and which contains, for example, indium arsenide (InAs) quantum dots, a quantum dot layer 223 which is laminated on the quantum dot layer 222 and which contains, for example, InAs quantum dots, and a metal end 224 which is laminated on the quantum dot layer 223.
The metal end 224 may not be made of one type of metal but may have a multilayer structure made of different metals. For example, the metal end 224 may have a two-layer structure in which a gold (Au) layer is formed on a chromium (Cr) layer, or a two-layer structure in which the gold (Au) layer is formed on a titanium (Ti) layer. Moreover, a thin film made of gold (Au) with a thickness of 20 nanometers (nm) to 100 nm may be further formed on the quantum dot layer 223, and the metal end 224 made of gold (Au) may be provided on the gold (Au) thin film. The metal film absorbs energy supplied from the quantum dot layers 222 and 223 which are below the metal film, and the absorbed energy is transferred to the metal end 224. This improves the utilization efficiency of incident energy.
The quantum dots contained in the quantum dot layer 222 receive light emitted from the energy source 123 and generate near-field light. The quantum dots contained in the quantum dot layer 223 receive the energy of the near-field light generated in the quantum dot layer 222 and generate near-field light. The quantum dots contained in the quantum dot layer 223 sometimes receive the light emitted from the energy source 123 and generate near-field light.
The metal end 224 can output to the exterior at least one portion of the energy of the near-field light generated in the quantum dot layer 223. Due to the multilayer quantum dot structure, it is possible to receive higher energy of incident light than a single-layer quantum dot layer and to focus the energy on the metal end 224, more efficiently. For example, the efficiency can be higher in order of three layers, five layers, and eight layers.
In the present invention, the energy of the incident light is transformed in the quantum dot layers 222 and 223, and the energy is focused on the metal end 224. This is different from such a phenomenon that the incident light is transmitted through InAs and GaAs and is directly applied to the metal end 224. By setting the size of the metal end 224 to be several tens nm or less (e.g. 20 nm or less), the energy of the incident light is transformed into the energy of the near-field light with the quantum dots, and the energy is focused on the metal end with a size of several tens nm or less. This is different from such a physical phenomenon that laser light is converged by an objective lens like an existing optical disc.
The light receiver 124 receives light caused by the near-field light formed by the near-field light device 122, or by the near-field light device 122 and a recording medium 50. The details will be described (later) with reference to
Here, the “light caused by the near-field light” means light which is not the near-field light such as, for example, scattered light generated by that the near-field light is scattered by some member (i.e. light in a far field).
Incidentally, various known aspects can be applied to the magnetic field generator 121, and thus, the explanation thereof will be omitted in order to avoid a complicated explanation.
Moreover, in order to protect the near-field light device 122, the magnetic field generator 121 and the light receiver 124 on the head 12, a side on which the near-field light device 121 is disposed may be covered with a dielectric substrate such as SiO2 and may be planarized so that the tip of the metal end 224 appears on a surface of the dielectric substance. By that the side is covered with the dielectric substance or the like, the members disposed on the head can be protected from an impact due to a contact with the recording medium.
Back in
The signal reader 16 is configured to generate a reproduction signal on the basis of the output of the light receiver 124. The rotation adjuster 17 is configured to adjust the number of rotations or a rotational speed of the recording medium 50. The CPU 11 integrally controls the position adjuster 13, the output adjusters 14 and 15, and the rotation adjuster 17.
The “CPU11”, the “head 12”, the “signal reader 16”, the “near-field light device 122”, the “light receiver 124” and the “metal end 224” in the embodiment are one example of the “controlling device”, the “reader”, the “reproducing device”, the “near-field light device”, the “light receiving device” and the “output end”, respectively.
(Recording Operation)
The operation of the recording/reproducing apparatus as configured above upon recording will be explained with reference to
The recording medium 50 is a magnetic recording medium and may be configured to contain metal such as, for example, gold (Au) in one portion of a layer structure of a magnetic substance or the like which easily interacts with the near-field light generated in the near-field light device 122.
If the energy source 123 is turned ON in accordance with a signal outputted from the output adjuster 15, near-field light is generated at least in a plurality of quantum dots in the quantum dot layers 222 and 223 contained in the near-field light device 122 due to the light (input energy) emitted from the energy source 123. The energy of the near-field light generated in a plurality of quantum dots in the quantum dot layer 222 is focused on the metal end 224 through a plurality of quantum dots in the quantum dot layer 223 to generate near-field light on the metal end 224. If the light emitted from the energy source 123 is applied to the plurality of quantum dots in the quantum dot layer 223, near-field light is generated by the plurality of quantum dots in the quantum dot layer 223, as in the plurality of quantum dots in the quantum dot layer 222. The energy of the near-field light generated by the quantum dots in the quantum dot layer 223 is focused on the metal end 224 to generate near-field light on the metal end 224. In other words, as illustrated in
If a distance between the metal end 224 and the recording medium 50 is greater than or equal to a predetermined distance (e.g. 20 nm), there is no interaction between the metal end 224 and the recording medium 50, and as illustrated in
On the other hand, if the distance between the metal end 224 and the recording medium 50 is less than the predetermined distance, as illustrated in
In this case, due to the heat caused by the energy of the near-field light, a heat spot having a higher temperature than the surroundings is formed, and coercive force of one portion of the recording medium 50 in the heat spot is reduced. The CPU 11 controls the magnetic field generator 121 (refer to
While keeping the situation in which the distance between the metal end 224 and the recording medium 50 is less than the predetermined distance, the CPU controls the energy source 123 via the output adjuster 15 and controls the magnetic field generator 121 via the output adjuster 14 on the basis of record information to be recorded. This makes it possible to continuously record the record information, for example, onto the recording medium 50 which rotates at a constant speed.
Moreover, the recording medium 50 can be not only a magnetic recording medium which uses the magnetic recording, but also a recording medium which uses a phase change material which causes a phase change, a material such as a coloring matter or pigment in which heat causes a chemical change, or various materials in which energy causes non-linear effect.
(Reproduction Operation)
The operation of the recording/reproducing apparatus upon reproduction will be explained with reference to
If the energy source 123 is turned ON in accordance with the signal outputted from the output adjuster 15 when the distance between the metal end 224 and the recording medium 50 is less than the predetermined distance, the energy of the incident light from the energy source 123 is transformed into near-field light in the quantum dot layers 222 and 223 and is transferred to the metal end 224 to generate near-field light on the metal end 224.
a) illustrates that there is no recording mark in the vicinity of the metal end 224 in the state in which the distance between the metal end 224 and the recording medium 50 is less than the predetermined distance.
When there is no recording mark (
The light receiver 124 receives the light caused by the near-field light which is generated on the metal end 224 or the quantum dots of the quantum dot layers 222 and 223 and which changes depending on the presence or absence of the recording mark, and outputs a signal corresponding to the received light. The signal reader 16 generates the reproduction signal on the basis of a signal outputted from the light receiver 124.
Here, according to the study of the present inventors, it is found that if the near-field light or the light caused by the near-field light is received, for example, the presence or absence of a recording mark or the like can be detected, and thus, the information recorded on the recording medium 50 can be read, because the state of the light caused by the near-field light (e.g. polarization, intensity, etc.) also changes.
Incidentally, in the near-field light device 122, as illustrated in
The light guide member 225 may be configured as a set of a plurality of small quantum dots, as illustrated in
Incidentally, the output of the energy source 123 may be set smaller upon reproduction than upon recording and may be controlled to an energy amount which does not rewrite the recording mark upon reproduction. Upon recording or upon reproduction, the output of the energy source 123 may be set always ON to keep the irradiation, and may be set as a pulse with a predetermined duty ratio.
Next, a first modified example of the near-field light device 122 will be explained with reference to
In
In order to receive the light caused by the near-field light generated in the near-field light device 122 configured as illustrated in
Alternatively, as illustrated in
Next, a second modified example of the near-field light device 122 will be explained with reference to
In
In the nano fountain layer 226, as illustrated in
By virtue of such a configuration, at least one portion of the energy of near-field light generated in the relatively small quantum dots which receive energy (i.e. input light) inputted from the back surface of the substrate 211 (the left side of
<Magnetic Recording>
Next, the magnetic recording which uses the head 12 will be explained with reference to
A representative example of the configuration of the magnetic recording is illustrated in
The writing of a recording signal onto the magnetic recording medium 50 is performed by modulation in a magnetic field direction of the near-field light device 122 and/or the magnetic field generator 121, due to an input signal (not illustrated). The writing can be performed not only by the modulation but also by ON/OFF of the magnetic field based on the input signal. The recording may be performed by a combination of the modulation and the ON/OFF of the magnetic field.
Moreover, in recording, the magnetic field is converged to the magnetic recording medium 50 and laser light enters the near-field light device 122 in response to the input signal, and then energy may be applied to a region on which the magnetic flux is focused by the near-field light which is generated in the near-field light device 122 and a partial region of the magnetic recording medium 50 (corresponding to the region on which magnetic flux is forced). Due to the near-field light, holding power of the magnetic recording layer 52 decreases in the region to which the energy is applied. This makes it easy to perform the magnetic recording.
The reading of the recording signal recorded on the magnetic recording medium 50 is performed by monitoring the intensity of the near-field light generated in the surroundings of the near-field light device 122 with the light receiver 124, or by detecting a change in current generated in the magnetic field generator 121 or the like due to the modulation of the magnetic field of the magnetic recording layer 52 according to a recording state (
The tip fine particle of the near-field light device 122 has not only the effect of energy propagation to a micro region of the magnetic recording medium 50 but also the effect of magnetic energy convergence to the micro region of the magnetic recording medium 50. By this, it is unnecessary to provide a reproduction-only magnetic head using TMG and GMR which is conventionally required, and it is possible to perform the extremely high-density writing/reading on the magnetic recording medium 50 by using only one device (the near-field light device 122).
Incidentally, the recording/reproducing apparatus 100 may be provided with a magnetic field reader and a signal reader which is configure to read an output signal of the magnetic field reader, in addition to the near-field light device 122.
The present invention is not limited to the aforementioned embodiments, but various changes may be made, if desired, without departing from the essence or spirit of the invention which can be read from the claims and the entire specification. A reader, and a reproducing apparatus and a recording/reproducing apparatus, which involve such changes, are also intended to be within the technical scope of the present invention.
Number | Date | Country | Kind |
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2011-209368 | Sep 2011 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2012/071592 | 8/27/2012 | WO | 00 | 3/21/2014 |