JP6455875B2 - Near-field optical device and magnetic head using the same - Google Patents

Description

  The present invention relates to the technical field of, for example, a near-field light device that provides a minute heat source using near-field light and a magnetic head including the near-field light device. The present invention is particularly suitable for heat assisted magnetic recording (HAMR).

  As a technique capable of further high-density magnetic recording, a heat-assisted magnetic recording (HAMR) method has attracted attention. This irradiates light to a near-field light generating part made of metal through an optical waveguide or the like, concentrates the light energy in a minute area, and raises the temperature of the minute area of the magnetic recording medium to perform magnetic recording. Technology.

  So far, various structures have been proposed in which the energy of light is concentrated in a minute region. For example, a configuration has been proposed in which a solid immersion lens is used to focus laser light on a near-field light generating unit made of so-called lollipop type gold (Au) or the like (see Patent Document 1). Alternatively, a configuration has been proposed in which a gold (Au) peg is arranged on the side surface of a disk-shaped ring resonator, the energy generated by the resonator is taken out by the peg, and the temperature of the minute region at the tip of the peg is raised. (See Patent Document 2). Or the structure which irradiates a semiconductor substrate containing a quantum dot with a laser beam and concentrates the energy of the incident light absorbed by this quantum dot to a metal edge is proposed (refer patent document 3). Alternatively, a configuration has been proposed in which a light emitting layer is sandwiched between a pair of electrodes, a protrusion is provided on one electrode, and energy from the light emitting layer is concentrated on the protrusion (see Patent Document 4).

US Patent No. 824889 US Patent Application Publication No. 2013/0286806 International Publication No. 2012/111816 JP 2014-53600 A

  In the near-field light generating unit for concentrating energy in the minute region as described above, there is a technical problem that the study from the viewpoint of controlling the generation of the near-field light has not been made.

  The present invention has been made in view of the above problems, for example, and uses a near-field light device (for example, NFT: Near Field Transducer) capable of efficiently generating near-field light and the near-field light device. An object is to provide a magnetic head.

In order to solve the above problems, a first near-field light device of the present invention includes an energy supplier that converts incident light energy into electromagnetic waves, and receives near-field light by receiving the electromagnetic wave energy from the energy adder. An energy injector for generating, wherein the energy charger and the energy injector are arranged at a distance of a near field distance that is a distance through which the energy of the electromagnetic wave can propagate, and the energy charger Has a ring shape .

  In order to solve the above problems, a first magnetic head of the present invention includes the near-field light device of the present invention, a light source that irradiates light to the near-field light device, and a write magnetic pole.

  In order to solve the above-described problem, a second magnetic head of the present invention includes a first near-field light device for raising a minute area of a magnetic recording medium to a first predetermined temperature, and the minute area, A second near-field light device for raising the temperature to a second predetermined temperature higher than the first predetermined temperature, wherein the first near-field light device and the second near-field light device are the present invention. This is a near-field optical device.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

It is a conceptual diagram which shows the outline | summary of the near field transducer which concerns on 1st Example. It is a conceptual diagram which shows the difference in the energy mode by the shape of an energy supplier. It is a conceptual diagram which shows the difference in the energy mode by the distance between an energy supplier and an energy injector. It is a conceptual diagram which shows the outline | summary of the near field transducer which concerns on 2nd Example. It is process drawing which shows a part of manufacturing process of the magnetic head based on an Example. FIG. 6 is a process diagram showing a process that follows the process of FIG. 5. It is process drawing which shows the process following the process of FIG. It is a figure which shows the example of a pattern drawn with an electron beam. It is a conceptual diagram which shows the 1st modification of the magnetic head based on an Example. It is a conceptual diagram which shows the 2nd modification of the magnetic head based on an Example. It is a conceptual diagram which shows the 3rd modification of the magnetic head based on an Example. It is a conceptual diagram which shows the 4th modification of the magnetic head based on an Example. It is a conceptual diagram which shows an example of the light emitting layer using a quantum dot. It is a conceptual diagram which shows the magnetic head which has a preheating function based on an Example. It is a conceptual diagram which shows the modification of the magnetic head which has a preheating function based on an Example. It is a conceptual diagram which shows the spectrometer which used the near field transducer.

  Embodiments according to the near-field light device and the magnetic head of the present invention will be described.

(Near-field optical device)
A first near-field light device according to an embodiment includes an energy adder that converts energy of incident light into electromagnetic waves, and an energy injector that receives the energy of electromagnetic waves from the energy adder and generates near-field light. Configured. Here, in particular, the energy supplier and the energy injector are arranged at a distance of the near field distance, which is the distance through which the electromagnetic wave energy can propagate.

  The near-field light device captures energy of incident light, that is, optical energy, and outputs at least a part of the captured energy as near-field light.

  Here, in order to efficiently supplement the optical energy, it is desirable that the shape of the energy supplier is not biased. For this reason, the energy supplier and the energy injector are not integrated but separated from each other. On the other hand, if the distance between the energy supplier and the energy injector is too large, energy is not efficiently transmitted from the energy supplier to the energy injector.

  Therefore, in the present embodiment, the energy supplier and the energy injector are arranged with an interval of the near field distance. Therefore, according to the first near-field light device according to the present embodiment, the energy of incident light can be efficiently converted into near-field light.

  In one aspect of the first near-field light device according to the embodiment, the energy charger is made of metal and has a disk shape or a ring shape, and the energy injector is made of metal and has a rod shape, The injector is arranged so that one end of the energy injector faces the side of the energy supplier.

  According to this aspect, the energy supplier is made of a metal such as gold (Au), silver (Ag), or aluminum. Similarly, the energy injector is made of metal. The metal constituting the energy supplier and the metal constituting the energy injector may be different from each other, but are preferably the same from the viewpoint of manufacturing the near-field light device.

  The energy supplier is disk-shaped or ring-shaped. On the other hand, the energy injector is rod-shaped. The energy supplier is typically larger than the energy injector. Moreover, the thickness (namely, the distance of a height direction) of an energy supply device may be larger than the thickness of an energy injector. However, from the viewpoint of manufacturing the near-field light device, it is desirable that the energy supplier and the energy injector have the same thickness.

  One end of the energy injector in the longitudinal direction is disposed so as to face the side of the energy supplier with a distance of the near field distance. That is, the near-field light device is a so-called lollipop type near-field light device.

  In this aspect, the near-field light device may constitute a part of the magnetic head, and the other end of the energy injector may be located at an ABS (Air Bearing Surface) of the magnetic head.

  With this configuration, it is possible to configure a magnetic head used for heat-assisted magnetic recording that can efficiently raise the temperature of the magnetic recording medium using optical energy, which is very advantageous in practice.

  The second near-field light device according to the embodiment includes an energy adder that converts energy of incident light into an electromagnetic wave, an energy injector that receives the energy of the electromagnetic wave from the energy adder and generates near-field light, It is configured with. Here, in particular, the energy supplier is ring-shaped and the energy injector is rod-shaped.

  According to the near-field light device, since the energy supply has a ring shape, the energy supply can efficiently convert the energy of incident light into an electromagnetic wave compared to a case where the energy supply has a disk shape, for example. it can. Therefore, according to the second near-field light device according to the present embodiment, the energy of incident light can be efficiently converted into near-field light. It should be noted that the energy supplier and the energy injector may be arranged at an interval of the above-mentioned near field distance.

(Magnetic head)
The first magnetic head according to the embodiment includes the first near-field light device according to the above-described embodiment, a light source that irradiates light to the near-field light device, and a writing magnetic pole.

  According to the first magnetic head, similarly to the first near-field light device according to the embodiment described above, the energy of incident light can be efficiently converted into near-field light. It should be noted that various known aspects can be applied to the light source and the writing magnetic pole, and thus the detailed description thereof is omitted.

  The second magnetic head according to the embodiment includes a first near-field light device for raising the temperature of a minute area of the magnetic recording medium to a first predetermined temperature, and a second area higher than the first predetermined temperature. And a second near-field light device for raising the temperature to a predetermined temperature. Here, in particular, the first near-field light device and the second near-field light device are the first near-field light devices according to the above-described embodiments.

  According to the second magnetic head, the energy of incident light can be efficiently converted into near-field light, as in the first near-field light device according to the embodiment described above. In particular, since the temperature of one minute region of the magnetic recording medium is raised in two steps using the first and second near-field light devices, respectively, the light incident on each of the first and second near-field light devices Can be reduced. That is, the output of the light source that irradiates light to the first and second near-field light devices can be suppressed.

  The second predetermined temperature is a temperature equal to or higher than the Curie temperature. The first predetermined temperature may be appropriately set according to the performance of each of the first and second near-field light devices.

  Embodiments according to the near-field light device of the present invention will be described with reference to the drawings. In the following embodiments, a near-field transducer (hereinafter referred to as “NFT” as appropriate) is taken as an example of the near-field light device of the present invention. Further, in each drawing referred to below, the scale is different for each layer and each member so that each layer and each member has a size that can be recognized on the drawing.

(Near field transducer)
<First embodiment>
A first embodiment of a near-field transducer will be described with reference to FIGS. FIG. 1A is a perspective view of the near-field transducer according to the first embodiment, and FIG. 1B is a plan view of the near-field transducer viewed from above.

  In FIG. 1, the NFT 10 includes an energy supplier 11 (sometimes referred to as a “disk”) and an energy injector 12 (sometimes referred to as a “peg” or “pin”). ing. The NFT 10 is referred to as a lollipop type NFT because of its external shape characteristics.

  The energy supplier 11 and the energy injector 12 are made of, for example, gold (Au). The energy feeder 11 has, for example, a disk shape with a diameter φ of 800 nm (nanometer) and a thickness of 20 nm. The energy injector 12 has, for example, a rod shape having a width w1 in the short direction of 100 nm, a width w2 in the longitudinal direction of 400 nm, and a thickness of 20 nm. The cross-sectional shape of the energy injector 12 is not limited to a circle but may be a polygon such as a square.

  Here, according to the inventor's research, the following matters have been found. That is, as the shape of the surface of the energy supplier 11 approaches a perfect circle, the energy mode becomes more stable (in other words, the amount of energy held in the energy supplier 11 increases or the energy loss decreases). For example, as shown in FIG. 2A, if the shape of the surface of the energy supplier is a perfect circle, the energy mode (shown conceptually by a shaded ellipse in the figure) is stable. On the other hand, as shown in FIG. 2B, when the shape of the surface of the energy supplier deviates from a perfect circle (that is, becomes an ellipse), the energy mode becomes unstable, and the amount of energy that can be held in the energy supplier 11 is increased. Get smaller.

  In addition, when the diameter φ of the energy supplier 11 and the frequency of light incident on the energy supplier 11 satisfy a predetermined relationship, the energy mode increases. The energy mode also increases when light having the resonance wavelength of the material constituting the energy supplier 11 enters the energy supplier 11 (light having a wavelength of 720 nm in the case of gold (Au)).

  For this reason, it is desirable that the shape of the surface of the energy supplier 11 is a perfect circle or a shape that can be regarded as a true circle in practice. In this case, since the incident light is not limited, the diameter φ of the energy supplier 11 may be appropriately set according to the specification of the product including the NFT 10 (the above-mentioned value “800 nm” is merely an example).

  As described above, when the shape of the surface of the energy supplier 11 deviates from a perfect circle, the energy mode becomes small. For this reason, as shown in FIG. 3A, when the energy injector is in contact with the energy supplier, the shape of the surface of the energy supplier deviates from a perfect circle, and the energy mode becomes smaller (that is, energy Loss increases).

  On the other hand, as shown in FIG. 3 (c), if the distance between the energy supplier and the energy injector is relatively large, energy is difficult to propagate from the energy supplier to the energy injector, and is generated in the energy injector. Near-field light is reduced (resulting in increased energy loss).

  In order to generate near-field light efficiently, it is necessary to appropriately set the distance between the energy supplier and the energy injector (see FIG. 3B). In this embodiment, the distance d is, for example, 50 nm.

  When the NFT 10 is used as a part of the magnetic head of the heat-assisted magnetic recording, in order to improve the energy conversion efficiency of the NFT 10, in addition to the above-described matters, the impedance between the NFT 10 and the magnetic recording medium is It is necessary to consider. That is, it is necessary to match the impedance between the energy feeder 11 and the energy injector 12 and the impedance between the energy injector 12 and the magnetic recording medium (that is, impedance matching needs to be performed).

  As an example of the impedance matching method, for example, the shape and size of each of the energy supplier 11 and the energy injector 12 and the change of the distance between the energy supplier 11 and the energy injector 12 can be cited.

<Second embodiment>
A second embodiment of the near field transducer will be described with reference to FIG. The second embodiment is the same as the first embodiment described above except that the shape of the energy charger is different. Therefore, in the second embodiment, the description overlapping with that of the first embodiment is omitted, and the common portions on the drawing are denoted by the same reference numerals, and only fundamentally different points are described with reference to FIG. explain. FIG. 4A is a perspective view of the near field transducer according to the second embodiment, and FIG. 4B is a plan view of the near field transducer as viewed from above.

  In FIG. 4, the NFT 20 includes an energy supplier 21 and an energy injector 12. Particularly in the present embodiment, the energy supplier 21 has a ring shape. If comprised in this way, the energy of incident light can be efficiently converted into electromagnetic waves rather than the disk-shaped energy feeder 11 which concerns on 1st Example.

  For example, the energy supplier 21 has an outer diameter φ1 of 800 nm, an inner diameter φ2 of 400 nm, and a thickness of 20 nm. The energy injector 22 has, for example, a width w1 in the short direction of 100 nm, a width w2 in the longitudinal direction of 400 nm, and a thickness of 20 nm.

(Method of manufacturing a magnetic head used for heat-assisted magnetic recording)
Next, an example of a method for manufacturing a magnetic head including the near-field transducer according to the first embodiment or the second embodiment and used for thermally assisted magnetic recording will be described with reference to FIGS.

In FIG. 5, a magnetic head layer (laminated body) 120 is laminated on a substrate 110 made of, for example, AlTiC (Al ₂ O ₃ —TiC). Note that various known objects can be applied to the method of forming the magnetic head layer 120, and therefore, detailed description thereof is omitted.

  Next, a separator 130 for bonding the magnetic head layer 120 and NFT is laminated on the magnetic head layer 120. The separator 130 is made of a magnetic material such as NiFe.

  Next, as shown in FIG. 6, a metal layer 140 made of a metal such as gold (Au) is laminated on the separator 130. Next, as shown in FIG. 7, a resist 150 is applied on the metal layer 140. Then, after a predetermined pattern is drawn using an electron beam, it is developed and the resist 150 is removed. As a result, on the separator 130, a metal pattern composed of NFT and a plurality of parts such as an etching stop portion is formed.

  Here, when the NFT 10 according to the first embodiment is formed, the pattern drawn by the electron beam is, for example, as shown in FIG. When the NFT 20 according to the second embodiment is formed, the pattern drawn by the electron beam is, for example, as shown in FIG.

  As a modification of the NFT 10, for example, as shown in FIG. 8B, a pattern having a slight protrusion on a portion facing the energy injector of the energy supplier may be drawn with an electron beam. Similarly, as a modification of the NFT 20, for example, as shown in FIG. 8D, a pattern having a slight protrusion on the portion facing the energy injector of the energy supplier may be drawn with an electron beam.

  That is, as long as the NFT can sufficiently supply the heat energy necessary for magnetic recording, the shape of the energy supplier may be slightly deviated from the perfect circle. Similarly, there is no problem even if the energy supplier and the energy injector are in contact.

  After the NFT is formed, an optical system (diffraction grating, optical waveguide, solid immersion mirror, etc.) for guiding laser light from an external laser light source, not shown here, to the NFT and condensing the laser light to the energy adder, etc. ) Is formed, and the tip of the magnetic head is completed.

(Modification)
Next, modified examples of the magnetic head including the NFT will be described with reference to FIGS. 9 to 11, the drawing of the magnetic head layer 120 and the like shown in FIGS. 5 to 7 is omitted.

<First Modification>
In the magnetic head described above, the NFT is formed on the separator 130. However, a semiconductor layer such as GaAs may be stacked on the separator 130, and the NFT may be formed on the semiconductor layer (see FIG. 9). In the configuration shown in FIG. 9, the semiconductor layer functions as an optically pumped semiconductor laser.

<Second Modification>
Alternatively, a metal layer as a lower electrode made of a metal such as gold (Au) is laminated on the separator 130, and a semiconductor layer such as GaAs is laminated on the metal layer. NFT may be formed on the substrate (see FIG. 10). In the configuration shown in FIG. 10, an NFT energy charger is also used as the upper electrode. The semiconductor layer functions as a semiconductor laser by applying a voltage between the lower electrode and the energy charger.

<Third Modification>
Alternatively, a VCSEL (Vertical Cavity Surface Emitting Laser) may be formed on the separator 130, a semiconductor layer such as GaAs may be stacked on the VCSEL, and an NFT may be formed on the semiconductor layer ( FIG. 11). In the configuration shown in FIG. 11, as in the configuration shown in FIG. 9, the semiconductor layer functions as an optically pumped semiconductor laser. By using the VCSEL, a waveguide is not necessary, and the entire magnetic head can be downsized.

<Fourth Modification>
Alternatively, as shown in FIG. 12, a metal layer 150 as a lower electrode made of a metal such as gold (Au) is laminated on the separator 130, and a plurality of quantum dots are included on the metal layer. A light emitting layer 160 to be stacked may be stacked, and a metal layer 140 to be NFT may be stacked on the light emitting layer 160.

  The light emitting layer 160 may be a multilayer quantum dot type in which, for example, 3 to 100 InAs quantum dot layers are stacked on a GaAs substrate as shown in FIG. As shown in b), a dispersed quantum dot type in which a plurality of InAs quantum dots are dispersed in a GaAs semiconductor layer may be used.

  If comprised in this way, the light emitting layer 160 functions as a quantum dot laser by applying a voltage between a lower electrode (namely, metal layer 150) and an energy supplier (namely, metal layer 140 after patterning). To do.

(Magnetic head with two NFTs)
Next, a magnetic head provided with two near-field transducers according to the first embodiment or the second embodiment and used for heat-assisted magnetic recording will be described with reference to FIGS.

  In FIG. 14, the magnetic head includes a write magnetic pole, a read magnetic pole, a first NFT, a second NFT, and a dielectric layer that joins the first NFT and the second NFT. It is configured. Here, the ends of the energy injectors of the first NFT and the second NFT on the side opposite to the side facing the energy supplier are located on the ABS of the magnetic head.

  In the magnetic head, near-field light converted from incident light is generated at the ends of the energy injectors of the first NFT and the second NFT. When recording information on the magnetic recording medium, first, the second NFT heats the minute region of the magnetic recording medium facing the energy injector of the second NFT to a first predetermined temperature that is a temperature lower than the Curie temperature. Is done. Subsequently, when the magnetic recording medium moves slightly along the traveling direction, the minute region is heated by the first NFT to a second predetermined temperature that is a temperature exceeding the Curie temperature. Thereafter, information is recorded in a minute region heated by the write magnetic pole.

  If comprised in this way, the intensity | strength of the light irradiated to 1st NFT and 2nd NFT can be suppressed, for example.

  In the magnetic head shown in FIG. 15, the first NFT and the second NFT are joined by a quantum dot semiconductor instead of the dielectric in the magnetic head shown in FIG. The quantum dot semiconductor functions as a quantum dot laser by using each of the first NFT and the second NFT as an electrode. With this configuration, the waveguide is not necessary, and the entire magnetic head can be downsized.

(Spectrograph using multiple NFTs)
A spectrometer having a plurality of near-field transducers according to the first embodiment or the second embodiment will be described with reference to FIG. FIG. 16 is a conceptual diagram showing a spectroscope using a near-field transducer.

  In FIG. 16, a spectroscope 510 includes a first NFT 511, a second NFT 512, and a third NFT 513 formed on a semiconductor substrate, an optical fiber 514 arranged to face the energy injector of the first NFT 511, The optical fiber 515 is disposed to face the energy injector of the second NFT 512, and the optical fiber 516 is disposed to face the energy injector of the third NFT 513.

For example, the outer diameter D1 and the inner diameter d1 of the energy adder are set so that the first NFT 511 emits light strongly with respect to the light with the wavelength λ1. NFT 511 becomes weaker or no longer emits light). For example, the outer diameter D2 and the inner diameter d2 of the energy supplier are set so that the second NFT 512 emits light strongly with respect to light having the wavelength λ2. For example, the outer diameter D3 and the inner diameter d3 of the energy adder are set so that the third NFT 513 emits light strongly with respect to light having the wavelength λ3.
Here, the wavelength relationship is λ1>λ2> λ3. The relationship between the outer diameters is D1>D2> D3. The relationship between the inner diameters is d1>d2> d3.

  When the incident light 500 is propagated through an optical fiber (not shown) or in the air and irradiated onto the spectroscope 510, the first NFT 511, the second NFT 512, and the third NFT 513 are respectively incident on the incident light 500. Illuminated.

  Here, when the incident light 500 is light of wavelength λ1, the first NFT 511 in the spectroscope 510 emits light (that is, the tip of the energy injector of the first NFT 511 emits strongly), and the optical fiber 514 is Then, the output light 520 is output to the outside of the spectroscope 510. Thereby, it is detected that the incident light 500 includes light of wavelength λ1. At this time, the second NFT 512 and the third NFT 513 do not react with the light having the wavelength λ1, and thus do not emit light (that is, the “output light 530” and “output light 540” in FIG. 16 do not occur).

  Further, when the incident light 500 does not include light of wavelength λ1, but includes light of wavelength λ2 and light of wavelength λ3, the second NFT 512 and the third NFT 513 in the spectrometer 510 emit light. At this time, light emitted from the second NFT 512 is output as output light 530 through the optical fiber 515, and light emitted from the third NFT 513 is output as output light 540 through the optical fiber 516. Thereby, it is detected that the incident light 500 includes light of wavelength λ2 and light of wavelength λ3. At this time, the first NFT 511 does not react to the incident light 500 and does not emit light.

  The spectroscope 510 shown in FIG. 16 is configured to split three different wavelengths. However, the number of wavelengths that can be detected is not limited to this. You can increase the number. Moreover, although it is set as the structure which takes out the output of 1st NFT511, 2nd NFT512, and 3rd NFT513 with the optical fibers 514-516, it may replace with the optical fibers 514-516 and may use a light receiving element. When the light receiving element is used, light emission of each of the first NFT 511, the second NFT 512, and the third NFT 513 is converted into an electric signal by the light receiving element and output to the outside.

  Further, it goes without saying that the NFT energy supplier used in the spectroscope 510 is not limited to the ring shape shown in FIG.

  In FIG. 16, the NFT is formed on the semiconductor substrate. However, the NFT may be formed on an image sensor having a predetermined number of pixels instead of the semiconductor substrate. By forming the NFT on the image sensor, it is possible to detect the light emission of the NFT at each pixel of the image sensor and acquire the light emission of the NFT as a two-dimensional image image. Furthermore, not only a lollipop type NFT composed of an energy injector and an energy supplier, but also a bar-shaped (bar-shaped) metal member may be formed as a set of vertical and horizontal on the image sensor. It is possible to detect the polarization component of the incident light by analyzing the two-dimensional image generated by detecting the output of the vertical bar and the light emission condition of the horizontal bar by the image sensor. is there.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and near-field light accompanying such a change. A device and a magnetic head using the device are also included in the technical scope of the present invention.

  10, 20 ... Near field transducer, 11, 21 ... Energy supply, 12, 22 ... Energy injector

Claims (5)

An energy supplier for converting the energy of incident light into electromagnetic waves;
An energy injector that receives the energy of the electromagnetic wave from the energy supplier and generates near-field light;
With
The energy feeder and the energy injector are arranged at a distance of a near field distance, which is a distance through which the energy of the electromagnetic wave can propagate ,
The near field light device according to claim 1, wherein the energy supplier has a ring shape . The energy supplier is made of metal ,
The energy injector is made of metal and has a rod shape,
The near-field light device according to claim 1, wherein the energy injector is disposed so that one end portion of the energy injector faces a side portion of the energy adder. The near-field light device constitutes a part of a magnetic head,
The near-field optical device according to claim 2, wherein the other end of the energy injector is located at an ABS of the magnetic head. The near-field light device according to claim 1 or 2,
A light source that emits light to the near-field light device;
Write pole,
A magnetic head comprising: A first near-field light device for raising a minute area of the magnetic recording medium to a first predetermined temperature;
A second near-field light device for raising the minute area to a second predetermined temperature higher than the first predetermined temperature;
With
The magnetic head according to claim 1, wherein the first near-field light device and the second near-field light device are the near-field light devices according to claim 1.