JP4567071B2 - Optical head and information storage device - Google Patents

Description

  The present invention relates to an optical head and an information storage device using the optical head.

  With the progress of the information society, the amount of information continues to increase. In response to this increase in the amount of information, an information recording method with a remarkably high recording density and a recording / reproducing apparatus based thereon are desired. In an optical disc apparatus which is a kind of information recording / reproducing apparatus, the diameter of the focused beam related to the recording capacity is limited by the light wavelength. Measures for increasing the recording density of optical disk devices include shortening the wavelength of the laser used and increasing the numerical aperture (NA) of the optical lens, but there is a limit to increasing the recording density due to the diffraction limit.

  As a measure to increase the NA of optical lenses, a solid immersion lens is used, the numerical aperture (NA) is set to 1 or more, and the evanescent light that oozes from the bottom surface of the solid immersion lens is used to store information on the optical disk medium. A method of recording is proposed. However, in this method, since the NA is improved by the refractive index of the solid immersion lens, there is a limit to increase the recording density.

  As a recording method for realizing a high recording density, a near-field is created in which a small aperture smaller than the wavelength of incident light is created and a beam spot smaller than the wavelength of light is formed using near-field light generated from the aperture. Optical recording systems are attracting attention.

  As a structure for generating near-field light (near-field optical probe), a sharpened optical fiber (optical fiber probe) having a minute aperture equal to or smaller than the light wavelength is widely used. This optical fiber probe is manufactured by stretching one end of the optical fiber while heating it or sharpening it by using a chemical etching method and then coating the other end with a metal.

  When light is introduced into the optical fiber, near-field light can be generated in the vicinity of the minute opening formed at the tip of the optical fiber. However, this optical fiber probe has a drawback that the light utilization efficiency is low. For example, when the aperture diameter is 100 nm, the ratio between the intensity of light incident on the optical fiber and the intensity of light emitted from the tip of the optical fiber is 0.001% or less.

  The following probes have been proposed as methods for improving light utilization efficiency.

(1) Multi-step sharpened fiber probe An optical fiber probe that changes the sharpness of the tip of the optical fiber in two steps or three steps from the root to the tip (Applied Physics Letters, Vol. 68, No. 19, p2612-2614 1996; Applied Physics Letters, Vol. 73, No. 15, p2090-2092, 1998).

(2) Metal Needle Probe A needle of a scanning tunnel microscope (STM) is used as a probe, and a strong near-field light is generated in the vicinity of the tip by irradiating the tip of the needle (Japanese Patent Laid-Open No. 6-137847). Publication).

(3) Micro-aperture fiber probe with metal microspheres This is a fiber probe in which a metal microsphere is formed at the center of the microaperture at the tip of the optical fiber, and plasmons are excited in the metal microsphere by the light emitted from the microaperture. Strong near-field light is generated in the vicinity of the metal sphere (Japanese Patent Laid-Open No. 11-101809).

(4) Metal-coated glass piece probe A metal film having a thickness of about 50 nm is formed on a glass piece cut into a triangular prism shape, and surface plasmons are excited on the metal film. Surface plasmons propagate toward the apex, and strong near-field light is generated near the apex (Physical Review B, Vol. 55, No. 12, p7977-7984, 1997).

(5) Glass substrate probe with a metal scatterer A probe having a metal scatterer attached to the bottom of a glass substrate, and strong near-field light is generated in the vicinity of the metal scatterer (Japanese Patent Laid-Open No. 11-250460).

  By the way, in the near-field optical system, the distance between the microstructure that generates near-field light and the sample surface needs to be several nm to several tens nm. Therefore, when using a probe made of the above optical fiber or glass piece, a special control system for controlling the distance between the probe tip and the sample surface is required.

  In general, the distance is measured using an atomic force acting between the probe tip and the sample, and servo control is performed using the measured value. However, when this servo control is used, there is a limit to the scanning speed of the probe because the servo band is limited.

  In particular, in an optical recording / reproducing apparatus that requires a high data transfer speed, it is necessary to scan the probe at a high speed on the optical disk, and the above-mentioned servo control method can control high frequency interval fluctuations caused by distortion and tilt of the optical disk. There is a problem that it cannot be done.

  In order to solve this problem, the following probes have been proposed.

(1) Planar aperture probe A probe in which an opening is formed in a silicon substrate using anisotropic etching, and the periphery of the micro aperture is flat, so that the interval is kept constant by pressing the probe against the sample. (The Pacific Rim Conference on Lasers and Electro-Optics, WL2,199).

(2) Opening probe with pad A probe having a square pyramid protrusion with a small opening at the tip on the bottom surface of the glass substrate and a pad formed around the protrusion. The pad keeps the distance between the probe tip and the sample constant. (Japanese Patent Laid-Open No. 11-265520).

(3) Surface emitting laser probe with a metal microchip A probe having a metal aperture and a metal projection formed on the end surface of a surface emitting laser. The structure is flat. By pressing the probe against the sample The interval can be kept constant (Applied Physics Vol. 68, No. 12, p1380-1383, 1999). Since it has a metal microprotrusion and a resonance structure, the light utilization efficiency can be improved.

  (4) Applying patch antennas and coaxial cables to light to generate near-field light with high efficiency (Optics Communications Vol. 69, No. 3, 4, p219-224, 1989).

  (5) By using a bow-tie metal piece as a minute dipole antenna, minute near-field light is generated with high efficiency (US Pat. No. 5,696,372).

  By the way, the following three points are required as the performance of the optical memory using near-field light.

  (A) The distance between the near-field light and the recording medium is strictly controlled on the order much smaller than the wavelength.

  (B) It should be a minute beam spot.

  (C) High light utilization efficiency, that is, high-speed data transfer is possible.

  A fiber probe with a sharp tip angle changed in multiple stages has an efficiency 10 to 100 times higher than that of a generally used fiber probe, but is an optical recording / reproducing apparatus that requires a light utilization efficiency of 0.5% or more. It is still insufficient for application. Further, since an optical fiber is used, it is mechanically fragile and high-speed scanning is impossible.

  Metal needle probe, micro-aperture fiber probe with metal microsphere, metal-coated glass piece probe, and glass substrate probe with metal scatterer all improve the efficiency by utilizing the characteristics of metal, and high light utilization efficiency Can be expected.

  However, in either case, the probe tip is mechanically fragile and is not suitable for high-speed scanning. In particular, a metal needle probe or a glass substrate probe with a metal scatterer has a disadvantage that a lot of background light is detected because light that does not strike the needle tip or scatterer also enters the sample.

  Several probes capable of high-speed scanning have been proposed as described above. However, in the case of a planar aperture probe and an aperture probe with a pad, high-speed scanning is possible but light utilization efficiency is small. For a minute aperture, a FDTD method (Finite Difference Time) is used in a model in which a substrate with a thickness of 560 nm made of aluminum is provided with a taper angle of 30 °, a minute aperture is 100 nm in diameter, and light having a wavelength of 400 nm is incident. Strict electromagnetic field calculations were performed using the domain method.

  As a result, as shown in FIG. 1, when a beam is incident on a metal micro-aperture having a diameter of 100 nm, the beam is 160 nm (full width at half maximum) exceeding the aperture size even in the near-field region immediately after emission, and is particularly angular in the incident polarization direction. Therefore, high density recording is difficult.

  The surface emitting laser probe with metal microprotrusions is expected to have high light scanning efficiency, high light utilization efficiency, and low background light. However, in order to generate strong near-field light using the metal microprotrusions, it is necessary to optimize the shape of the metal, but there is no disclosure in JP-A-11-101809 regarding the shape. Also, there is no disclosure regarding the manufacturing method.

  In the method of generating near-field light with high efficiency by applying a patch antenna and coaxial cable to light, or the method of generating minute near-field light by using a bow-tie metal piece as a minute dipole antenna, the freedom of metal Light intensity is amplified using plasmon resonance conditions by electrons. As a result of rigorous electromagnetic calculation by the FDTD method as described above, recording is performed within a distance of 2 to 3 nm from the bow tie antenna surface as shown in FIG. As long as no surface is placed, the effect is the same as a perfect conductor without plasmon enhancement.

  That is, there is a problem that the intensity is not increased and the required light quantity of 0.5% or more cannot be obtained. In addition, there is a problem that a tolerance value such as a bow-tie shape that satisfies the plasmon condition is small.

  On the other hand, a method of increasing the recording density by attaching a lens-shaped substrate in an optical disk medium has been announced (Optical Data Storage 2001 Technical Digest pp277-279, Guerra, et. Al, April 22-25, 2001).

  The purpose of this method is to solve problems such as dust and head disk interface, but instead of using near-field light, information is recorded on the recording film using light collected by the microlens and built in the microlens. Is recorded and reproduced. Although the recording density is increased by increasing the refractive index of the lens material, there are problems in that there is a limit to increasing the refractive index and the recording density in the circumferential direction cannot be improved.

  Accordingly, an object of the present invention is to provide an optical head using near-field light that has high light utilization efficiency and can be scanned at high speed.

  Another object of the present invention is to provide an information recording / reproducing apparatus capable of high-density recording using the optical head described above.

According to an aspect of the present invention, a first dielectric having a first refractive index that serves as a light transmission portion, and a first dielectric larger than the first refractive index, disposed adjacent to both sides of the first dielectric. A pair of second dielectrics having a refractive index of 2, a pair of third dielectrics disposed adjacent to the second dielectrics, and disposed adjacent to the third dielectrics, A pair of fourth dielectrics having a third refractive index greater than the first refractive index, and a combined width of the two layers of the first dielectric and the second dielectric and the third dielectric; The combined width of the two layers of the fourth dielectric is less than or equal to the wavelength of incident light, and the combined width of the two layers of the first dielectric and the second dielectric is the third dielectric and the first dielectric. 4 rather smaller than the width of a combination of two layers of dielectric, the third dielectric and the fourth dielectric not output the transmitted light of the incident light On the first dielectric optical head and outputs the transmitted light of the incident light.

  Preferably, the first and third dielectrics have different refractive indexes. More preferably, the third dielectric has a fourth refractive index smaller than the first refractive index. As an alternative, the first and third dielectrics have different thicknesses.

  Preferably, the third dielectric has a greater thickness than the first dielectric. Preferably, the light incident on the optical head is linearly polarized light having a polarization plane in a direction orthogonal to the stacking direction of the dielectrics.

According to another aspect of the present invention, a first dielectric serving as a light transmission portion, a pair of first adjacent materials having a negative dielectric constant, disposed adjacent to both sides of the first dielectric, A pair of second dielectrics disposed adjacent to each first adjacent material; and a pair of second adjacent materials having a negative dielectric constant disposed adjacent to each second dielectric. The first and second dielectrics have different refractive indexes or different thicknesses, and a combined width of the first dielectric and the two layers of the first adjacent material and the second dielectric The combined width of the two layers of the second adjacent material is less than or equal to the wavelength of incident light, and the combined width of the first dielectric and the two layers of the first adjacent material is the second dielectric and the second 2 rather smaller than the width of a combination of two layers of adjacent material, the second dielectric and said second adjacent material exits the transmitted light of the incident light And the first dielectric outputs the transmitted light of the incident light, and the real part absolute value of the dielectric constant of the first adjacent material is larger than the dielectric constant of the first and second dielectrics, There is provided an optical head characterized in that the real part absolute value of the dielectric constant of the second adjacent material is larger than the dielectric constant of the second dielectric .

  Preferably, the first dielectric has a first refractive index, and each second dielectric has a second refractive index greater than the first refractive index. As an alternative, the first dielectric has a first thickness and each second dielectric has a second thickness that is greater than the first thickness. Preferably, the light incident on the optical head is linearly polarized light having a polarization plane in a direction orthogonal to the stacking direction of each dielectric and adjacent material.

  According to still another aspect of the present invention, incident light is incident from a direction perpendicular to the stacking direction of each dielectric or dielectric / adjacent material, and from linearly polarized light having a polarization plane in the direction orthogonal to the stacking direction. Composed.

  Preferably, the optical head is a cylindrical optical head, and the second to fourth dielectrics or the first and second adjacent materials and the second dielectric have a ring shape.

According to still another aspect of the present invention, an information storage device that records or reproduces information on a recording medium, a light source that emits a light beam, and an optical head that irradiates the recording medium with light based on the light beam; And the optical head is a light transmission part, and has a first dielectric having a first refractive index, and is disposed adjacent to both sides of the first dielectric, and is larger than the first refractive index. A pair of second dielectrics having a second refractive index, a pair of third dielectrics disposed adjacent to each of the second dielectrics, and disposed adjacent to each of the third dielectrics; A pair of fourth dielectrics having a third refractive index greater than the first refractive index, and a combined width of the two layers of the first dielectric and the second dielectric and the third dielectric And the two layers of the fourth dielectric are less than the wavelength of the incident light, and the first Collector and the width of a combination of two layers of the second dielectric is minor than the width of a combination of two layers of the said third dielectric fourth dielectric, the third dielectric and the fourth dielectric An information storage device is provided in which the first dielectric outputs the transmitted light of the incident light without outputting the transmitted light of the incident light .

According to still another aspect of the present invention, an information storage device that records or reproduces information on a recording medium, a light source that emits a light beam, and an optical head that irradiates the recording medium with light based on the light beam; The optical head includes: a first dielectric serving as a light transmission portion; a pair of first adjacent materials having a negative dielectric constant, disposed adjacent to both sides of the first dielectric; A pair of second dielectrics disposed adjacent to each first adjacent material; and a pair of second adjacent materials having a negative dielectric constant disposed adjacent to each second dielectric. The first and second dielectrics have different refractive indexes or different thicknesses, and a combined width of the first dielectric and the two layers of the first adjacent material and the second dielectric The combined width of the two layers of the second adjacent material is equal to or less than the wavelength of incident light, and the first Collector and the width of a combination of two layers of the first adjacent member is minor than the width of a combination of two layers of the said second dielectric second adjacent member, said second dielectric and said second adjacent material The first dielectric outputs the incident light transmitted without outputting the transmitted light of the incident light, and the real part absolute value of the dielectric constant of the first adjacent material is the first and second dielectrics. There is provided an information storage device characterized in that the absolute value of the real part of the dielectric constant of the second adjacent material is larger than the dielectric constant of the second dielectric .

  In order to generate minute light, it is conceivable to use a minute opening in two dimensions and a single slit in one dimension, but an opening or slit having a size smaller than the wavelength of light (for example, about 100 nm in length) ), The transmitted light is extremely weak. In view of such circumstances, the present inventors paid attention to a diffraction grating formed periodically.

  When the difference between the refractive index of the high refractive index and the low refractive index is very large, it may show a peculiar behavior with respect to light transmission, etc., but the behavior of light in such a situation has been studied in detail so far. There wasn't. As such a high refractive index material, attention is paid to the use of a wide gap semiconductor such as III-V.

  Usually, in the case of a transmission type diffraction grating, when the length (pitch) of the period of the diffraction grating is larger than the wavelength of incident light, all the light beams incident on the plurality of diffraction gratings are transmitted or diffracted. For this reason, the transmitted light, which is a light beam, inevitably becomes a beam having many peaks and valleys in the near field, and the beam becomes greatly blurred in the far field.

  For this reason, in order to obtain a fine light beam below the diffraction limit, the entire surface of the diffraction grating is covered with a metal or the like, and a fine aperture of, for example, about 200 nm below the light wavelength and below the diffraction limit used in one place. There has been proposed a method of making a space with a focus ion beam. Thus, the plasmon excitation light by the metal diffraction grating is emitted from the minute aperture.

  However, in this method, the efficiency of using the light emitted from the aperture is low, the processing of the focus ion beam is not suitable for mass production, and the size and shape of the processing of the aperture by the focus ion beam is small. There is a problem of being unstable. Further, there is a problem that this method is not suitable for manufacturing an optical device intended to be manufactured with a wafer in order to mass-produce at low cost.

  The present invention has an advantage that a beam much smaller than the diffraction limit can be generated with high efficiency without creating an aperture by focus ion beam processing or the like. We have an optical element with a special periodic structure that has a very small number of periods and the components forming the period are not the same. It was found by calculation for the first time that it can be transmitted.

  First, a method of using the difference in refractive index between a medium having a high refractive index and a medium having a low refractive index in order to confine light will be described. In the following description, a laser used for optical recording and reproduction is a blue-violet laser diode (wavelength 400 nm).

  Here, the high refractive index material is silicon (Si), and the refractive index of Si at a wavelength of 400 nm is 5.56. On the other hand, the material having a low refractive index is diamond, and the refractive index of diamond at a wavelength of 400 nm is 2.47. The refractive index difference is as large as 3.1, and the behavior of light at this time causes a unique phenomenon called anomalous diffraction as will be described later.

  When the periodic length (pitch) d of the diffraction grating is less than or equal to the wavelength λ (not including 0), diffracted light is not generated. Even shorter periods may make it difficult to produce diffraction gratings, and have not been studied in detail.

  However, the present inventors have found by calculation that the transmitted light comes out without attenuation when the period length d is made finer, for example, λ / 5 or less (not including 0). In other words, a diffraction grating with a certain refractive index and a higher refractive index is formed, and when the period length of the diffraction grating falls below a certain period length, which is less than the wavelength used, an abnormal diffraction phenomenon in which transmitted light strongly appears is calculated. It was found by.

  On the other hand, when the period length of the diffraction grating is equal to or greater than a certain period length which is less than or equal to the wavelength used, it has been found by calculation that almost no transmitted light is emitted.

  From these phenomena, a combination of the center is divided into a first dielectric having a first refractive index disposed in the center, and a higher refractive index than the first refractive index disposed adjacent to both sides of the first dielectric. And a second dielectric having a width equal to or less than a certain period length (not including 0).

  Both sides of the center combination are formed with a combination of a third dielectric having a second refractive index and a fourth dielectric having a refractive index higher than the second refractive index, with a width of a certain period length or more. To do.

  By forming in this way, the transmitted light from the adjacent portion of the central combination is not generated, the light is confined in the central dielectric combination, and is strongly emitted and attenuated as the transmitted light that is the 0th-order diffracted light. It propagates in the diffraction grating without any problem. The present invention is characterized in that such light confinement can be achieved even with only about three periods without having many periods.

  In the following calculation of light, exact electromagnetic field calculation was performed by the FDTD method. In addition, 120 cells in the X and Z directions were 10 nm each, 240 cells in the Y direction were 5 nm each, and the calculation was performed using the result of 30 cycles that reached a steady state.

  In addition, in order to stabilize the calculation solution even for a metal that is a negative dielectric, an accurate solution can be obtained by simultaneously calculating the free electron motion equation by Lorentz, which is a metal free electron model, simultaneously with the FDTD method. It has come to be obtained.

  Referring to FIG. 3, a schematic perspective view of the optical head 2 according to the first embodiment of the present invention is shown. In this embodiment, the trapezoidal column 4 includes a pair of trapezoidal main surfaces 4a parallel to each other, a rectangular bottom surface 4b, a rectangular top surface 4c parallel to the rectangular bottom surface 4b, a top surface 4c and a bottom surface 4b, and a pair. The trapezoidal main surfaces 4a have a pair of inclined side surfaces 4d. The trapezoidal column 4 is made of a transparent diamond with respect to the light having a refractive index of 2.47.

  In the trapezoidal column optical head, blue-violet light having linearly polarized light in the X direction is incident on the rectangular bottom surface 4b, and the light is multiply reflected by the side surface 4d of the trapezoidal column 4 to interfere with each other. Although it can be miniaturized, it can generate a beam reduced particularly in the X direction (see Japanese Patent Application No. 2002-188579).

  The thickness of the trapezoidal column 4 in the Y direction is 600 nm, the apex angle of the tip is 30 °, and the length of the trapezoidal column 4 in the light traveling direction Z is 1.4 μm. A light confining portion 6 is formed in the vicinity of the tip portion of the trapezoidal column 4.

  As will be described in detail later, the light confinement portion 6 is formed of a diamond layer 8 disposed in the center and a pair of Si layers 10 disposed adjacent to both sides of the diamond layer 8.

  To further reduce the beam diameter, enclosing the dielectric with a material (for example, metal) that has a negative dielectric constant at the wavelength used has the same effect as increasing the refractive index of the dielectric inside. Therefore, the trapezoidal column 4 is surrounded by aluminum (Al) 12.

  Since the real part of the dielectric constant of aluminum at the wavelength used is -23.38 and the dielectric constant of diamond is 6.1, the condition of plasmon excitation, that is, the material having a negative dielectric constant at the wavelength used, is used. It is satisfied that the absolute value of the real part of the dielectric constant is larger than the dielectric constant of the adjacent dielectric.

  FIG. 4 and FIG. 5 show computer simulation images of the state of light propagation when light is incident on a diamond trapezoidal column that does not have the light confining portion 6 in the vicinity of the tip. FIG. 4 shows the state of light propagation in the X direction, and FIG. 5 shows the state of light propagation in the Y direction, showing how the light interferes in both the X direction and the Y direction.

The exit surface 14 is selected so that the light interferes most on the exit surface 14 and the beam is miniaturized. At this time, the beam size of 1 / e ² at 10 nm from the emission surface 14 is 100 nm in the X direction and 600 nm in the Y direction. In the X direction, the beam is miniaturized by the interference effect. It can be seen that further refinement of the beam is necessary.

  For such unidirectional beam reduction, the beam confinement in the X direction can be reduced without disturbing the condensing property in the X direction by utilizing the confinement of the beam with the less periodic structure of the present invention. .

  FIG. 6 shows a cross-sectional example of a comparative example of the trapezoidal column optical head 16 having only one light transmission part (slit or opening) 18 at the center. Similar to FIG. 3, the trapezoidal column 4 is made of diamond, and the light transmitting portion 18 provided at the center of the light emitting portion is formed of diamond similar to the trapezoidal column 4 and has a thickness of 25 nm.

  A pair of Si layers 20 are formed adjacent to both sides of the light transmission portion 18. Reference numeral 22 denotes an Al layer having a thickness of 200 nm surrounding the trapezoidal pillar 4 and the Si layer 20. In this configuration, as shown in the computer simulation image of FIG. 7, the light cannot pass through the slit 18 having a wavelength equal to or smaller than the wavelength of the light to be used, and the light is not emitted from the emission surface 14.

  Referring to FIG. 8, a cross-sectional view of a trapezoidal column optical head 24 of another comparative example is shown. In this comparative example, the trapezoidal pillar 4 is also made of diamond, and a plurality of slits 26 and a plurality of Si layers 28 adjacent to both sides of each slit 26 are formed.

  Both the slit 26 and the Si layer 28 have a thickness of 25 nm. The slit 26 is made of diamond. The periphery of the trapezoidal pillar 4 and the Si layer 28 is surrounded by an Al layer 22 having a thickness of 200 nm.

  It has been found that when light is incident on the optical head 24 of this comparative example, the light can pass through the slit 26 having a thickness of 25 nm without being attenuated, as shown in the computer simulation image of FIG. However, in this state, a large number of fine beams are emitted from the emission surface 14.

  On the other hand, when the period interval is widened by the multilayer periodic structure as shown in FIG. 8, the phenomenon that light cannot be transmitted through the light transmission part (opening) was also found by the same electromagnetic field calculation. From this calculation result, only the center is a transmission part (aperture) formed of a dielectric material with a low refractive index, and a dielectric layer with a high refractive index is arranged on both sides of the aperture, and the pitches of other diffraction gratings are It was found that by expanding or changing the refractive index, a fine light beam having a wavelength shorter than the wavelength to be used is confined in the central light confinement portion, and this single light beam is emitted from the emission surface.

  FIG. 10 is a cross-sectional view along the Y direction of the optical head 2 of the first embodiment shown in FIG. The central first dielectric layer 8 serving as a light transmission part (opening) is formed of the same diamond as the trapezoidal pillar 4 and has a thickness of 20 nm.

A pair of second dielectric layers 10 made of Si and having a thickness of 25 nm are disposed adjacent to both sides of the first dielectric layer 8. A pair of 40 nm thick third dielectric layers 30 made of SiO ₂ are disposed adjacent to each second dielectric layer 10.

  Further, a pair of fourth dielectric layers 32 made of Si and having a thickness of 120 nm are disposed adjacent to the third dielectric layers 30. The trapezoidal pillar 4 and the fourth dielectric layer 32 are surrounded by the Al layer 12 having a thickness of 200 nm. The length of the multilayer structure in the Z direction is 100 nm. The first dielectric layer 8 and the third dielectric layer 30 are transparent to the light used.

  Computer simulation images of the state of light propagation according to the first embodiment are shown in FIGS. FIG. 11 is a simulation image in the Y direction, and FIG. 12 is a simulation image in the X direction.

  As is apparent from FIGS. 11 and 12, light propagates while increasing the intensity without attenuating the central opening 8 having a thickness of 20 nm. FIG. 13 shows the beam profile at a position 10 nm away from the emission surface 14 at this time.

The 1 / e ² beam diameter at a position 10 nm from the emission surface is extremely miniaturized to 100 nm in the X direction, 86 nm in the Y direction, and 66 × 40 nm in the full width at half maximum. The ratio of the amount of emitted light to the amount of light incident on the optical head at this time, that is, the light utilization efficiency was as high as 2.4%, and sufficient characteristics were obtained as an optical head for a large capacity optical storage.

  In this embodiment, since the refractive index difference Δn between adjacent dielectric layers is large, sufficient light utilization efficiency can be achieved even if the total number of laminated structures is small. However, the light cannot pass through the optical head as shown in FIG. 7 simply by sandwiching the low refractive index dielectric layer disposed at the center between the pair of high refractive index dielectric layers.

  On the other hand, in the case of a multilayer structure having three periods as in this embodiment, light propagates with increasing intensity without being attenuated in the central opening, and is emitted from the emission end face. However, it should be noted that the three periodic structures have a special periodicity in which the length of the period (pitch) or the refractive index differs between the center combination and the combination on both sides. In the present embodiment, the Al layer 12 surrounds the periphery, but transmitted light having high intensity can be obtained without using the Al layer 12.

In the first embodiment described above, the first dielectric layer 8 is formed from diamond, the second dielectric layer 10 and the fourth dielectric layer 32 are formed from Si, and the third dielectric layer 30 is formed from SiO _2. However, the material of each dielectric layer is not limited to this.

  That is, the second dielectric layer 10 and the fourth dielectric layer 32 have a higher refractive index than the first dielectric layer 8, and the third dielectric layer 30 has a refractive index different from that of the first dielectric layer 8, or It is sufficient that the thicknesses are different from each other.

  Preferably, the third dielectric layer 30 has a smaller refractive index than the first dielectric layer 8. As an alternative, the third dielectric layer 30 is preferably thicker than the first dielectric layer 8. Further, the difference in refractive index between the first dielectric layer 8 and the second dielectric layer 10 is preferably 2 or more.

  Here, it is possible to change the refractive index by changing the material of the dielectric layer. The difference in refractive index between the low refractive index dielectric layer and the high refractive index dielectric layer may be 0.1 or more, but a larger refractive index difference is more effective. The difference in thickness of the dielectric layer may be as small as possible. Specifically, it is effective to select the thickness within the range of several nm to several hundred nm.

  A diffraction grating having a laminated structure as in this embodiment can be regarded as a one-dimensional photonic crystal in a broad sense, but light transmission increases when the polarization direction of incident light is orthogonal to the layer lamination direction, The light transmittance depends on the polarization direction of incident light.

In such a transmission phenomenon, in general, the intensity of antinodes and nodes appear in the transmitted light almost periodically in the traveling direction, and the period is approximately λ / 2n, where n is the refractive index of the medium through which the light is transmitted. There are many so-called Fabry-Perot resonance modes. Examples of the material having a high refractive index and low loss include KNbO ₃ , LiNbO ₃ , AgBr, TlCl, ZnS, KPS-6, ESO, and TiO ₂ .

  In the above description, an element (optical head) having a special periodic structure is described in the trapezoidal column 4. However, the present invention is not limited to the trapezoidal column shape, and parallel light that can be generated by a normal lens or the like. Even if a convergent spherical wave or the like is incident on an element having a special periodic structure as described above, the beam can be significantly reduced in one direction.

Referring to FIG. 14, there is shown a sectional view of an optical head 2A according to a second embodiment of the present invention. In this embodiment, the third dielectric layer 30 is deleted a predetermined distance from the emission end face. If the third dielectric layer 30 is formed of SiO ₂ and its thickness is W, the third dielectric layer 30 is deleted to about W in the depth direction by etching SiO ₂ . W is about 50 to 100 nm. Thereby, weak light leakage from the third dielectric layer 30 can be prevented.

  Referring to FIG. 15, there is shown a perspective view of the optical head 34 according to the third embodiment of the present invention. 16 is a cross-sectional view taken along the Y direction in FIG. The trapezoidal column 36 includes a pair of trapezoidal main surfaces 36a parallel to each other, a rectangular bottom surface 36b, a rectangular top surface 36c parallel to the rectangular bottom surface 36b, a top surface 36c, a bottom surface 36b, and a pair of trapezoidal main surfaces. It has a pair of inclined side surfaces 36d that connect 36a to each other. The apex angle of the trapezoidal column 36 is 30 °. In the present embodiment, the multilayer film is present over the entire length of the optical head (optical element) 34.

In the cross-sectional view of FIG. 16, reference numeral 40 denotes a first dielectric layer formed of SiO ₂ having a thickness of 20 nm disposed in the center of the optical head 34, and adjacent to both sides of the first dielectric layer 40. A pair of first metal layers 42 formed of Al having a thickness of 30 nm are disposed.

  A pair of second dielectric layers 44 made of diamond each having a thickness of 160 nm are disposed adjacent to each first metal layer 42. Further, a pair of second metal layers 38 made of Al each having a thickness of 200 nm are disposed adjacent to each second dielectric layer 44.

  Thus, in this embodiment, metal is used as a member that blocks light. At this time, in order to increase the light intensity by resonance of metal free electrons at the wavelength used, it is necessary for the first metal layer 42 and the second metal layer 38 to satisfy the condition in which plasmons exist.

  That is, the absolute value of the real part of the dielectric constant of the metal needs to be larger than the dielectric constant of the adjacent dielectric. In the present embodiment, aluminum (Al) that satisfies this condition is used as the first and second metal layers. The first dielectric layer 40 and the second dielectric layer 44 are transparent to the light used.

  FIG. 17 and FIG. 18 show computer simulation images of light propagation when light is incident on the optical head 34 of the third embodiment. FIG. 17 is a simulation image in the Y direction, and FIG. 18 is a simulation image in the X direction.

  As is apparent from FIGS. 17 and 18, light passes through the very fine first dielectric layer 40 having a thickness of 20 nm without being attenuated. FIG. 19 shows a beam profile at a position emitted 10 nm from the emission surface at this time.

The 1 / e ² beam diameter at a position 10 nm from the emission surface is 100 nm in the X direction and 71 nm in the Y direction, and the full width at half maximum is 65 × 37 nm. The light utilization efficiency of this embodiment is as high as 0.94%, and sufficient characteristics were obtained as an optical head for large-capacity storage.

  In the third embodiment described above, each metal layer is made of aluminum, but other metals having a negative dielectric constant can also be used. The absolute value of the real part of the dielectric constant of the metal needs to be larger than the dielectric constant of the adjacent dielectric layer. Preferably, the second dielectric layer 44 has a higher refractive index than the first dielectric layer 40. Alternatively, the second dielectric layer 44 has a greater thickness than the first dielectric layer 40.

  As a modification of the present embodiment, a dielectric laminated structure as in the first and second embodiments may be used. Furthermore, as a modification of the first and second embodiments, a metal layer such as aluminum (Al) may be used as a member that blocks light.

FIG. 20 is a schematic sectional view of an optical head 46 according to the fourth embodiment of the present invention. This embodiment is an embodiment in which the number of periods of the laminated structure is increased. The first dielectric layer 48 disposed in the center is made of diamond, the second dielectric layer 50 is made of Si, the third dielectric layer 52 is made of SiO ₂ , and the fourth dielectric layer 54 is made of Si. It is formed.

That is, the laminated structure of the first to fourth dielectric layers is the same as that of the first embodiment shown in FIG. In the present embodiment, the fifth dielectric layer 56 is further formed of Si, and the sixth dielectric layer 58 is formed of Si. The seventh dielectric layer 60 is formed of SiO _2, 8 dielectric layer 62 is formed from Si.

  One of the features of the optical head 46 of the present embodiment is that the fifth dielectric layer 56 is formed of a highly refractive material and attempts to prevent light from passing through this portion. In manufacturing, the fourth to sixth dielectric layers 54-58 are of course formed in a single film formation step.

  In the present embodiment, when the light passes through a plurality of slits in FIG. 9, there is a phenomenon in which light is strongly transmitted through the third from the center. In this case, there is an advantage that the transmission intensity can be increased by increasing the number of periods of the diffraction grating. Instead of the fifth dielectric layer 56, a metal material having a negative dielectric constant may be used.

  Referring to FIG. 21, there is shown a schematic configuration diagram of an information recording / reproducing apparatus 64 using the optical head of the present invention. This information recording / reproducing apparatus 64 is an optically assisted magnetic recording / reproducing apparatus. The magnetic recording medium 66 rotates in the direction of arrow R.

  A reproducing magnetic sensor head 72 and the optical head 2 are formed between the lower magnetic shield 68 and the upper magnetic shield / lower core 70. Light is incident on the optical head 2 through the optical waveguide 74. An information writing coil 76 is formed on the lower core 70. Reference numeral 78 denotes an upper core.

  In the information recording / reproducing apparatus 64, the mark passes through the reproducing magnetic sensor head 72, the optical head 2, and the magnetic field generating coil 76 by the rotation of the magnetic recording medium 66. At the time of writing information, the light 3 emitted from the optical head 2 is irradiated onto the magnetic recording medium 66 to raise the temperature of the magnetic recording medium 66, and immediately thereafter, information is written by the magnetic field 80 generated by the coil 76. Information can be written to the magnetic recording medium 66 with a small magnetic field strength. The information recording / reproducing apparatus 64 can be manufactured as a complete integrated head by a wafer processing process.

  The optically assisted magnetic recording / reproducing apparatus has been described as the information recording / reproducing apparatus. However, the application of the optical head of the present invention is not limited to this, and a minute beam spot can be formed. It can also be applied to an optical head of a magneto-optical disk apparatus.

  In particular, in the case of a magneto-optical disk device, so-called crescent recording can be performed in the circumferential direction by magnetic field laser pulse modulation, and the recording length can be shortened, so that a high recording density can be achieved. In addition, overwrite recording can be performed by magnetic field laser pulse modulation, and high-speed recording and reproduction can be performed.

  FIG. 22 shows still another embodiment of the present invention. The light beam is condensed by the objective lens 82 and enters the solid immersion lens 84, and is further condensed by the solid immersion lens 84. The solid immersion lens 84 is a hemispherical lens, and a cylindrical optical head 86 according to the fifth embodiment is formed on a flat portion thereof.

As shown in FIG. 23, the cylindrical optical head 86 is formed of, for example, a first dielectric 88 formed of diamond, for example, at the center, and Si, for example, disposed on the outer periphery adjacent to the first dielectric 88. The ring-shaped second dielectric 90, the ring-shaped third dielectric 92 made of, for example, SiO ₂ disposed on the outer periphery adjacent to the second dielectric 90, and the third dielectric 92. And a ring-shaped fourth dielectric 94 made of, for example, Si, disposed on the outer periphery thereof.

The cylindrical optical head 86 further includes a ring-shaped fifth dielectric 95 made of SiO ₂ disposed on the outer periphery adjacent to the fourth dielectric 94 and an outer periphery adjacent to the fifth dielectric 95. It includes a ring-shaped sixth dielectric 96 made of Si.

As a modification of the cylindrical optical head 86 in FIG. 23, the central portion 88 is formed from SiO ₂ , the ring-shaped portions 90, 94, 96 are formed from a metal such as aluminum, and the ring-shaped portions 92, 95 are formed from diamond. You may make it do. In the fifth embodiment shown in FIG. 23, the beam can be reduced in all directions.

FIG. 24 shows an optical head 98 according to a sixth embodiment of the present invention, in which a rectangular parallelepiped 100 made of diamond is arranged at the center of a cylindrical body 102 made of Si, and is formed of SiO ₂ in a lattice shape around it. The rectangular parallelepiped 104 is arranged.

The cylindrical body 102 may be formed from a metal such as aluminum. In this case, it is preferable that the central rectangular parallelepiped 100 is made of SiO ₂ and the rectangular parallelepiped 104 arranged in a lattice shape is made of diamond.

FIG. 25 shows an optical head 98A according to a modification of the sixth embodiment shown in FIG. In this modification, in addition to the rectangular parallelepiped 104 in FIG. 24, four rectangular parallelepipeds 106 made of the same SiO ₂ as the rectangular parallelepiped 104 are formed. In the embodiment shown in FIGS. 24 and 25, the X-direction and Y-direction co-beams can be reduced.

  FIG. 26 shows an optical head 108 according to a seventh embodiment of the present invention, in which two orthogonal diffraction gratings 110 and 112 are laminated. Also in this embodiment, the X-direction and Y-direction co-beams can be reduced.

  FIG. 27 shows a configuration diagram in which the embodiment shown in FIG. 22 is applied to, for example, a magneto-optical disk apparatus. A magnetic field modulation coil 118, a solid immersion lens 84, and a cylindrical optical head 86 are formed on the slider 114 supported by the suspension 116.

  Reference numeral 120 denotes a magneto-optical disk medium. A laser beam emitted from a laser diode (LD) 122 is collimated by a collimator lens 124, then passes through a polarization beam splitter 126, and is magneto-optical disk by an objective lens 128, a solid immersion lens 84 and a cylindrical optical head 86. It is condensed on the medium 120.

  At the time of writing information, the magnetic field modulation coil 118 is modulated according to the data to be written, and the data is written to the magneto-optical disk medium 120. At the time of reading information, the reflected light from the magneto-optical disk medium 120 is reflected by the polarization beam splitter 126 and condensed on the light detection element 132 by the lens 130, and the magneto-optical signal is detected.

  By producing the optical element (optical head) of the present invention on the exit surface of an LD or LED, the light condensing property can be improved, and an efficient optical device can be manufactured. Further, by forming the optical element of the present invention on the end face of the optical waveguide, it can be used as a coupling element such as a coupling with a communication optical fiber or an optical wiring.

  28A to 28C show an example of a method for manufacturing the optical head 2 of the first embodiment shown in FIG. First, as shown in FIG. 28A, an Al layer 136 and a multilayer structure 138 are formed by sputtering, vacuum deposition, or CVD.

  Next, as shown in FIG. 28B, a light-transmitting portion 140 of a trapezoidal column made of diamond is formed. Finally, as shown in FIG. 28C, Al 142 is deposited on the multilayer structure 138 and the trapezoidal pillar 140.

  29A to 29D show an example of a method for manufacturing the optical head 34 of the third embodiment shown in FIG. First, as shown in FIG. 29A, a multilayer film is formed by RF sputtering, vacuum deposition, or CVD. Next, as shown in FIG. 29B, after applying a photoresist, the trapezoid 144 is patterned using a stepper, an electron beam direct writing apparatus, or the like.

  Next, as shown in FIG. 29C, the shape is finished by reactive ion etching (RIE) or the like, and finally, the outermost Al layer 146 is formed as shown in FIG. 29D. These manufacturing processes are performed by a wafer process, and finally, each chip is cut and polished so that a predetermined surface appears.

The apex angle of the trapezoidal column in each of the embodiments described above can be appropriately selected in the range of 10 ° to 120 ° according to the manufacturing surface and the beam design. Moreover, the material of each layer of each embodiment can be appropriately selected according to the manufacturing surface, material cost, and beam design, and is not limited to the material of each embodiment. For example, SiO ₂ based materials containing SiO ₂ may not be SiO _2, may be an Al-based material containing Al.

  Since the optical head of the present invention can emit a minute light beam as described above in detail, when applied to an information recording / reproducing apparatus, ultra-high density recording can be realized. Further, an optical head capable of emitting a light beam that is easily reduced in a two-dimensional pattern formed on a substrate can be manufactured, and mass production of the optical head is possible.

  Furthermore, since it can be manufactured by lithography technology together with a reproducing head, an optical head that can cope with high-density recording of subterabit per inch square or more and an information recording / reproducing apparatus using the same can be provided.

  Furthermore, the optical head of the present invention can be applied not only to an information storage device but also to an optical device such as an optical communication component or a semiconductor processing device.

  The present invention has the following supplementary notes.

(Supplementary note 1) a first dielectric layer having a first refractive index;
A pair of second dielectric layers disposed adjacent to both sides of the first dielectric layer and having a second refractive index greater than the first refractive index;
A pair of third dielectric layers disposed adjacent to each of the second dielectric layers;
A pair of fourth dielectric layers disposed adjacent to each of the third dielectric layers and having a third refractive index greater than the first refractive index;
An optical head characterized in that light is incident from a direction orthogonal to a stacking direction of the first to fourth dielectric layers.

  (Supplementary note 2) The optical head according to supplementary note 1, wherein the first and third dielectric layers have different refractive indexes.

  (Supplementary note 3) The optical head according to supplementary note 2, wherein each of the third dielectric layers has a fourth refractive index smaller than the first refractive index.

  (Supplementary note 4) The optical head according to supplementary note 1, wherein the second dielectric layer and the fourth dielectric layer are formed of the same dielectric.

  (Supplementary note 5) The optical head according to supplementary note 1, wherein the first and third dielectric layers have different thicknesses.

  (Supplementary note 6) The optical according to supplementary note 5, wherein the first dielectric layer has a first thickness, and each of the third dielectric layers has a second thickness larger than the first thickness. head.

  (Supplementary note 7) The optical head according to supplementary note 1, wherein the first to fourth dielectric layers have different thicknesses.

(Supplementary note 8) The optical head according to supplementary note 1, wherein the second and fourth dielectric layers are made of silicon, and the third dielectric layer is made of SiO ₂ .

(Supplementary Note 9) A pair of fifth dielectric layers formed of the same dielectric material as the third dielectric layer, disposed adjacent to each of the fourth dielectric layers,
5. The optical head according to appendix 4, further comprising a pair of sixth dielectric layers made of the same dielectric as the second dielectric layer, disposed adjacent to each of the fifth dielectric layers.

  (Supplementary note 10) The optical head according to supplementary note 9, wherein each of the fourth dielectric layers has a thickness greater than each of the second dielectric layers.

(Supplementary Note 11) The optical head has an incident end face on which light is incident and an outgoing end face on which light is emitted,
The optical head according to appendix 1, wherein each of the third dielectric layers is deleted by a predetermined distance on the emission end face side.

  (Supplementary note 12) The optical head according to supplementary note 1, wherein the incident light is linearly polarized light having a polarization plane in a direction orthogonal to a stacking direction of the first to fourth dielectric layers.

(Supplementary note 13) a first dielectric layer;
A pair of first adjacent layers having a negative dielectric constant, disposed adjacent to both sides of the first dielectric layer;
A pair of second dielectric layers disposed adjacent to each of the first adjacent layers;
A pair of second adjacent layers having a negative dielectric constant disposed adjacent to each of the second dielectric layers;
The first and second dielectric layers have different refractive indices or different thicknesses;
An optical head, wherein light is incident from a direction orthogonal to the stacking direction of the layers.

  (Supplementary Note 14) The first dielectric layer has a first refractive index, and each of the second dielectric layers has a second refractive index larger than the first refractive index. The optical head described.

  (Supplementary note 15) The supplementary note 13, wherein the first dielectric layer has a first thickness, and each of the second dielectric layers has a second thickness greater than the first thickness. Optical head.

  (Supplementary note 16) The optical head according to supplementary note 13, wherein the first and second dielectric layers and the first and second adjacent layers have different thicknesses.

  (Additional remark 17) The said 1st and 2nd adjacent layer is an optical head of Additional remark 13 currently formed from the same metal material.

(Supplementary Note 18) The first dielectric layer is formed from SiO _2, the first and second adjacent layers optical head according to Supplementary Note 17, wherein the formed aluminum.

(Supplementary note 19) A pair of third dielectric layers disposed adjacent to each of the second adjacent layers;
14. The optical head according to appendix 13, further comprising a pair of third adjacent layers disposed adjacent to each of the third dielectric layers.

  (Additional remark 20) The said 1st thru | or 3rd adjacent layer is formed from the same metal material, Each said 2nd adjacent layer has thickness thicker than the thickness of the said 1st adjacent layer. head.

(Supplementary note 21) The optical head has an incident end face on which light is incident and an outgoing end face on which light is emitted,
14. The optical head according to appendix 13, wherein each of the second dielectric layers has the emission end face side removed by a predetermined distance.

  (Supplementary note 22) The optical head according to supplementary note 13, wherein the incident light is linearly polarized light having a polarization plane in a direction orthogonal to a stacking direction of the layers.

(Supplementary Note 23) A cylindrical optical head,
A first dielectric having a first refractive index disposed in the center;
A ring-shaped second dielectric having a second refractive index greater than the first refractive index, disposed adjacent to the first dielectric and on an outer periphery thereof;
A ring-shaped third dielectric disposed on the outer periphery adjacent to the second dielectric;
A ring-shaped fourth dielectric having a third refractive index greater than the first refractive index, disposed adjacent to the third dielectric and on an outer periphery thereof;
An optical head characterized in that light is incident in the axial direction of a cylindrical optical head.

(Supplementary Note 24) A cylindrical optical head,
A first dielectric disposed in the center;
A ring-shaped first adjacent material having a negative dielectric constant disposed on the outer periphery adjacent to the first dielectric;
A ring-shaped second dielectric disposed on the outer periphery adjacent to the first adjacent material;
A ring-shaped second adjacent material having a negative dielectric constant and disposed on the outer periphery adjacent to the second dielectric,
The first and second dielectrics have different refractive indices or different thicknesses;
An optical head, wherein light parallel to an axial direction of a cylindrical optical head is incident.

(Supplementary Note 25) A pair of trapezoidal principal surfaces parallel to each other, a rectangular bottom surface, a rectangular top surface parallel to the rectangular bottom surface, the top surface, the bottom surface, and the pair of trapezoidal principal surfaces, respectively. An optical head having a pair of inclined side surfaces to be connected,
A first dielectric layer having a first refractive index and parallel to the trapezoid main surface;
A pair of second dielectric layers disposed adjacent to both sides of the first dielectric layer and having a second refractive index greater than the first refractive index;
A pair of third dielectric layers disposed adjacent to each of the second dielectric layers;
A pair of fourth dielectric layers disposed adjacent to each of the third dielectric layers and having a third refractive index greater than the first refractive index;
An optical head, wherein light is incident on the rectangular bottom surface from a direction orthogonal to the bottom surface.

(Supplementary Note 26) A pair of trapezoidal principal surfaces parallel to each other, a rectangular bottom surface, a rectangular top surface parallel to the rectangular bottom surface, the top surface, the bottom surface, and the pair of trapezoidal principal surfaces, respectively. An optical head having a pair of inclined side surfaces to be connected,
A first dielectric layer parallel to the trapezoidal principal surface;
A pair of first adjacent layers having a negative dielectric constant, disposed adjacent to both sides of the first dielectric layer;
A pair of second dielectric layers disposed adjacent to each of the first adjacent layers;
A pair of second adjacent layers having a negative dielectric constant disposed adjacent to each of the second dielectric layers;
The first and second dielectric layers have different refractive indices or different thicknesses;
An optical head, wherein light is incident on the rectangular bottom surface from a direction orthogonal to the bottom surface.

(Supplementary note 27) a hemispherical solid immersion lens having a plane;
A cylindrical optical element formed on the plane of the solid immersion lens,
The cylindrical optical element is
A first dielectric having a first refractive index and disposed in the center;
A ring-shaped second dielectric having a second refractive index greater than the first refractive index, disposed adjacent to the first dielectric and on an outer periphery thereof;
A ring-shaped third dielectric disposed on the outer periphery adjacent to the second dielectric;
A ring-shaped fourth dielectric having a third refractive index greater than the first refractive index, disposed adjacent to the third dielectric and on an outer periphery thereof;
An optical head characterized in that light parallel to the axial direction of the cylindrical optical element is incident on the solid immersion lens.

(Supplementary note 28) a hemispherical solid immersion lens having a plane;
A cylindrical optical element formed on the plane of the solid immersion lens,
The cylindrical optical element is
A first dielectric disposed in the center;
A ring-shaped first adjacent material having a negative dielectric constant disposed on the outer periphery adjacent to the first dielectric;
A ring-shaped second dielectric disposed on an outer periphery adjacent to the ring-shaped first adjacent material;
A ring-shaped second adjacent material having a negative dielectric constant, disposed adjacent to the ring-shaped second dielectric,
The first and second dielectrics have different refractive indices or different thicknesses;
An optical head characterized in that light parallel to the axial direction of the cylindrical optical element is incident on the solid immersion lens.

(Supplementary note 29) A cylindrical first dielectric having a first refractive index;
A rectangular parallelepiped second dielectric having a second refractive index smaller than the first refractive index embedded in a central portion of the cylindrical first dielectric;
A plurality of rectangular parallelepiped third dielectrics having a third refractive index smaller than the first refractive index, embedded in a lattice in the cylindrical first dielectric around the second dielectric. Equipped,
An optical head, wherein light is incident from an axial direction of the cylindrical first dielectric.

(Supplementary Note 30) A cylindrical metal having a negative dielectric constant;
A rectangular parallelepiped first dielectric having a first refractive index embedded in a central portion of the cylindrical metal;
A plurality of rectangular parallelepiped second dielectrics having a second refractive index different from the first refractive index embedded in a lattice in the cylindrical metal around the first dielectric,
An optical head, wherein light is incident from an axial direction of the cylindrical metal.

(Supplementary Note 31) An information storage device for recording or reproducing information on a recording medium,
A light source that emits a light beam;
An optical head for irradiating a recording medium with light based on the light beam,
The optical head is
A first dielectric layer having a first refractive index;
A pair of second dielectric layers disposed adjacent to both sides of the first dielectric layer and having a second refractive index greater than the first refractive index;
A pair of third dielectric layers disposed adjacent to each of the second dielectric layers;
A pair of fourth dielectric layers disposed adjacent to each of the third dielectric layers and having a third refractive index greater than the first refractive index;
An information storage device, wherein light is incident on the optical head from a direction orthogonal to a stacking direction of the first to fourth dielectric layers.

(Supplementary note 32) An information storage device for recording or reproducing information on a recording medium,
A light source that emits a light beam;
An optical head for irradiating a recording medium with light based on the light beam,
The optical head is
A first dielectric layer;
A pair of first adjacent layers having a negative dielectric constant, disposed adjacent to both sides of the first dielectric layer;
A pair of second dielectric layers disposed adjacent to each of the first adjacent layers;
A pair of second adjacent layers having a negative dielectric constant disposed adjacent to each of the second dielectric layers;
The first and second dielectric layers have different refractive indices or different thicknesses;
An information storage device, wherein light is incident on the optical head from a direction orthogonal to the stacking direction of the layers.

FIG. 1 is a diagram for explaining the problems of the conventional minute aperture method. FIG. 2 is an explanation of the problems of the conventional bow-tie antenna system. FIG. 3 is a perspective view of the optical head according to the first embodiment of the present invention. FIG. 4 is a computer simulation image in the X direction when light is incident on a diamond trapezoidal column having no light confining portion in the vicinity of the tip. FIG. 5 is a computer simulation image in the Y direction when light is incident on a diamond trapezoidal column having no light confining portion in the vicinity of the tip. FIG. 6 is a cross-sectional view of a comparative example of a trapezoidal column optical head having only one transmission part in the center. FIG. 7 is a computer simulation image in the Y direction when light is incident on the comparative example of FIG. FIG. 8 is a cross-sectional view of a comparative example of a trapezoidal column optical head having a plurality of light transmission portions. FIG. 9 is a computer simulation image in the Y direction when light is incident on the comparative example of FIG. FIG. 10 is a cross-sectional view along the Y direction of the optical head according to the first embodiment of the present invention. FIG. 11 is a computer simulation image in the Y direction when light is incident on the optical head according to the first embodiment of the present invention. FIG. 12 is a computer simulation image in the X direction when light is incident on the optical head according to the first embodiment of the present invention. FIG. 13 shows a beam profile at a position 10 nm from the exit surface when light is incident on the optical head of the first embodiment. FIG. 14 is a sectional view taken along the Y direction of the optical head according to the second embodiment of the present invention. FIG. 15 is a perspective view of an optical head according to the third embodiment of the present invention. FIG. 16 is a cross-sectional view along the Y direction of the optical head of the third embodiment. FIG. 17 is a computer simulation image in the Y direction when light is incident on the optical head of the third embodiment. FIG. 18 is a computer simulation image in the X direction when light is incident on the optical head of the third embodiment. FIG. 19 shows a beam profile at a position of 10 nm from the exit surface when light is incident on the optical head of the third embodiment. FIG. 20 is a cross-sectional view of the optical head according to the fourth embodiment of the present invention along the Y direction. FIG. 21 is a schematic configuration diagram of an information recording / reproducing apparatus using the optical head of the present invention. FIG. 22 is a perspective view of an optical head according to another embodiment of the present invention. FIG. 23 is a perspective view of a cylindrical optical head of a fifth embodiment used for the optical head of another embodiment of FIG. FIG. 24 is a perspective view of an optical head according to a sixth embodiment of the present invention. FIG. 25 is a modified example of the optical head of the sixth embodiment. FIG. 26 is a perspective view of an optical head according to a seventh embodiment of the present invention. FIG. 27 is a schematic configuration diagram of an information recording / reproducing apparatus using the optical head of FIG. 28A to 28C are views showing a manufacturing process of the optical head of the first embodiment. FIGS. 29A to 29D are views showing a manufacturing process of the optical head of the third embodiment.

Claims (14)

A first dielectric having a first refractive index to be a light transmission portion;
A pair of second dielectrics disposed adjacent to both sides of the first dielectric and having a second refractive index greater than the first refractive index;
A pair of third dielectrics disposed adjacent to each of the second dielectrics;
A pair of fourth dielectrics disposed adjacent to each of the third dielectrics and having a third refractive index greater than the first refractive index;
The combined width of the two layers of the first dielectric and the second dielectric and the combined width of the two layers of the third dielectric and the fourth dielectric are equal to or less than the wavelength of incident light, and the first 1 width a combination of two layers of dielectric and the second dielectric is minor than the width of a combination of two layers of the fourth dielectric and the third dielectric,
The third dielectric and the fourth dielectric do not output the transmitted light of the incident light, and the first dielectric outputs the transmitted light of the incident light;
An optical head characterized by. A first dielectric serving as a light transmission portion;
A pair of first adjacent materials having a negative dielectric constant, disposed adjacent to both sides of the first dielectric;
A pair of second dielectrics disposed adjacent to each of the first adjacent materials;
A pair of second adjacent materials having a negative dielectric constant disposed adjacent to each of the second dielectrics;
The first and second dielectrics have different refractive indices or different thicknesses;
The combined width of the two layers of the first dielectric and the first adjacent material and the combined width of the two layers of the second dielectric and the second adjacent material are equal to or less than the wavelength of incident light, and the first The combined width of one dielectric and two layers of the first adjacent material is smaller than the combined width of the second dielectric and two layers of the second adjacent material,
The second dielectric and the second adjacent material do not output the transmitted light of the incident light, and the first dielectric outputs the transmitted light of the incident light,
The real part absolute value of the dielectric constant of the first adjacent material is larger than the dielectric constants of the first and second dielectrics, and the real part absolute value of the dielectric constant of the second adjacent material is the dielectric constant of the second dielectric. Greater than rate,
An optical head characterized by. The optical head according to claim 1.
Incident light is incident from a direction orthogonal to the stacking direction of the dielectrics, and is linearly polarized light having a polarization plane in a direction orthogonal to the stacking direction of the dielectrics. The optical head according to claim 2, wherein
The incident light is linearly polarized light that is incident from a direction orthogonal to the stacking direction of each dielectric and each adjacent material and has a polarization plane in a direction orthogonal to the stacking direction of each dielectric and the adjacent material. A featured optical head. A first dielectric body having a first refractive index that serves as a light transmission portion, and a cylindrical shape;
A ring-shaped second dielectric having a predetermined thickness and having a second refractive index larger than the first refractive index, disposed on the outer periphery of the first dielectric;
A ring-shaped third dielectric having a predetermined thickness disposed on the outer periphery of the second dielectric;
A ring-shaped fourth dielectric having a predetermined thickness and having a third refractive index larger than the first refractive index, disposed on the outer periphery of the third dielectric;
The length obtained by adding the diameter of the first dielectric and the thickness of the second dielectric and the length obtained by adding the thickness of the third dielectric and the thickness of the fourth dielectric are less than the wavelength of the incident light. and, the length plus the thickness of the second dielectric and the diameter of the first dielectric rather short than a length obtained by adding the thickness of the fourth dielectric and the thickness of the third dielectric,
The third dielectric and the fourth dielectric do not output the transmitted light of the incident light, and the first dielectric outputs the transmitted light of the incident light ;
An optical head characterized by. A cylindrical first dielectric material serving as a light transmission part;
A ring-shaped first adjacent member having a negative dielectric constant and having a predetermined thickness, disposed on the outer periphery of the first dielectric;
A ring-shaped second dielectric having a predetermined thickness disposed on the outer periphery of the first adjacent material;
A ring-shaped second adjacent material having a negative dielectric constant and having a predetermined dielectric constant disposed on the outer periphery of the second dielectric;
The refractive indexes of the first and second dielectrics are different from each other or the diameter of the first dielectric and the thickness of the second dielectric are different;
The length obtained by adding the diameter of the first dielectric and the thickness of the first adjacent material and the length obtained by adding the thickness of the second dielectric and the thickness of the second adjacent material are equal to or less than the wavelength of the incident light. The length of the first dielectric and the thickness of the first adjacent material is shorter than the length of the second dielectric and the thickness of the second adjacent material,
The second dielectric and the second adjacent material do not output the transmitted light of the incident light, and the first dielectric outputs the transmitted light of the incident light,
The real part absolute value of the dielectric constant of the first adjacent material is larger than the dielectric constants of the first and second dielectrics, and the real part absolute value of the dielectric constant of the second adjacent material is the dielectric constant of the second dielectric. Greater than rate,
An optical head characterized by. A pair of trapezoidal principal surfaces parallel to each other, a rectangular bottom surface, a rectangular top surface parallel to the rectangular bottom surface, and a pair of top surfaces, the bottom surface, and the pair of trapezoidal principal surfaces are connected to each other. An optical head having an inclined side surface,
A first dielectric that becomes a light transmissive portion, has a first refractive index, and is parallel to the trapezoidal main surface;
A pair of second dielectrics disposed adjacent to both sides of the first dielectric and having a second refractive index greater than the first refractive index;
A pair of third dielectrics disposed adjacent to each of the second dielectrics;
A pair of fourth dielectrics disposed adjacent to each of the third dielectrics and having a third refractive index greater than the first refractive index;
The combined width of the two layers of the first dielectric and the second dielectric and the combined width of the two layers of the third dielectric and the fourth dielectric are equal to or less than the wavelength of incident light, and the first 1 width a combination of two layers of dielectric and the second dielectric is minor than the width of a combination of two layers of the fourth dielectric and the third dielectric,
The third dielectric and the fourth dielectric do not output the transmitted light of the incident light, and the first dielectric outputs the transmitted light of the incident light;
An optical head characterized by. A pair of trapezoidal principal surfaces parallel to each other, a rectangular bottom surface, a rectangular top surface parallel to the rectangular bottom surface, and a pair of top surfaces, the bottom surface, and the pair of trapezoidal principal surfaces are connected to each other. An optical head having an inclined side surface,
A first dielectric parallel to the trapezoidal principal surface, which is a light transmitting portion;
A pair of first adjacent materials having a negative dielectric constant, disposed adjacent to both sides of the first dielectric;
A pair of second dielectrics disposed adjacent to each of the first adjacent materials;
A pair of second adjacent materials having a negative dielectric constant disposed adjacent to each of the second dielectrics;
The first and second dielectrics have different refractive indices or different thicknesses;
The combined width of the two layers of the first dielectric and the first adjacent material and the combined width of the two layers of the second dielectric and the second adjacent material are equal to or less than the wavelength of incident light, and the first The combined width of one dielectric and two layers of the first adjacent material is smaller than the combined width of the second dielectric and two layers of the second adjacent material,
The second dielectric and the second adjacent material do not output the transmitted light of the incident light, and the first dielectric outputs the transmitted light of the incident light,
The real part absolute value of the dielectric constant of the first adjacent material is larger than the dielectric constants of the first and second dielectrics, and the real part absolute value of the dielectric constant of the second adjacent material is the dielectric constant of the second dielectric. An optical head characterized by being larger than the rate. The optical head according to claim 5, wherein
Each of the dielectrics is formed on a plane of a hemispherical solid immersion lens. The optical head according to claim 6.
Each of the dielectrics and the adjacent members is formed on a plane of a hemispherical solid immersion lens. A first dielectric having a first refractive index and made of a cylindrical dielectric;
A second dielectric having a rectangular parallelepiped shape and having a second refractive index smaller than the first refractive index and embedded in a central portion of the cylindrical dielectric;
A third dielectric disposed around the second dielectric via the first dielectric and embedded in a lattice in the cylindrical dielectric;
The width of the second dielectric material in the X-axis direction perpendicular to the traveling direction of the incident light and passing through the center of the second dielectric material and parallel to one side of the rectangular parallelepiped and perpendicular to the one side, The width of the first dielectric located between the two dielectrics and the third dielectric is combined with the width of the first dielectric, and the width of the third dielectric and the third dielectric are separated from the second dielectric. The combined width of the first dielectric and the width of the first dielectric is less than or equal to the wavelength of the incident light, and the width of the second dielectric is between the second dielectric and the third dielectric. The width of the first dielectric located in the first dielectric is equal to the width of the third dielectric and the width of the first dielectric located farther from the second dielectric than the third dielectric. rather smaller than the width of the combined,
The first dielectric located farther from the second dielectric than the third dielectric and the third dielectric does not output the transmitted light of the incident light, and the second dielectric Output the transmitted light of the incident light,
An optical head characterized by. Having a negative dielectric constant, a cylindrical adjacent material, and
A first dielectric having a rectangular parallelepiped shape embedded in a central portion of the adjacent material, which is a light transmission portion;
A second dielectric disposed around the first dielectric via the adjacent material and embedded in a lattice in the cylindrical adjacent material;
The first and second dielectrics have different refractive indexes, or are perpendicular to the traveling direction of incident light, pass through the center of the first dielectric, and are parallel to one side of the rectangular parallelepiped and perpendicular to the one side. The widths of the first and second dielectrics in the Y-axis direction are different from each other;
A width of the first dielectric in the X axis parallel to one side of the rectangular parallelepiped and perpendicular to the traveling direction of the incident light and perpendicular to the one side, The width of the adjacent material located between one dielectric and the second dielectric, and the width of the second dielectric and the second dielectric are separated from the first dielectric. The combined width of the adjacent materials is less than or equal to the wavelength of the incident light, and the width of the first dielectric and the first dielectric and the second dielectric are positioned. The combined width of the adjacent materials is smaller than the combined width of the second dielectric and the adjacent material positioned away from the first dielectric than the second dielectric,
The adjacent material positioned farther from the first dielectric than the second dielectric and the second dielectric does not output the transmitted light of the incident light, and the first dielectric does not transmit the incident light. Outputs transmitted light,
The absolute value of the real part of the dielectric constant of the adjacent material is greater than the dielectric constant of the first and second dielectrics;
An optical head characterized by. An information storage device for recording or reproducing information on a recording medium,
A light source that emits a light beam;
An optical head for irradiating a recording medium with light based on the light beam,
The optical head is
A first dielectric that serves as a light transmitting portion and has a first refractive index;
A pair of second dielectrics disposed adjacent to both sides of the first dielectric and having a second refractive index greater than the first refractive index;
A pair of third dielectrics disposed adjacent to each of the second dielectrics;
A pair of fourth dielectrics disposed adjacent to each of the third dielectrics and having a third refractive index greater than the first refractive index;
The combined width of the two layers of the first dielectric and the second dielectric and the combined width of the two layers of the third dielectric and the fourth dielectric are equal to or less than the wavelength of incident light, and the first 1 width a combination of two layers of dielectric and the second dielectric is minor than the width of a combination of two layers of the fourth dielectric and the third dielectric,
The third dielectric and the fourth dielectric do not output the transmitted light of the incident light, and the first dielectric outputs the transmitted light of the incident light;
An information storage device. An information storage device for recording or reproducing information on a recording medium,
A light source that emits a light beam;
An optical head for irradiating a recording medium with light based on the light beam,
The optical head is
A first dielectric serving as a light transmission portion;
A pair of first adjacent materials having a negative dielectric constant, disposed adjacent to both sides of the first dielectric;
A pair of second dielectrics disposed adjacent to each of the first adjacent materials;
A pair of second adjacent materials having a negative dielectric constant disposed adjacent to each of the second dielectrics;
The first and second dielectrics have different refractive indices or different thicknesses;
The combined width of the two layers of the first dielectric and the first adjacent material and the combined width of the two layers of the second dielectric and the second adjacent material are equal to or less than the wavelength of incident light, and the first The combined width of one dielectric and two layers of the first adjacent material is smaller than the combined width of the second dielectric and two layers of the second adjacent material,
The second dielectric and the second adjacent material do not output the transmitted light of the incident light, and the first dielectric outputs the transmitted light of the incident light,
The real part absolute value of the dielectric constant of the first adjacent material is larger than the dielectric constants of the first and second dielectrics, and the real part absolute value of the dielectric constant of the second adjacent material is the dielectric constant of the second dielectric. Greater than rate,
An information storage device.

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