JP2000021005A - Proximity field optical head and optical recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a proximity field optical head, which mounts a proximity field optical light emitting probe having a high proximity field optical light emitting efficiency, and the optical recording and reproducing device using the head. SOLUTION: An optically transparent slider 1 conducts a relative motion while contacting an information recording medium 11 or floating with an approximately constant gap with the medium 11. A probe 3 is provided on the surface of the slider 1 facing the medium 11. The probe 3 has a quadrilateral pyramid having the surfaces that generate minute spot sized proximity field light beams 9 and are covered by metallic thin films 4. A pad 2 is also provided to control the contacting or floating condition of the medium 11. Thus, the optical recording and reproducing device having an ultra high recording density, a high transfer speed, a small size and a simple configuration is constructed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a near-field optical head and an optical recording / reproducing apparatus, and more particularly to a near-field optical head and an optical recording / reproducing apparatus equipped with a near-field light generating probe having high near-field light generating efficiency.

[0002]

2. Description of the Related Art In recent years, optical recording using near-field light has attracted attention as a method for achieving higher density of an optical disk device. For example, Applied Physics Letters, 6
Vol. 1, No. 2, pp. 142-144 (Applied
Physics Lettes, Vol. 62, No.
2, pp. 142-144, 1992), a probe in which the tip of an optical fiber is processed into a cone shape and a region other than the region of several tens of nanometers of the end of the optical fiber is covered with a metal coating, and this is used as a piezo element. There has been reported an example in which a recording mark having a diameter of 60 nm is recorded / reproduced on a platinum / cobalt multilayer film by controlling the position by mounting on a precision actuator used. In the case of this example, a shear force method using an atomic force is used for controlling the distance between the probe and the recording medium, and the recording density reaches 45 gigabits / square inch, which can be about 20 times the current state. . Furthermore,
Applied Physics Letters, Vol. 63, No. 26, pages 3550 to 3552 (Applied Physics Letters,
Vol. 63, No. 26, pp. 3550-3552, 1993) reported an example in which a neodymium-doped optical fiber was used to improve the S / N ratio using laser oscillation. I have. More recently, Applied Physics Letters,
Vol. 69, No. 19, pages 2612 to 2614 (Applied
physics Letters, Vol.69, No.19, pp.2612-2614,199
In (6), the apex angle of the optical fiber probe is changed in two steps, and the apex angle at the root portion is small and the apex angle at the tip portion is large, so that light leaks to the metal film for light shielding. It is described that a probe having high transmission efficiency can be obtained by pressing down and suppressing reflection from the probe tip. Applied Physics Letters, Vol. 71, 1
Issue 3 pages 1756 to 1758 (Applied physics Let
ters, Vol. 71, No. 13, pp. 1756-1758, 1997), the shape of an optical fiber probe is made asymmetrical with respect to the center line of the probe, and the surface plasma wave is excited to reduce the transmission efficiency. It is described that high probes can be obtained. Furthermore, in Program Number 4p-L-12 of the 58th Autumn Meeting of the Japan Society of Applied Physics, a 40 nm gold thin film was deposited on an optical fiber probe whose tip was processed into a cone shape, and this probe was subjected to total reflection conditions. Then, the light is inserted into the near-field region on the prism on which the light is incident, the output light from the optical fiber is detected, and the excitation of light by the localized plasma wave is observed. Furthermore, Physical Review, B, Vol. 55, No. 12, pages 7977 to 79.
Page 84 (Physical Review, B, Vol.55, No.12, pp.7977-
7984, 1997), into a piece of glass cut out into a triangular prism shape,
A gold thin film having a thickness of about 50 nm is deposited, and a glass piece is adhered on a prism. Then, a laser beam is irradiated on one vertex of the glass piece to excite a surface plasma wave. An example of developing a high resolution probe is described.

[0003]

However, the above conventional example has the following problems.

The conventional examples using an optical fiber are all attempts to obtain a probe for generating near-field light with high efficiency.
The light use efficiency is 0.01% to 0.1%, which is much smaller than the current light use efficiency of the optical information recording / reproducing device of several tens%. For this reason, the recording / reproducing speed of information cannot be made as high as that of the current device. In order to obtain the optical power required for the current transfer speed of optical information recording / reproduction, it is necessary to input a large laser light power. And the metal film covering the probe is damaged. In an optical information recording / reproducing device,
In order to increase the information transfer speed, it is necessary to increase the relative speed between the recording medium and the optical head for recording and reproducing information.

However, since the shear force method using atomic force is used for controlling the distance between the optical fiber probe and the recording medium, the distance between the recording medium and the fiber probe is determined by using a scanning force microscope. Needs to be controlled very precisely. Therefore, when the disk on which information is recorded is rotated at a high speed, the fluctuation of the distance between the probe and the high-frequency substrate caused by the eccentricity of the disk cannot be controlled, and the transfer speed cannot be increased.

The prior art using a glass piece on which the above-mentioned metal thin film is deposited as a probe is also an attempt to obtain a probe for generating near-field light with high efficiency, but the light utilization efficiency is about 0.1%. The light utilization efficiency of the current optical information recording / reproducing device is much smaller than that of several tens%. Furthermore, control by a scanning tunneling microscope is used to control the distance between the probe and the recording medium, and when the disk on which information is recorded is rotated at high speed, the distance between the probe and the high-frequency substrate caused by the eccentricity of the disk is also increased. However, there is a problem that the transfer speed cannot be increased because the fluctuation of the data cannot be controlled.

An object of the present invention is to provide a near-field light generating probe having high near-field light generating efficiency in order to increase the information transfer speed of an ultra-high density optical recording / reproducing apparatus to which the near-field light generating probe is applied. An object of the present invention is to provide a near-field optical head mounted thereon and an optical recording / reproducing apparatus using the same.

[0008]

To solve the above problems, the following means are employed.

A probe that generates relative-field light having a minute spot size on the information recording medium by making relative movement while in contact with the information recording medium or while floating at a substantially constant interval; In a near-field optical head having a laser light source for providing irradiation light for generating light and a means for condensing the laser light to the probe, the probe has a quadrangular pyramid shape, and the probe is made of an optically transparent material. And the entire probe surface was covered with a metal film. Furthermore, the polarization direction of the laser light was set to a direction parallel to a plane connecting two apexes of the quadrangular pyramid-shaped probe and the bottom surface facing each other. Further, a mechanism for adjusting the incident angle of the laser beam on the bottom surface of the quadrangular pyramid-shaped probe is provided.

Further, in the near-field optical head, the dielectric constant e1 at the wavelength L of the laser light, the laser light wavelength L of the optically transparent substance forming the probe, and the laser light of the metal film covering the entire surface of the probe. Real part e2, imaginary part e3 and film thickness d of the dielectric constant at the wavelength L, the incident angle q of the laser light on the bottom surface of the quadrangular pyramid-shaped probe, the top of the triangle in a plane parallel to the incident surface of the laser light. Half angle s1 of the angle, half angle s2 of the vertex angle of a triangle in a plane perpendicular to the laser light incident surface
Is a material and a shape that substantially satisfy (Equation 1).

[0011]

(Equation 1)

Further, in particular, the metal covering the probe surface is any one of gold, silver, chromium and aluminum. Further, the means for condensing the laser light on the probe is a condensing lens, and the numerical aperture thereof is at least 0.6 or more, and the spot diameter of the laser light condensed on the probe is at least 1 micron or less. .

Further, in the near-field optical head, the probe is formed on an optically transparent slider which makes relative movement while being in contact with the information recording medium or while floating at a substantially constant interval. Further, in the near-field optical head, a columnar pad provided on the slider to control the contact or floating state of the information recording medium, and a cone-shaped probe for generating a near-field light of a minute spot size Was provided in close proximity. Alternatively, in the near-field optical head, a cantilever in which an optically transparent probe is covered with a metal film is used as a probe.

Further, an optical recording / reproducing apparatus is constituted by the above-described near-field optical head, an optical recording medium, and a light receiving means for detecting a modulation signal of the near-field light generated by the near-field optical head by the recording medium.

Further, as the modulation signal of the near-field light by the recording medium, the reflected light from the probe is used. Further, in the optical recording / reproducing apparatus, a means for condensing the illumination light to the probe, a means for detecting a shift between the focus position of the illumination light condensed by the light condensing means and the probe position, and a relative position between the light condensing means and the probe A movable mechanism for correcting the position is provided. Furthermore, in the optical recording and reproducing apparatus,
And a movable mechanism for correcting the relative position of the light condensing means and the probe is separated from other components constituting the optical information recording / reproducing apparatus, and the light condensing means is mounted on a movable mechanism for accessing a predetermined position of the recording medium. did.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and FIG.
FIG. 1 is a perspective view of the near-field optical head of the present invention, and FIG. 1B is a cross-sectional view taken along ABC in FIG. 1A.

In FIG. 1A, reference numeral 1 denotes a slider made of an optically transparent substance. In this embodiment, the wavelength 650
Since the case where the semiconductor laser of nm is used as the light source is described, quartz is selected as the material of the slider, but the material is not limited to quartz. 2 is a slider information recording medium 11
This is a pad provided to control the state of floating from the surface. In this embodiment, three pads are provided on the bottom surface of the slider. A quadrangular pyramid probe 3 for generating near-field light adjacent to one of the pads and inside the pad 3
Is provided. The probe 3 is coated with a metal thin film 4 having a thickness of several tens nm as shown in FIG. A thin film for preventing abrasion, for example, a carbon film 5 having a thickness of about 10 nm is formed on the surface of the pad 2 and other sliders facing the recording medium.
In FIG. 1B, reference numeral 6 denotes a movable mirror having a function of inclining the optical path of the semiconductor laser light 8, and reference numeral 7 denotes an objective lens for condensing the semiconductor laser light 8 on the near-field light generating probe 3. The laser beam 8 is polarized in the plane of incidence on the probe, that is, in the direction perpendicular to the plane of FIG. 1B. The condensed semiconductor laser light 8 is converted into a small-sized near-field light 9 near the tip of the near-field light generating probe 3. The slider travels while flying above the recording medium substrate 10 by several tens of nm, and the near-field light 9 records and reproduces information 12 on and from the recording medium 11 formed on the substrate 10.

Next, the principle by which the probe 3 can generate near-field light with high efficiency will be described with reference to FIG.
Fig. 2 (a) shows the principle of surface plasma wave generation proposed by Kretschmann (Journal Physik, No. 2).
41, pages 313 to 324). In FIG. 2A, reference numeral 21 denotes an optically transparent prism, and reference numeral 22 denotes a metal thin film having a thickness of several tens nm, such as gold or silver. This prism has an incident angle q equal to or larger than the angle at which total reflection occurs at the bottom of the prism.
1, when a laser beam polarized (p-polarized) is incident on the plane of incidence, in the case of FIG. 2, parallel to the plane of the paper, the incident laser beam is normally totally reflected, but the incident angle is a specific angle. Is satisfied, the surface plasma wave 23 is excited at the interface between the metal and the air, and the power of the reflected light 24 decreases. The reflectance R at the bottom of the prism is represented by the following equation: the laser light wavelength is L, the dielectric constant of the optically transparent material constituting the prism at the laser light wavelength L is e1, and the dielectric constant of the metal thin film at the laser light wavelength L is the real number. Assuming that the part is e2, the imaginary part is e3, and the film thickness is d, it is almost expressed by (Equation 2).

[0020]

(Equation 2)

FIG. 2B shows a case where quartz is used for the prism and silver is used for the metal, the wavelength L of the incident light is changed, and the reflected light 24 is changed.
It is the result of having calculated the reflectance. For example, if the silver film thickness is 4
Assuming that the wavelength is 0 nm and the wavelength of the laser beam is 633 nm, when the incident angle q1 is 45.5 degrees, there is almost no reflected light, and it can be seen that the surface plasma wave is efficiently excited.

Using this principle, a surface plasma wave can be efficiently excited by the near-field light generating probe of the present invention. That is, in FIG. 3A, the incident angle of the laser beam 8 on the bottom surface of the quadrangular pyramid-shaped probe 3 is q, and the plane connecting the vertex of the quadrangular pyramid-shaped probe and the two vertexes of the bottom surface is opposite. The half angle of the vertex angle of a triangle in a plane parallel to the plane of incidence of the laser light is s1, the half angle of the vertex of the triangle in a plane perpendicular to the plane of incidence of the laser light is s2, the plane of incidence of the laser light and the quadrangular pyramid. Assuming that the half angle of the angle formed by the intersection line DEF of the slope is q2, these relationships are as shown in (Equation 3).

[0023]

(Equation 3)

FIG. 3B is a sectional view of the plane DEF of the probe 3 formed on the laser beam incident surface. In this case, the laser beam 8 is polarized (p-polarized) in a direction parallel to the sheet of paper, as in the case of FIG. The surface plasma wave 23 is excited and propagates in the direction of the edge E of the tetrahedral slope as shown in FIG. 3B in the cross section of FIG. 3B according to the Kretschmann principle. At this time, the incident angle q1 of the laser beam in FIG.
Corresponds to (90−q2) degrees in FIG. For example, the thickness of silver is 40 nm, and the wavelength of laser light is 633 n.
In the case of the example of m, since q1 = 45.5 degrees as described above, q2 is 44.5 degrees. s1, s2, and q are
It can be set arbitrarily so as to satisfy the relationship of (Equation 3).
For simplicity, the quadrangular pyramid has a regular tetrahedral shape (ie, s
1 = s2) and q = 0 (normal incidence), s
It is calculated using (Equation 3) that 1 = s2 = 44.5 (degrees).

However, in an actual probe, the dielectric constant e1 at the wavelength L of the laser light of the optically transparent substance constituting the probe and the dielectric constant e2 at the wavelength L of the laser light of the metal thin film in the actual probe. And the thickness d thereof, and the half angle s1 of the apex angle of the triangle in a plane parallel to the plane of incidence of the laser beam, and the half angle s2 of the apex angle of the triangle in a plane perpendicular to the plane of incidence of the laser beam for all values It is expected that a deviation from the design value will occur. For example, in the above example,
When s1 is larger than the design value by 1 degree and s1 = 45.5 degrees, q2 = 45.5 degrees and q1 = 44.5 degrees. When q1 = 44.5 degrees, as shown in FIG. 2B, the reflectance at the wavelength L = 633 (nm) increases to about 80%, and the surface plasma wave 23 is hardly excited.
To prevent this, according to (Equation 3), the incident angle q of the laser beam 8 on the bottom surface of the quadrangular pyramid-shaped probe 3 is changed from 0 degree to 1.degree.
What is necessary is just to increase to 93 degrees. This can be easily realized by changing the angle of the movable mirror 6. in this way,
In the near-field optical head of the present invention, even if various parameters deviate from the design values, the surface plasma wave can always be excited with high efficiency by adjusting the angle of the movable mirror.

The excited surface plasma wave propagates in the direction of the edge of the tetrahedral slope as shown in FIG. 3B and is collected at the edge. The surface plasma wave collected at the edge propagates along the edge toward the probe tip,
Finally collected at the probe tip. Surface plasma wave 2
3 attenuates as it propagates through the metal. In the case of a metal such as gold or silver, the distance over which the surface plasma wave 23 propagates without being attenuated is 1 to 3 μm. Therefore, the laser light 8
Needs to be condensed to a spot size of 1 μm or less using the objective lens 7 and converged near the tip of the probe.
Since the spot size is (laser beam wavelength) / (objective lens NA), for example, when a laser beam having a wavelength of 633 nm is used, the numerical aperture NA of the objective lens is desirably 0.6 or more.

As described above, the laser light is efficiently transmitted to the tip of the probe. At this time, near-field light is localized at an extremely large power density at the tip of the probe, and when the optical recording medium 11 is brought close to the probe 3, the near-field light propagates into the optical recording medium 11 with high efficiency. Recording and reproduction of information becomes possible. In a conventional near-field light generating probe using an optical fiber, light is absorbed by a metal film near the tip of the probe, and the light transmission efficiency is low. The probe in the near-field optical head according to the present invention uses the surface plasma wave 23 propagating on the surface of the metal film, so that its light transmission efficiency can be 10% or more.
It can be much larger. In addition, this light transmission efficiency is obtained by cutting a triangular prism-shaped glass, depositing a gold thin film on the surface thereof, bonding the glass piece on a prism, and irradiating one vertex of the triangular pyramid-shaped glass piece with laser light. It is larger than the conventional method of exciting a surface plasma wave. The reason is that, in the present invention, since the quadrangular pyramid shape is employed as the probe shape, all the light condensed at the probe apex can be efficiently used for exciting the near-field light as shown in FIG. As shown in (Equation 1) and (Equation 2), the material and structure of the probe are optimized to satisfy the conditions of Kretschmann, and the incident angle of the laser beam is changed by the movable mirror 6. , Provided a mechanism for correcting the manufacturing error of the probe,
The laser beam used to excite the near field is focused on a spot of 1 μm or less using a lens with a high NA to suppress the loss that occurs when a surface plasma wave propagates through a metal thin film. .

In this near-field optical head, for example, if an optical power of 10 mW is incident as an incident laser light power, an optical power of 1 mW or more, which is almost the same as that of a conventional practically used optical recording / reproducing apparatus, can be used. . A conventional near-field optical head using an optical fiber has a very low light use efficiency and an extremely low information transfer rate of 1 kbps. On the other hand, if the near-field optical head of the present invention is used, as described above, a signal of 1 mW or more, which is almost the same as that of the conventional optical recording / reproducing apparatus, can be obtained. Of about 10 MHz.

Next, the structure of the entire slider will be described. The height h of the probe 3 must always be smaller than the height h of the pad 2. As shown in FIG. 1B, the slider is only several tens of ns from the recording medium substrate 11.
m and run. The upper surface of the pad 2 corresponds to a sliding surface between the slider and the recording medium substrate 11. Therefore, when a situation occurs in which the slider comes into contact with the recording medium substrate during the recording / reproducing operation by the head, the upper surface of the pad comes into contact with the recording medium substrate. At this time, if the height h of the probe 3 is larger than the height h of the pad 2, the tip of the probe and the recording medium substrate come into contact with each other, causing wear of the probe. In order to prevent this, h must be always smaller than h. Not only must h be smaller than h, but also the difference between h and h must be very small. It is known that the intensity of the near-field light 9 does not greatly change at a distance from the probe tip up to the size of the probe tip, but sharply decreases as the distance from the probe tip further increases. The size of the tip of the probe in this embodiment is several tens to 100 nm, and if the distance between the probe and the medium becomes longer, the intensity of the near-field light 10 becomes extremely small on the recording medium 11. . The slider is several tens from the surface of the recording medium.
In order to travel while flying 0 nm, if the distance between the probe and the medium is increased by the size of the probe tip, that is,
In order to keep it at 0 nm or less, h and h need to be substantially the same, and the distance between the tip of the probe and the surface of the recording medium must be kept at about several tens nm when the slider is running. For this purpose, the difference between h and h must be controlled on the order of nm. This is a major point of the fabrication of the near-field optical head.

By using the near-field optical head in which the near-field generating probe is formed integrally with the slider as described above, a compact and lightweight device having the same performance as the head used in the conventional magnetic disk drive is provided. Thus, a near-field optical head having a simple configuration can be configured. In addition, since the slider is small and lightweight, the relative speed between the recording medium and the optical head for recording and reproducing information can be increased, and the information transfer speed can be improved.

FIG. 4 shows a second embodiment of the present invention using a cantilever. In FIG. 4, reference numeral 41 denotes a quadrangular pyramid-shaped probe formed at the tip of the cantilever 43, which is formed of an optically transparent material, for example, silicon dioxide or silicon nitride. On its surface, a metal thin film 42 for exciting and propagating a surface plasma wave 23 such as gold or silver is formed. Reference numeral 8 denotes a laser beam. The incident angle on the probe 41 is adjusted by the movable mirror 6, and the laser beam is condensed by the objective lens 7 near the tip of the probe 41. The dielectric constant of the material constituting the probe 41, the wavelength of the laser beam, the structure of the probe, and the like satisfy the relations of (Equation 1) and (Equation 2) as in the first embodiment, and the surface plasma wave is generated with high efficiency. Optimized to allow.

FIG. 5 shows a third embodiment of the present invention to which a contact type slider is applied. FIG. 5A is a perspective view of the near-field optical head of the present embodiment, and FIG. 5B is a cross-sectional view taken along the line FF of FIG. 5A.

In FIG. 5A, the slider 1 and the information recording medium 1 are placed on the slider 1 made of an optically transparent substance.
1 is provided with a pad 2 provided for controlling the contact state. In the embodiment of FIG. 1, three pads are provided on the bottom surface of the slider. In the present embodiment, only the pad 51 divided into four is provided. Pad 51
Is provided with a quadrangular pyramidal probe 3 for generating near-field light. The probe 3 is coated with a metal thin film 4 having a thickness of several tens nm as shown in FIG. A thin film for preventing abrasion, for example, a carbon film 5 having a thickness of about 10 nm is formed on the surface of the pad 51 and the other slider facing the recording medium. FIG.
(B) shows an example in which different materials are used as the metal thin film 4 and the wear preventing thin film 5, but both the wear resistance and the excitation characteristics of the surface plasma wave 23 described in the section of FIGS. It is also possible to cover the slider bottom surface and the probe surface with a material that satisfies the above conditions, for example, a chromium film. that way,
The fabrication process becomes easier. On the surface of the recording medium, a carbon film 52 for preventing wear is formed with a thickness of several nm, and a high molecular lubricant is also applied thereon with a thickness of several nm. The wear resistance of the recording medium 11 is improved by the carbon film and the lubricant. The slider 1 travels while contacting the recording medium substrate 10, and the recording and reproduction of information 12 on and from the recording medium 11 formed on the substrate 10 are performed by the near-field light 9.

FIG. 6 shows a fourth embodiment of the present invention using a flying slider. FIG. 6A is a perspective view of the near-field optical head of the present embodiment, and FIG. 6B is a cross-sectional view taken along a line GG of FIG. 6A.

In FIG. 6A, pads 61, 6 provided on the slider 1 made of an optically transparent material to control the flying state of the slider and the information recording medium 11 are shown.
2 are provided. In the present embodiment, 3
One pad is provided. A quadrangular pyramid-shaped probe 4 for generating near-field light adjacent to one of the pads 61
Is provided. In this embodiment, the height of the small pad 63 provided on the pad 61 is designed to be smaller than the height of the entire pad 61 and the pad 62 from the slider bottom surface. By doing so, the height from the slider bottom surface to the pad upper surface can be freely designed irrespective of the size of the probe 3. This allows
The flying height of the slider can be arbitrarily set. The height of the small pad 63 provided on the pad 61 is set slightly higher than the height of the probe 3 as in the first embodiment. Since the height of the small pad can be freely set according to the shape and size of the probe without considering the flying height of the slider, the degree of freedom in manufacturing the probe is increased.

FIG. 7 is a perspective view of an optical recording / reproducing apparatus to which the near-field optical head of the present invention is applied. The disk 71 composed of the recording medium substrate 10 and the recording medium film 11 is
2 and attached to a shaft 73 connected to a spindle motor fixed to the spindle motor. By this rotational movement, relative movement is performed with respect to the slider 1 on which the near-field optical head shown in FIG. 1 or any of FIGS. 5 to 6 is mounted. An actuator 74 for positioning the slider 1 is also fixed to the base 72, and an arm 76 and a suspension 77 are attached to a movable portion 75 thereof. The movable portion 75 rotates around its central axis, and moves the slider 1 attached to the tip of the suspension 77 in the radial direction of the disk 71. Further, when a disk with a small tracking pitch is used, an actuator 78 that allows finer positioning than the actuator 74 is attached to the tip of the arm 76. A connector 80 is connected to an interface 79 fixed to the base 72, and power is supplied to drive the apparatus through a cable connected to the connector 80, a recording / reproducing command to the apparatus, input of recording information, reproduction information Output. Supply of laser light to the near-field optical head, and detection of recorded information,
The detection of the displacement information of the slider from the track and the detection of the displacement between the objective lens and the slider are described in detail in FIG.
As will be described below, this is performed using the optical head 81 fixed to the base. Immediately below the slider, a movable mirror 6, an objective lens 7, and a movable portion 82 on which an actuator for moving the objective lens 7 are mounted are provided. FIG.
Although not explicitly described, the movable portion 82 is moved following the slider 1 in the radial direction of the disk 71 by an actuator that moves the entire movable portion.

Next, the operation of the optical head 81 and the movable portion 82 will be described in detail with reference to FIG. The laser beam 8 generated by the semiconductor laser 83 is changed into a parallel beam by the collimator lens 84, passes through the beam splitter 85, and is changed in direction by the movable mirror 6. Laser beam 8 whose direction has been changed by movable mirror 6
Is condensed on the probe 3 by the objective lens 7 to generate near-field light, and recording and reproduction on a recording medium formed on the disk 71 are performed. The laser beam 8 whose intensity has been modulated by the information on the recording medium passes through the objective lens 7, is redirected by the movable mirror 6, is reflected by the beam splitter 85, and is guided to the detection system. The detection system detects a read signal, detects a displacement of the focus of the laser beam condensed by the objective lens 7 in the optical axis direction of the probe 3, and detects a displacement in a direction perpendicular to the optical axis. The displacement between the laser beam focal point and the probe 3 in the direction perpendicular to the optical axis is focused by a lens 86 and the laser beam split by a beam splitter 87 is focused only in one direction by a lens, for example, a cylindrical lens 88. The light is condensed on the split photodetector 89, and the focusing is performed using a focus error detection method called an astigmatism method. The detection of the deviation between the focal point of the laser beam and the optical axis of the probe 4 in the vertical direction is performed by the 4-split photodetector 90 as follows. When the focus of the laser beam is displaced in the radial direction between the probe 3 and the disk 71, the sum signal of the detectors A and C of the four-split photodetector and the sum signal of the detectors B and D are unbalanced. Occurs. Therefore, the position shift can be detected by using the difference between these sum signals. On the other hand, the focus of the laser light is
Is shifted in the circumferential direction of the disk 71,
An unbalance occurs between the sum signal of the detector A and the detector B of 0 and the sum signal of the detector C and the detector D. Therefore, the position shift can be detected by using the difference between these sum signals. Using these displacement signals, for example, the two-dimensional actuator 91 attached around the objective lens can be used to detect the displacement of the focus of the laser beam from the probe 3 in the optical axis direction and the displacement of the disk 71 in the circumferential direction. The focus of the objective lens is always adjusted to the probe 3 by correcting the displacement of the focus of the laser beam and the radial position of the disk 71 of the probe 3 by the actuator 92 for moving the entire portion 82, and the near-field light is efficiently generated. I can do it. Lastly, in the case of using a so-called phase-change type recording medium or a read-only concave-convex recording medium as a recording medium formed on a disc, for example, the reproduction of the recorded information is performed by two quadrant detectors 89 and 90. This is performed using the sum signal intensities of all the detectors.

Next, the positioning and servo technology according to the present invention will be described with reference to FIG. In FIG. 9, 93
To 98 show seven of the many information tracks provided on the disk. Reference numeral 99 denotes a group of address marks for identifying a track number, which differs for each track, and detects on which track the probe 3 is located by using this mark. Each track is provided with a wobble mark 100 and a clock mark 101. At the time of recording and reproducing information, the probe 3
Move up from the bottom of the figure. The probe 4 passes over the wobble mark 100 after the clock is created through the clock mark 101. If the position of the probe deviates from the center of the track, signals from two consecutive wobble marks become unbalanced, and the difference between these signals is taken as a tracking error signal. The actuator 74 (and the actuator 78 if attached) is driven in accordance with the error signal, and the probe 3 is positioned at the center of the track. The objective lens 7 operates so that the focal point of the laser beam is always positioned on the probe 3 as described above, so that the focal point of the laser beam is also servoed following the above servo operation. Probe 3 has wobble mark 1
After passing over 00, it passes over the address mark 99, enters the recording unit 102 for recording information, and records and reproduces information.

Next, a seek operation for moving the probe 3 to a target track will be described. In the seek operation, the system controller compares the position where information designated by an external control device is to be recorded and reproduced with the actual position of the probe 3 detected by the four-split photodetectors 90 and 91. Based on this comparison result, the positioning actuator 74 (and the actuator 78 if attached) is driven to position the probe 3 at a predetermined track on the disk. At this time, the objective lens 7
The focus position of the laser beam and the position of the probe 3 are set in the optical axis direction,
And while being servo-controlled by the actuator 91 so as not to be displaced in the plane perpendicular to the optical axis and in the circumferential direction of the disk,
A slider 1 on which a probe is mounted is moved by an actuator 92 for moving the entire movable portion 82 in the radial direction of the disk.
Is moved to follow. Slider 1 and movable part 8
2 is extremely lightweight, so that the time required for seeking can be reduced to the same level as a normal magnetic disk drive.

Finally, the recording medium used in the present invention will be described. In the present invention, a laser beam is focused on a near-field light generating probe covered with a metal thin film, a surface plasma wave propagating in the metal thin film is excited, and the energy is concentrated as a localized plasma wave at the probe tip. The localized plasma wave at the tip of the probe interacts with the near-field of the medium and is modulated by changes in the refractive index, absorption rate, and shape recorded in the medium. This modulated signal is reflected in a change in the intensity of the reflected light from the probe, and information is finally reproduced by the photodetector. Therefore, as the information medium, an information medium having a large interaction with the plasma wave localized at the tip of the probe, for example, a fine metal dot formed on a substrate is suitable. The size of the metal dot is approximately the same as the radius of curvature of the probe tip (approximately 2
In the case of 0-100 nm), particularly large modulation of the amount of reflected light from the probe is observed. Further, a medium in which irregularities are provided on the medium substrate itself and a metal thin film is formed thereon is also suitable as the information medium used in the present invention. This is because the dielectric constant felt by the localized plasma wave is greatly modulated at the edge portion of the concavo-convex bit, and as a result, a large modulation of the probe reflected light amount is obtained. The above is an example of a read-only medium. However, as an example of a recordable medium, a phase change medium using a phase change between a crystalline state and an amorphous state is suitable. This is because, in a phase change medium, information is recorded in the medium in the form of a change in the refractive index or absorption rate recorded in the medium. Furthermore, when a metal thin film is formed on the surface of the phase change medium, surface plasma waves are intensively excited in the metal film immediately below the probe, and recording and reproduction with higher efficiency can be performed.

[0041]

As described above, according to the present invention, a near-field optical head equipped with a near-field light generating probe having high near-field light generating efficiency and an additional method for detecting the distance between the recording medium and the optical head are provided. It is possible to provide a near-field optical head and an optical recording / reproducing apparatus using the same, which are compact, lightweight, and have a simple configuration, and do not require special equipment. The information transfer speed of the playback device
It can be dramatically increased.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing an embodiment of a first near-field optical head of the present invention using a slider, wherein FIG. 1A is a perspective view and FIG.

FIGS. 2A and 2B are diagrams illustrating the principle of excitation of surface plasma waves used in the near-field optical head, wherein FIG.
FIG. 4 is a diagram showing a calculation result of reflectance.

3A and 3B are views for explaining a method of exciting a surface plasma wave in the near-field optical head of the present invention, wherein FIG. 3A is a perspective view and FIG.

FIG. 4 is a diagram showing a second embodiment of the near-field optical head of the present invention using a cantilever.

FIG. 5 is a diagram showing a third embodiment of the present invention using a contact type slider. (a) is a perspective view, (b) is a sectional view.

FIG. 6 is a diagram showing a fourth embodiment of the present invention using a slider. (a) is a perspective view, (b) is a sectional view.

FIG. 7 is a perspective view of an optical recording / reproducing apparatus to which the near-field optical head of the present invention is applied.

FIG. 8 is a diagram showing details of an optical head unit used in FIG. 7;

FIG. 9 is a view for explaining a servo operation in the optical recording / reproducing apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Slider, 2 ... Pad, 3 ... Probe, 4 ... Metal thin film, 5 ... Thin film for wear prevention, 6 ... Movable mirror, 7 ... Objective lens, 8 ... Semiconductor laser light, 9 ... Near-field light, 10 ... Substrate Reference numeral 11: Recording medium, 12: Recording information, 21: Prism, 22: Metal thin film, 23: Surface plasma wave, 41: Probe, 42: Metal thin film, 43: Cantilever, 51: Pad, 52: Protective film, 61 ... Pad, 62: Pad, 63: Small pad, 71: Disk, 72: Base, 73: Shaft, 74: Actuator, 75: Moving part, 76: Arm, 77: Suspension, 78: Actuator, 79: Interface, 80: Connector, 81: Optical head, 82: Optical head movable part, 83: Semiconductor laser, 84: Collimating lens, 85: Beam split 86, a lens, 87, a beam splitter, 88, a cylindrical lens, 89, a 4-split photodetector, 90, a 4-split photodetector, 91, a two-dimensional actuator, 92, an actuator, 93, 94, 95, 96 , 97, 98: information track, 99: clock mark, 100: wobble mark, 101: address mark, 102: information recording section.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Mitori Kato 2520 Akanuma-cho, Hatoyama-cho, Hiki-gun, Saitama Prefecture Within Hitachi, Ltd. F-term in Hitachi Basic Research Laboratory (reference) 5D119 AA10 AA24 AA43 CA03 CA06 DA01 DA05 FA02 JB03 LB05

Claims (19)

[Claims] A probe for generating a near-field light having a minute spot size on the information recording medium while making a relative movement while contacting the information recording medium or floating at a substantially constant interval; A laser light source that provides irradiation light for generating near-field light to the probe, and a near-field light head including a unit that condenses the laser light onto the probe, wherein the probe has a quadrangular pyramid shape,
A near-field optical head, wherein a material constituting the probe is formed of an optically transparent substance, and the entire surface of the probe is covered with a metal film. 2. The near-field optical head according to claim 1, wherein
A near-field optical head, wherein a polarization direction of the laser light is parallel to a plane connecting two apexes of the cone-shaped probe and a quadrangular bottom face. 3. The near-field optical head according to claim 1, further comprising a mechanism for adjusting an incident angle of the laser light on a bottom surface of the quadrangular pyramid-shaped probe. Light head. 4. The near-field optical head according to claim 1, wherein a wavelength L of the laser light, a dielectric constant e1 of the optically transparent material forming the probe at the wavelength L of the laser light, Real part e2 and imaginary part e3 of the permittivity of the metal film covering the entire probe surface at the wavelength L of the laser light.
And the thickness d, the incident angle q of the laser light on the bottom surface of the quadrangular pyramid-shaped probe, the half angle of the apex angle of a triangle in a plane parallel to the incident surface of the laser light, s1, A near-field optical head, wherein a half angle of a vertex angle of a triangle in a plane perpendicular to a light incident surface s2 substantially satisfies (Equation 1). (Equation 1) 5. The near-field optical head according to claim 1, wherein the metal covering the probe surface is any one of gold, silver, chromium, and aluminum. 6. A near-field optical head according to claim 1, wherein said means for converging said laser beam onto said probe is a condensing lens, and has a numerical aperture of at least 0.6 or more. And near-field light head. 7. The near-field optical head according to claim 1, wherein a spot diameter of the laser beam focused on the probe is at least 1 μm or less. 8. An optically transparent near-field optical head according to claim 1, wherein said probe makes a relative movement while being in contact with an information recording medium or floating at a substantially constant interval. A near-field optical head formed on a slider. 9. The near-field optical head according to claim 8,
On the slider, a columnar pad provided for controlling the contact or floating state of the information recording medium, and a cone-shaped probe for generating near-field light of a minute spot size are provided in close proximity. A near-field optical head, comprising: 10. The near-field optical head according to claim 1, wherein the probe is a cantilever in which an optically transparent probe is covered with a metal film. Light head. 11. A near-field optical head according to claim 1, further comprising: an optical recording medium; and light receiving means for detecting a modulation signal of the near-field light generated by the near-field optical head by the recording medium. An optical recording / reproducing apparatus characterized by the above-mentioned. 12. The optical recording / reproducing apparatus according to claim 11, wherein a modulation signal of the near-field light by the recording medium is reflected light from the probe. 13. An optical recording / reproducing apparatus according to claim 11, wherein said means for converging illumination light to said probe, and a shift between a focus position of said illumination light condensed by said light condensing means and a probe position. An optical recording / reproducing apparatus comprising: means for detecting; and a movable mechanism for correcting a relative position between the light condensing means and the probe. 14. The optical recording / reproducing apparatus according to claim 13, wherein said condensing means and a movable mechanism for correcting a relative position between said condensing means and said probe constitute another optical information recording / reproducing apparatus. An optical recording / reproducing apparatus, wherein the optical recording / reproducing apparatus is mounted on a movable mechanism which is separated from an element and allows the light collecting means to access a predetermined position on a recording medium. 15. An optical recording / reproducing apparatus according to claim 11, wherein information recorded on said optical recording medium is formed by metal dots. 16. An optical recording / reproducing apparatus according to claim 11, wherein information recorded on said optical recording medium is formed by irregularities on a medium substrate, and the surface thereof is covered with a metal thin film. Optical recording and reproducing device. 17. An optical recording / reproducing apparatus according to claim 11, wherein information recorded on said optical recording medium is recorded by modulating a refractive index or an absorptivity of a medium material. Recording and playback device. 18. An optical recording / reproducing apparatus according to claim 17, wherein the surface of said optical recording medium is covered with a metal thin film. 19. An optically transparent slider that moves relative to an information recording medium, and a surface that is provided on a surface of the slider that faces the information recording medium and generates near-field light having a minute spot size. A near-field optical head comprising: a quadrangular pyramid-shaped probe covered with a metal thin film; and a pad for controlling a contact or a floating state of the information recording medium.