JP2000173093A - Optical element and information recording and reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute an optical element and an information recording and reproducing apparatus in which information can be transferred at high speed and in which a recording operation can be performed with a higher density than an optical disk apparatus in conventional cases by a method wherein a pinhole which has a sufficient light transmittance is formed in a slider. SOLUTION: The end face of an optical waveguide or an optical fiber 4 is cut obliquely. A metal film 5 is formed on the end face. A pinhole 6 is formed in the metal film 5. The angle which is formed by the optical axis of the optical waveguide or the optical fiber 4 with the end face is set at an angle at which a surface plasmon is excitated in the metal film. Thereby, the transmitted light rate of the pinhole 6 can be increased, and it is possible to constitute an information recording and reproducing apparatus in which a recording operation can be performed with high density and whose data transfer rate is fast.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element and an information recording / reproducing apparatus, and more particularly to an optical element for irradiating a specific area of space with light and information for optically recording / reproducing information on / from an information recording medium. The present invention relates to a recording / reproducing device.

[0002]

2. Description of the Related Art When light is focused by a lens, it is difficult to focus light in a region smaller than the wavelength. Use a pinhole in an opaque substance as a means of selectively irradiating light to a region smaller than the wavelength, and use this to construct a microscope with a resolution higher than that of a conventional optical microscope Is described in the Journal of the Japan Society of Applied Physics, “Applied Physics,” Vol. 65, No. 1.

[0003] In addition, regarding the application of the present invention to an information recording / reproducing apparatus, see the journal “Applied Physics L”.
61, No. 2, page 143, reports Betzig et al. in the journal "Japanes."
e Journal of Applied Physi
cs "on page 443 of Vol.
Etc. are described.

As an invention in which this is applied to an information recording / reproducing apparatus, Japanese Patent Application Laid-Open No. 3-171434 has been filed. JP-A-3-171434 describes that a medium for recording information is rotated at a high speed, and a light source, a lens,
Place a slider containing pinholes, fly head,
Alternatively, the invention using a negative pressure head is described. Also in this case, by making the size of the pinhole smaller than the wavelength of light, the recording mark on the medium can be made smaller than that of a normal optical disc, and the recording density can be made higher than that of a normal optical disc. Can be.

[0005]

In an information recording / reproducing apparatus, a signal intensity of a certain intensity is required in order to increase a transfer rate of information. It has been reported as described above that information is recorded and reproduced using light that has passed through a fine pinhole, but the light transmission efficiency of the pinhole is generally about 10 −4 to −5. It is.

When a normal semiconductor laser is used as a light source, the output is about several tens of mW, and when the transmission efficiency has the above value, the intensity of light applied to a recording medium for recording and reproducing information becomes Generally, it becomes 0.1 to 1 μW.

When information is reproduced, for example, with light of this intensity, it is difficult to obtain a sufficient SN ratio, as will be described later. It is possible to improve the S / N ratio by narrowing the frequency band of the signal, but in this case, the information transfer rate is significantly reduced as compared with a normal magnetic disk device or optical disk device.

In order to increase the information transfer speed, it is necessary to further increase the relative speed between the information recording medium and the means for recording and reproducing information. Further, in an information recording / reproducing apparatus using a pinhole, it is necessary to keep a constant distance between the pinhole and the information recording medium.

As a method satisfying these requirements, a method of mounting a pinhole on a flying slider is a useful method. However, in the configuration described in JP-A-3-171434, not only a pinhole but also a laser light source and a lens are mounted on a flying slider.

When the apparatus is actually constructed, if a laser light source or a lens is mounted on the slider, the mass of the slider increases. Then, the following characteristic of the recording medium is deteriorated, and it is actually difficult to construct the apparatus.

The above-mentioned Japanese Patent Application Laid-Open No. 3-171434 does not disclose a specific pinhole structure.
Assuming that the structure of the pinhole is similar to that reported by Betzig et al., Hosaka et al., As described above, the amount of signal light is reduced.

An object of the present invention is to provide an optical element capable of transferring information at a high speed by mounting a pinhole having a sufficient transmissivity on a slider and recording at a higher density than a conventional optical disk device. And an information recording / reproducing apparatus.

[0013]

In the prior art, light is condensed by a lens or a pinhole is provided at the tip of an optical fiber.
Light was incident from the opposite end face of the optical fiber to irradiate the pinhole with light. Since recording / reproducing is performed at a higher density than a conventional optical disk device using light passing through a pinhole, the size of the pinhole needs to be smaller than the wavelength of light emitted from the light source.

When the light is focused by a lens, the focused spot is
In principle, it cannot be smaller than the wavelength of light.
Further, in an optical fiber, light is confined in a core, but the light spreads to about its wavelength. Therefore, the light passing through the pinhole becomes very small with respect to the light applied to the pinhole,
Efficiency decreases.

In the present invention, when irradiating light to a pinhole, light that spreads to about the wavelength of light and does not directly hit the pinhole is guided to the pinhole to improve efficiency. In order to guide light to the pinhole, the present invention utilizes surface plasmons. When P-polarized light is incident on a metal thin film at a certain incident angle, part of the incident light changes to surface plasmon. By reflecting the surface plasmon on the edge of the metal thin film and collecting the surface plasmon on the pinhole, light not directly hitting the pinhole can be guided to the pinhole.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. A first example of the embodiment of the present invention will be described with reference to FIGS. 1 is a cross-sectional view of a slider on which the optical element of the present invention is mounted, FIG. 2 is an enlarged view of the vicinity of the pinhole 6 in FIG. 1, FIG. 3 is an explanatory view of the operation principle of the present invention, and FIG. FIG. 5 is an enlarged view of the vicinity of an arm in FIG. 4, and FIG. 6 is an enlarged view of an information recording medium of the information recording and reproducing apparatus in FIG.

The slider 1 shown in FIG. 1 moves relative to the information recording medium 2 at a relative speed v. The slider 1 is supported by an arm 3 and is pressed against the information recording medium 2 with a constant force. An air flow is generated due to the relative movement between the slider 1 and the information recording medium 2, and the fluid force generated by the air flow acts in a direction to separate the slider 1 from the information recording medium 2. The slider 1 floats on the information recording medium 2 at a position where the pressing force of the arm 3 and the fluid force are balanced with a certain interval.

An optical fiber 4 is fixed to the slider 1. Although not clearly shown in FIG. 1, light is incident on the optical fiber 4 from a light source outside the slider described later. On the surface of the slider 1 facing the information recording medium 2,
An end face of the optical fiber 4 appears, and a metal film 5
Is formed. The light incident on the optical fiber 4 passes through a pinhole 6 provided in the metal film 5 and irradiates the information recording medium 2.

The transmitted light of this light is detected by the photodetector 14. The photodetector 14 includes a lens 11, a Wollaston prism 12, a photodiode 13, and the like. The transmitted light is condensed by a lens 11, further polarized and separated by a Wollaston prism 12, and each polarized component is separately converted into an electric signal by a photodiode 13.

The information recording medium 2 comprises a transparent substrate 10 and a recording film 9. As a material of the transparent substrate 10, quartz, polycarbonate, or the like can be used.
The recording film 9 is made of Pt-C used for a magneto-optical disk drive.
It is an o-type magneto-optical recording film.

A certain mark is formed on the recording film 9 by removing a part of the recording film 9 by an etching process or changing the direction of magnetization, and information is recorded by the mark. . For example, when a part of the recording film 9 has been removed, the light transmittance of the removed part is higher than that of the other part. Therefore, the information recorded on the recording film 9 can be read out by irradiating the recording film 9 with light and detecting the intensity of the transmitted light.

As will be described later, linearly polarized light enters the optical fiber 4, and linearly polarized light passes through the pinhole 6. Information is also recorded on the recording film 9 according to the direction of magnetization. When linearly polarized light enters, the polarization direction is rotated by the Faraday effect. Rotation of the polarization direction can be detected by separating the transmitted light by polarization using the Wollaston prism 12 and separating and detecting two polarized components by the photodiode 13. As a result, information can be reproduced.

The slider 1 is further provided with a coil 7 for irradiating the recording film 9 with pulsed light from the pinhole 6 and, at the same time, pulsing from the cable 8 to the coil 7 in accordance with the information to be recorded. Information can be recorded by supplying a current that reverses the sign.

Although not clearly shown in FIG. 1, a few nm thick C film is further formed on the surface of the recording film 9, and a high molecular lubricant is further coated thereon by several nm. ing.
The C film and the lubricant enhance the wear resistance of the recording film 9.

FIG. 2 is an enlarged view of the vicinity of the pinhole 6, wherein FIG. 2A is a longitudinal sectional view and FIG. 2B is a transverse sectional view. The optical fiber 4 shown in FIG. 1 includes the core 15 and the clad 16 shown in FIG. The normal to the end face of the optical fiber 4 is inclined by an angle θ with respect to the optical axis (center) of the optical fiber 4.

Further, the end face of the optical fiber 4 is subjected to etching, and the core 15 is recessed with respect to the clad 16. Such processing can be performed by using a silica-based optical fiber as the optical fiber and etching the end face of the optical fiber with, for example, 50% hydrofluoric acid at room temperature for about 10 seconds.

On this, a metal film 5 is formed. Ag or Au can be used as the material of the metal film 5. When the optical fiber 4 is a silica-based optical fiber,
Since Ag and Au do not adhere well, it is preferable to provide a Cr underlayer of about several nm. The thickness of the metal film 5 will be described later.
A pinhole 6 is provided in the metal film 5. This pinhole 6 can be processed using, for example, a focused ion beam.

As shown in FIG. 2, the direction of polarization of the light propagating in the optical fiber 4 and incident on the end face is in the plane where the optical axis of the optical fiber 4 and the normal line of the end face of the optical fiber 4 meet. is there.
That is, P-polarized light is applied to the metal film 5. Therefore, when the incident angle with respect to the metal film 5 satisfies a certain condition, surface plasmons having a mode as shown in FIG. 2 can be excited at the interface between the metal film 5 and the outer space.

For example, if the material of the metal film 5 is Ag and the wavelength λ of the incident light in vacuum is 630 nm, the refractive index n of the metal film 5 is 0.065-4.0i. In FIG. 1, the space between the metal film 5 and the information recording medium 2 is air,
Its refractive index is about 1.0. Then, the propagation constant k of the surface plasmon excited on the surface of the metal film 5 is given by Expression 1 where the propagation constant of the incident light is k0 = 2π / λ.

[0030]

(Equation 1)

Generally, light confined in the core of an optical fiber is weak, so that light propagating in the core can be approximately considered as a plane wave. Therefore, the refractive index of the core 15 is n
In the case of f, when the angle θ between the normal to the end face of the optical fiber 4 and the optical axis (center) of the optical fiber 4 satisfies Equation 2, surface plasmon is excited.

[0032]

(Equation 2)

As described above, the material of the metal film 5 is Ag,
Assuming that the refractive index nf of the core 15 is 1.457, the surface plasmon can be excited at an angle θ of about 45.1 degrees. This method is known as Kretschmann.
Surface plasmon is excited by the arrangement. Angle θ
Is 46.2 degrees for Au and 43.9 degrees for Al, for example, in addition to Ag.

The cross section of the core 15 with respect to the plane perpendicular to the optical axis of the optical fiber 4 is circular, and the end face of the optical fiber 4 on which the metal film 5 is formed is positioned with respect to the optical axis of the optical fiber 4. As shown in FIG. 2, the cross-sectional shape is elliptical. Assuming that the diameter of the core 15 is D, the core 1
The shape of the end face of No. 5 is such that the length of the short axis is D and the length of the long axis is D
/ sin θ.

For example, if the diameter D of the core 15 is 3 μm, the length of the major axis is about 4.2 μm. Therefore, the metal film 5 is irradiated with light in a range of about 4.2 μm. The excited surface plasmon, as shown in FIG.
In the direction of the major axis of the ellipse, it propagates in a positive direction with respect to the x-axis in FIG.

Here, consider the case where the angle θ deviates from the above-mentioned value. The condition for exciting the surface plasmon is obtained from the condition that the surface plasmon causes phase matching with the incident light. Therefore, when the angle θ is shifted, the phase matching is shifted.

Here, the condition that the phase of the surface plasmon generated at both ends of the major axis of the ellipse is shifted by 360 degrees gives an indication of the phase shift and gives an indication of the allowable value of the angle shift. When this condition is rewritten, Equation 3 is obtained.

[0038]

(Equation 3)

When this is rewritten using the relationship of Expression 1 (k0 = 2π / λ), the following Expression 4 is obtained.

[0040]

(Equation 4)

That is, if the angle between the normal to the end face of the optical fiber 4 and the optical axis (center) of the optical fiber 4 is between the two angles given by the equation 4, the surface plasmon is excited. It is thought to be done.

The material of the metal film 5 is Ag, and the diameter D of the core 15 is
Is 3 μm, when the angle θ is about 38.3 degrees in the smaller one and 55.9 degrees in the larger one, the phase of the surface plasmon generated at both ends of the major axis of the ellipse becomes 36 degrees.
It will be shifted by 0 degrees. Therefore, when the angle θ is between 38.3 degrees and 55.9 degrees, it can be considered that surface plasmon excitation occurs.

From Equations 3 and 4, the smaller the diameter D of the core 15 is, the wider the angle at which surface plasmon excitation occurs becomes. However, the diameter D of the core 15 is generally smaller than the wavelength λ of the incident light in vacuum. In such a case, the confinement in the core 15 becomes weak, and the incident light spreads to about the wavelength λ. Therefore, it is meaningless if the diameter D of the core 15 is smaller than the wavelength of the incident light.

When the diameter D of the core 15 increases,
Since the angle range in which surface plasmon excitation occurs is narrowed, the range of the diameter D of the core 15 is about the same as the wavelength λ to about 10 times. For example, when the wavelength λ is 630 nm, the range of the diameter D of the core 15 may be approximately 600 nm to 6 μm. This coincides with the core diameter of a normal communication optical fiber.

However, considering the adhesion strength of the metal film 5 to the core 15 and the abrasion resistance to the information recording medium 2, it is effective to use the metal film 5 as a multilayer film made of different metals. For example, in order to improve the abrasion resistance by forming an Ag film on a Cr film as a base film,
It is also effective to form a Cr film thereon. In this case, the propagation constant k of the surface plasmon cannot be given by a simple equation such as Equation 1. In this case, it is necessary to determine the range of the angle θ by Expression 3.

Regarding the thickness of the metal film 5, if it is too thin,
The influence of the interface between the metal film 5 and the core 15 appears, and the above-mentioned analysis does not hold. However, if the angle θ is selected in consideration of the influence of the interface, the same operation can be expected. If it is too thick, the light that has propagated through the core 15 will be absorbed by the metal film 15,
Light does not reach the interface between the metal film 15 and the space.

The imaginary part of the refractive index of a typical metal is about 2 to 10 depending on what is selected as the material of the metal film 15. Therefore, for example, considering the thickness at which the amplitude of light is approximately 1 / e at the interface between the metal film 15 and the space, when the wavelength of the incident light is, for example, 630 nm, about 10
nm to 50 nm. The thickness of the metal film 15 is desirably set to this level.

As described above, there is a step between the end faces of the core 15 and the clad 16, and a step is also formed on the metal film 5 formed thereon, thereby forming an elliptical edge. The surface plasmon excited at the interface between the metal film 5 and the space propagates in the positive direction of the x-axis in FIG. 2 and is reflected at this edge. Core 1
The ellipse, which is the end face of No. 5, is near the point A in FIG.
It can be approximated by a parabola shown by

[0049]

(Equation 5)

The focus of the parabola in Equation 5 is from point A to (D ·
sin θ) / 2. The reflected surface plasmons are collected at this focal point. Pinhole 6
It is provided at the position of this focal point, and L in FIG.
(D · sin θ) / 2. Surface plasmons propagating toward the pinhole 6 are scattered at the edge 17 of the pinhole 6. The size of the pinhole 6 is smaller than the wavelength of light incident on the optical fiber 4.

For example, if the angle θ in FIG.
Light transmitted through pinhole 6 and edge 1 of pinhole 6
The light scattered by 7 is only the light that propagates in the core 15 and directly enters.

Up to now, the Journal of the Japan Society of Applied Physics, “Applied Physics,” Vol. 65, No. 1, and the journal “Applied”
61, N of Physics Letter
o.2, page 143, the journal "Japanese J
own of Applied Physic
35, p. 443, the proportion of the light scattered by the edge 17 of the pinhole 6 and irradiated on the information recording medium 2 among the light propagating in the core 15 is as follows: It is 10 minus 5th power to minus 4th power.

Assuming that the intensity of the incident light is several tens mW, which is the output of a normal semiconductor laser, the light applied to the information recording medium 2 is 0.1 to 1 μW, which is extremely weak. The S / N ratio of the reproduced signal varies depending on the frequency band of the signal. However, the reproduction of a digital signal usually requires an S / N ratio of about 20 dB for the frequency band corresponding to the information transfer rate. Is done.

When the Faraday rotation angle in the recording film 9 is, for example, 1 °, the output for 1 μW input is 3
It is about 5 nW. The wavelength of the light source is 630 nm, the quantum efficiency of the photodiode 13 is 100%, and the magnitude of a resistor for converting the current output of the photodiode 13 into a voltage is 10 k.
Assuming that the temperature of the apparatus is 300K in absolute temperature and the transmittance of the recording film 9 is 10%, even if only shot noise and thermal noise which cannot be avoided in principle are considered, S
The frequency band where the / N ratio is 20 dB is about 20 kHz. That is, the transfer rate of information is limited to about 20 kb / s, and the transfer rate is significantly lower than that of a normal magnetic disk device or optical disk device.

When the angle θ is selected to be an angle at which the surface plasmon is excited, the excited surface plasmon is incident on the edge 17 of the pinhole in addition to the directly incident light. As described above, when the pinhole 6 is provided at a position where surface plasmons are collected, more light is incident on the edge 17, and the pinhole 6 has a smaller angle θ than when the angle θ is 0. A very bright point light source.

For example, if the angle θ is selected to be an angle at which the surface plasmon is excited, and the intensity of the light emitted from the pinhole 6 to the information recording medium 2 becomes ten times the above-mentioned value, it is avoided in principle. If only shot noise and thermal noise that cannot be considered are considered, the frequency band where the S / N ratio is 20 dB is about 1.6 MHz, and a transfer rate of about 1.6 Mb / s is possible in principle. Similarly, when the magnification becomes 100 times, the information recording medium 2 is irradiated with 100 μW light, and the transfer rate can be 100 Mb / s in principle.

In the first example of this embodiment, a pinhole 6 is provided on the end face of the optical fiber. It is possible to form a similar optical system with a bulk optical system. For example, if the information recording medium 2 has undulation, the slider 1
Is displaced following this. Then, the relative position between the optical system that causes light to enter the slider 1 and the slider 1 changes,
The angle of incidence on the pinhole changes. The first
In the example, the angle θ is fixed when the optical fiber 4 is processed, and does not change from this angle. Therefore, stable performance can be obtained.

FIG. 3 is an explanatory view of the operation principle of the present invention, and is also an enlarged view of the vicinity of the pinhole 6. In the first example, the light passing through the pinhole 6 and the edge 17
The recording film 9 is illuminated with the light scattered by the above to record and reproduce information. In order to record and reproduce information optically,
The size of the light spot needs to be smaller than or larger than the recording mark. It is difficult to record and reproduce a recording mark much smaller than the light spot.

In an ordinary optical disk device, light is collected by a lens in order to form a light spot. In this case, it is theoretically difficult to obtain a spot smaller than the wavelength of light. In a normal optical disk device, the wavelength of the light source is approximately 6
The spot size is about 00 to 800 nm, and the spot size is also about this level. On the other hand, in the first example, the size of the light spot is set to the size d of the pinhole 6 and the size of the metal film 5 is set.
This value is the sum of the depth of light penetration into the light.

When the processing of the pinhole 6 is performed by a typical FIB apparatus, the diameter d of the pinhole 6 is several tens nm.
Since the depth of light penetration is also typically several tens of nm, the size of the light spot is 100 nm.
It is as follows. Therefore, it is possible to record and reproduce smaller recording marks than in the case of a normal optical disk device. Thus, an information recording / reproducing device having a higher recording density than a normal optical disk device can be configured.

In FIG. 3, when the distance h between the pinhole 6 and the recording film 9 is 0, the size D of the light spot on the recording film 9 is changed to the size d of the pinhole 6 by a metal as described above. This is a value obtained by adding the depth of light penetration into the film 5. But,
When the interval h increases, the light spreads due to diffraction, and the size D of the light spot increases. In order to consider the limit of the interval h, a two-dimensional Fourier transform is performed on the amplitude of light on the recording film 9. Then, in order to create a light spot of size D, the wave vector p on the recording film 9
Generally requires a spatial frequency component represented by Expression 6.

[0062]

(Equation 6)

Here, since it is considered that a light spot sufficiently smaller than the wavelength of the light incident on the optical fiber 4 is formed by using the pinhole 6, the wavelength of the light incident on the optical fiber 4 is set as λ. , D <λ. Pinhole 6
The absolute value of the in-plane spatial frequency of the recording film 9 is π /
Consider a component that is D.

Hereinafter, this component is referred to as a. Since the amplitude of light on the recording film 9 satisfies the Helmholtz equation, D <
Equation 7 shows how λ and a depend on the distance z from the pinhole 6. Here, Equation 8 is obtained by using C as a proportional constant.

[0065]

(Equation 7)

[0066]

(Equation 8)

From equation (7), it can be seen that a rapidly decreases in the region where z> 1 / γ. Therefore, the interval h
Must be less than 1 / γ. As described above, the size D of the light spot needs to be at most the same as the size l of the recording mark.

Here, assuming that the wavelength λ is 630 nm and the light spot size D is 100 nm, 1 / γ ≒ 34n
m. That is, in order to record and reproduce a recording mark having a size of about 100 nm with light having a wavelength of 630 nm irradiated from the pinhole 6, the pinhole 6 and the recording film 9 are required.
Should be approximately 34 nm or less.

Since 1 / γ <λ is satisfied in the region of D << λ, the flying height of the slider 1 needs to be smaller than the wavelength of the light incident on the pinhole 6. DVD
In a ROM, using a light spot of about 1 μm,
A recording density of about 3 Gb / in2 is realized. The first
In the example, when the size D of the light spot is 100 nm, the recording density can be 300 Gb / in2.

Thus, when a pinhole is provided in a slider and information is recorded / reproduced using light irradiated from the pinhole, the positioning of the pinhole and the surface of the slider facing the information recording medium is extremely precise. Need to be done. That is, the sum h of the step size of the core 15 with respect to the clad 16 and the flying height of the slider 1 in FIG.
It is necessary to be 33 nm or less.

In the method of the present invention, since the pinhole 6 is provided directly on the surface of the slider 1 facing the information recording medium 2, no positioning problem occurs. Further, as described above, since the pinhole 6 is provided in the recessed portion provided in the core 15, the probability that the pinhole 6 collides with the information recording medium 2 and is broken is extremely small.

FIG. 4 is a perspective view of an information recording / reproducing apparatus to which the optical element according to the present invention is applied. The information recording medium 2 has a disk shape and is rotated by a spindle motor 22 fixed to a base 21. With this rotational movement,
It moves relative to the slider 1. Positioning actuator 2
3 is also fixed to the base 21, and the arm 3 is fixed to the movable part. The positioning actuator 23 rotates around its axis, and moves the slider 1 attached to the tip of the arm 3 in the radial direction of the information recording medium 2.

The structures of the slider 1 and the information recording medium 2 are the same as those of the slider 1 and the information recording medium 2 of FIG.
The interface 24 fixed to the base 21 has a connector 25, and receives power from the cable connected to the connector 25 for driving the apparatus.
The information recording / reproducing command to the device, the input of the information to be recorded, and the output of the information to be reproduced are performed.

When the interface 24 receives a command for recording or reproducing information from outside the apparatus, the interface 24 transmits the command to the system controller 2.
Enter 6 The system controller 26 receiving this command supplies power to the spindle motor 22 to rotate the information recording medium 2.

As described with reference to FIG. 1, the slider 1 moves relative to the information recording medium 2 while maintaining a constant flying height. The system controller 26 further turns on the laser light source 27. The light emitted from the laser light source 27 is incident on the optical fiber 4 which is not clearly shown in FIG. 4, and the information recording medium 2 is irradiated with the light through the pinhole 6.

The system controller 26 turns on the laser light source 27 and receives a signal from the photodetector 14 at the same time. On the information recording medium 2, a row of marks on which information is recorded, which is called a track, is provided concentrically. As will be described later, each track is provided with a mark for identifying the track and a mark for identifying a deviation from the track.

For this reason, the system controller 26
From the signal from the photodetector 14, it is possible to determine on which track the pinhole 6 on the information recording medium 2 is located and how much the pinhole 6 is displaced from the track.

The system controller 26 compares the position at which information specified by an instruction from the outside of the apparatus is to be recorded or reproduced with the actual position of the pinhole 6 obtained from the signal of the photodetector 14. Based on the comparison result, the positioning actuator 23 is driven to position the pinhole 6 on a predetermined track on the information recording medium 2.

After the positioning, if the command from the outside of the apparatus is to reproduce information, the system controller 2
6 causes the laser light source 27 to emit light at a constant intensity. This emission intensity is an intensity that does not destroy information recorded on the recording film 9.

A recording mark is formed on the information recording medium 2 by removing a part of the recording film 9 or changing the direction of magnetization of the recording film 9. The information is reproduced by detecting, with the photodetector 14, the transmitted light amount of the light that has passed through and radiated to the recording film 9.

As described above, the photodetector 14 has the recording film 9
Has a function of detecting information on the polarization direction of the light transmitted through the light. The information detected by the photodetector 14 is subjected to processing such as error correction by the system controller 26 and then output from the interface 24 to the outside of the apparatus.

When the command from the outside of the apparatus is to record information, the system controller 26 modulates the intensity of light emitted from the laser light source 27 in accordance with the information to be recorded, and Modulates the current flowing through
Recording of information is performed by changing the direction of magnetization of the recording film 9. This is a magnetic field modulation method used in a magneto-optical disk device.

Light is emitted from the laser light source 27 through the pinhole 6 to raise the temperature of the recording film 9 at the location where information is to be recorded to a Curie temperature or higher. At the same time, a current is applied to the coil 7 to apply a magnetic field to the portion of the recording film 9 where the temperature has risen. When the laser light source 27 stops emitting light, the temperature of the recording film 9 decreases, and the recording film 9 is magnetized in the direction of the applied magnetic field.

Depending on whether the direction of the applied magnetic field is directed upward or downward in FIG. 1, the magnetization of the portion of the recording film 9 irradiated with light is directed upward or downward. Information is recorded by alternately arranging the upwardly magnetized portion and the downwardly magnetized portion.

FIG. 5 is an enlarged view of the vicinity of the arm 3. FIG. 5 (A) is a plan view of the arm 3, and FIG. 5 (B) is a side view. The portion of the arm 3 described as Ls in FIG. 5 acts as a spring, and follows the surface fluctuation of the rotating information recording medium 2.

The optical fiber 4 is fixed to the arm 3 by fixing jigs 31 and 32. One end of a portion of the optical fiber 4 closer to the slider 1 than the fixing jig 31 is fixed to the slider 1, and the other end is fixed to the fixing jig 31. As shown in FIG.
Is attached before the part written as Ls.

Therefore, when the portion of the optical fiber 4 between the fixing jig 31 and the slider 1 is bent as shown in FIG. Act on the part. Among the reaction forces, the reaction force acting on the slider 1 and the reaction force acting on the fixing jig 31 completely cancel each other according to the law of the action reaction.

Therefore, the reaction force when the optical fiber 4 is bent as shown in FIG. 5 is substantially the same as that which does not act on the portion of the arm 3 where Ls is written. It is not necessary to consider the spring action of No. 3. Since the optical fiber 4 is further fixed to the arm 3 by the fixing jig 32, the rigidity of the portion of the optical fiber 4 between the fixing jigs 31 and 32 affects the spring action of the arm 3.

This effect is caused by increasing the distance Lf between the fixing jigs 31 and 32 in FIG. 5 and fixing the optical fiber 4 even when an ordinary optical fiber having an outer diameter of 125 μm is used as the optical fiber 4. By lowering the rigidity between the jigs 31 and 32, the rigidity can be reduced to a level at which there is no practical problem. Also, reducing the outer diameter of the optical fiber 4 is effective in reducing the rigidity of the optical fiber 4.

However, since light leaks from the core 15 to the clad 16, the thickness of the clad 16 needs to be sufficiently larger than the wavelength of light emitted from the laser light source 27. 10 times the wavelength of the light emitted from the

For example, when the wavelength of light emitted from the laser light source 27 is 630 nm, the thickness of the clad 16 needs to be 6.3 μm or more. Therefore, core 1
The length obtained by adding twice this 6.3 μm to the diameter D of 5,
This is the lower limit of the diameter of the optical fiber 4. Since the lower limit of the diameter D of the core 15 is about 0.6 μm, the lower limit of the diameter of the optical fiber 4 is about 12.9 μm.

From the viewpoint of rigidity, the smaller the diameter of the optical fiber 4 is, the better it is. From the viewpoint of rigidity, an ordinary optical fiber for communication can be used. From these, for example,
When the wavelength of the light emitted from the laser light source 27 is 630 nm, the outer diameter of the optical fiber is 12.4 μm to 12 μm.
What is necessary is that it is between 5 μm.

Although the frictional force between the optical fiber 4 and the arm 3 also affects the spring operation of the arm 3, as shown in FIG. 5, by holding the optical fiber 4 floating from the arm 3, the frictional force is reduced. The effects can be removed.

The arm 3 is attached to the positioning actuator 23. At the base of the arm 3, a laser light source 27 is attached. The laser light source 27
It comprises a semiconductor laser 34 and a fiber holder 33. Light emitted from the semiconductor laser 34 is coupled to the optical fiber 4. The fiber holder 33 holds the optical fiber 4
Is fixed at the position of the active layer of the semiconductor laser 34.

The light radiated from the semiconductor laser 34 enters the optical fiber 4 and the pinhole 6 of the slider 1 is
And is irradiated on the information recording medium 2. The semiconductor laser 34 is fixed so that the polarization direction of the emitted light is up and down in the side view of FIG. Since the optical fiber 4 is simply bent in one direction, the metal film 5
Is P-polarized when it is incident on. Optical fiber 4
, A polarization maintaining fiber may be used.

The semiconductor laser 34 is connected to the system controller 26 and blinks according to a command from the system controller 26. Since the semiconductor laser 34 and the optical fiber holder 33 are actually quite heavy components, as shown in FIG.
In particular, it is desirable to bring it near the rotation axis of the positioning actuator 23.

FIG. 6 is an enlarged view of the surface of the information recording medium 2. In FIG. 6, a white mark is arranged on a dark gray background and a gray crescent mark lighter than the background. A dark gray portion indicates that the recording film 9 is magnetized upward as shown in FIG. 3, a white portion indicates that the recording film 9 has been removed therefrom, and a light gray portion indicates ,
As shown in FIG. 3, this indicates that the portion is magnetized downward.

Since the transmittance is higher in a portion where the recording film 9 is not present than in a portion where the recording film 9 is present, gray and white light and dark are given according to the transmittance. 6, six tracks 41 to 46 are indicated by dotted lines. Originally, the track is circular, but since the track is partially enlarged, it looks like a straight line in FIG.

Each track is provided with a track identification mark 47. This mark is different for each track, and the mark identifies on which track the pinhole 6 is located. Each track has
Further, a wobble mark 48 and a prediction mark 49 are provided.

The pinhole 6 moves relative to the information recording medium 2 from bottom to top in FIG. Foresight mark 49
Indicates that the wobble mark 48 comes after this. Therefore, the prediction mark 49 is the wobble mark 48
It is composed of a pattern that is not used except for the location immediately before.

A wobble mark 48 indicates a track
The mark is composed of two marks shifted left and right, and is a mark for detecting a shift between the pinhole 6 and the track. For example, it is assumed that the pinhole 6 has passed near the track 46 along a solid line 51 near the track 46. The photodetector 14 detects two light pulses by the marks 52 and 53 when the pinhole 6 passes the wobble mark 48 after the light pulse after passing the prediction mark 49.

When the locus of the pinhole 6 is shifted to the left from the track 46 as indicated by a solid line 51, the mark 52
, Passes near the center of the mark, and the mark 53 passes away from the center. For this reason, of the two light pulses, the first pulse is strong, and the second pulse is weak.

The mark portion is a portion where the light transmittance is high. If the trajectory of the pinhole 6 is shifted to the right with respect to the track 46, the first light pulse is weakened, and the subsequent light pulse is weakened. Become stronger. The track of pinhole 6 is track 4
If they were just riding on 6, the intensity of the two light pulses would be equal.

The system controller 26 compares the magnitude of the two light pulses immediately after the light pulse corresponding to the prediction mark 49, and determines to which and how much the trajectory of the pinhole 6 deviates from the track. Can be requested. A signal indicating this deviation is called a track error signal.

In both the recording mark 50 and the identification mark 47 recorded by a command from the outside of the apparatus,
The pinhole 6 can obtain the largest signal (in this case, an optical pulse) when passing just above the track.
In the reproduction of information, in order to reduce errors in the reproduced information, the larger the signal, the more desirable.

For this purpose, the system controller 26
Drives the positioning actuator 23 based on the track error signal, and positions the pinhole 6 just above a predetermined track. In the case of recording information,
In consideration of the case where recorded information is reproduced, recording is performed by positioning on a track.

In FIG. 6, the identification mark 47, the wobble mark 48, and the prediction mark 49 are formed by removing the recording film 9, while the recording mark 40 is formed by the direction of magnetization. The transmittance of the identification mark 47, the wobble mark 48, and the prediction mark 49 increases, and the transmittance of the recording mark 40 does not change. Therefore, it can be determined from the transmitted light amount whether the mark is a mark indicating the position of the pinhole 6 or recorded information.

Also, information can be recorded and reproduced in the same manner even if the recording film 9 is not a magneto-optical film but a phase change film used in a phase change type optical disk device. In this case, the coil 7 becomes unnecessary.

A second example of the embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a diagram showing a side surface and a cross section of the optical element of the present invention. The slider 61 is a side view, and the slider 71 is a cross-sectional view. FIG. 8 shows FIG.
FIG. 9 is a perspective view of the information recording / reproducing apparatus, FIG. 10 is a structural view near the carriage 80, and FIG. 11 is a perspective view of the slider 61.

The slider 61 shown in FIG. 7 moves relative to the information recording medium 2 at a relative speed v. Slider 61
, A fluid force due to the relative motion with the information recording medium 2 is acting. The slider 61 is supported by the arm 3, and at a position where the above-mentioned fluid force and the spring force of the arm 3 are balanced, the slider 61 relatively moves while keeping a constant distance from the information recording medium 2.

The slider 71 moves relative to the information recording medium 2 at a relative speed v. The slider 71 has
Fluid force due to relative movement with the information recording medium 2 acts. The slider 71 is supported by an arm 72. At a position where the above-mentioned fluid force and the spring force of the arm 72 are balanced, the slider 71 is relatively moved while keeping a constant distance from the information recording medium 2.

The slider 61 has an optical waveguide 64 and a semiconductor laser 62. The optical waveguide 64 is attached to a side surface of the slider 61, and one end surface of the optical waveguide 64 appears on a surface of the slider 61 facing the information recording medium 2. A metal film 65 is provided on this end face, and a pinhole 66 is provided in the metal film 65.
Light emitted from the semiconductor laser 62 is coupled to the optical waveguide 64, propagates in the optical waveguide 64, and enters the pinhole 66.

As shown in FIG. 7, the direction in which light propagates from the semiconductor laser 62 to the
The end face of the optical waveguide 64 provided with is inclined. The semiconductor laser 62 is a normal edge emitting semiconductor laser, oscillates in the TE mode, and the electric field vector is
1, that is, in the plane of FIG. 7. Therefore, light emitted from the semiconductor laser 62 and incident on the pinhole 66 is incident on the metal film 65 as P-polarized light.

As in the case of the first example, surface plasmons are excited in the metal film 65. As described later, this surface plasmon is collected in the pinhole 66 and scattered at the edge of the pinhole 66. The light generated by the scattering of the surface plasmon at the edge of the pinhole 66 is transmitted to the information recording medium 2.
Is irradiated.

The size of the pinhole 66 is smaller than the wavelength of the light emitted from the semiconductor laser 62 and is smaller than the wavelength of the light emitted from the semiconductor laser 62 on the information recording medium 2. Can be read. The distance between the pinhole 66 and the information recording medium 2 is the same as in the case of the first example.

The semiconductor laser 62 is die-bonded on the electrode film 75 provided on the side surface of the slider 61. The cable 63 is composed of two conductors insulated from each other, one of which is connected to the electrode film 75 and the other is connected to the upper surface of the semiconductor laser 62. A current for lighting the semiconductor laser 62 is provided by a cable 63. The structure and function of the information recording medium 2 are the same as those in the first example.

After passing through the pinhole 66, the information recording medium 2
Is transmitted through the information recording medium 2 and is incident on the polarizing element 69 provided on the slider 71. Polarizing element 6
Numeral 9 transmits only linearly polarized light components in a specific direction out of the light transmitted through the information recording medium 2. This transmitted light is the light detector 7
0 is detected.

The direction of the linearly polarized light transmitted through the polarizing element 69 is set at a direction inclined by 45 degrees with respect to the polarization direction of the light applied to the information recording medium 2 from the pinhole 66. By doing so, light having a constant intensity is emitted from the semiconductor laser 62 and the intensity of the light detected by the light detection element 70 is observed, whereby information recorded on the information recording medium 2 can be reproduced. .

The slider 71 is provided with a coil 67. When information is recorded on the information recording medium 2, the semiconductor laser 62 is turned on and off in accordance with the information to be recorded, and at the same time, a current is passed through the coil 67. Information is recorded on the information recording medium 2 as in the case of the first example. Transmission of a signal from the light detection element 70 and supply of current to the coil 67 are performed via a cable 68.

FIG. 8 is an enlarged view of the vicinity of the pinhole 66. FIG. 8A is a longitudinal sectional view, and FIG. 8B is a transverse sectional view. The optical waveguide 64 shown in FIG. 7 includes the core 74 and the clad 73 shown in FIG. Regarding the material of the clad 73 and the core 74, any material may be used as long as both materials are transparent to the light emitted from the semiconductor laser 62 and the refractive index of the core 74 is larger than the refractive index of the clad 73. For example, the material of the clad 73 is SiO2, and the material of the core 74 is Si3.
N4.

The normal of the end face of the optical waveguide 64 is
4 is tilted by an angle θ with respect to the direction in which light propagates. A metal film 65 is formed on this end face. The material of the metal film 65 is the same as in the case of the first example. The metal film 65 is provided with a pinhole 66, and this pinhole 66 can be processed using, for example, a focused ion beam.

As described above, the polarization direction of the light propagating in the optical waveguide 64 and entering the end face is, as described above, the direction in which the light propagates in the optical waveguide 64 and the plane in which the normal of the end face of the optical waveguide 64 extends. is there. That is, P-polarized light is applied to the metal film 65. Therefore, when the incident angle θ with respect to the metal film 65 satisfies a certain condition, surface plasmons can be excited at the interface between the metal film 65 and the outer space as in the case of the first example.

The dimensions of the core 74 are such that the film thickness is H and the width is B. As described above, since the end face is inclined by the angle θ, the cross-sectional shape of the core 74 that appears on the end face has a height H and a width B.
/ sinθ. When the optical waveguide 64 is formed by a normal film forming process, the thickness H of the core 74 is 0.1.
And the width B of the core 74 is also 0.1 to several μm.

The magnitude of the angle θ is basically the same as in the first example. However, as described above, when the material of the core 74 is Si 3 N 4 and the material of the clad 73 is SiO 2, the confinement of light by the core 74 is strong, and the refractive index nf of the core 15 in the first example is It is necessary to replace the equivalent refractive index neq for the TE mode.

As for the deviation of the angle θ, the length of the major axis in the first example is represented by D / sin θ, and
The same discussion can be made by replacing the width B / sin θ of the sectional shape of FIG. The excited surface plasmon propagates in a positive direction with respect to the x-axis in FIG. 8, as shown in FIG. The thickness of the metal film 65 is the same as the thickness of the metal film 5 in the first example.

As shown in FIG. 8, the metal film 65 has a parabolic edge in the end face of the optical waveguide 64. This parabola has its x-axis in FIG. 8 as its axis. As described above, the surface plasmon excited at the interface between the metal film 65 and the space propagates in the positive direction of the x-axis. This surface plasmon is incident on the parabolic edge and is reflected at the edge. Due to the nature of the parabola, the reflected surface plasmons are focused on the parabola. A pinhole 66 is provided at the position of this focal point.

To increase the amount of light emitted from the pinhole 66 to the information recording medium 2 as much as possible, the optical waveguide 6
It is necessary to convert the light propagating in 4 into surface plasmons as much as possible and collect them in pinholes 66. Most of the light propagating in the optical waveguide 64 is confined in the core 74, and in order to convert as much light as possible to surface plasmons, the metal film 65 needs to have at least FIG.
It is necessary to cover the end face of the core 74 as shown in FIG.

As shown in FIG. 8, the center of the core 74 is
Let the origin of the coordinates be the shape of the parabola expressed by equation (9). In order for the metal film 65 to cover the end face of the core 74, it is necessary to use Equations 10 and 11.

[0129]

(Equation 9)

[0130]

(Equation 10)

[0131]

[Equation 11]

For example, when the thickness H of the core 74 is 2.8 μm,
When the width B / sin θ of the cross-sectional shape of the core 74 appearing on the end face is 2.2 μm, x0 = 2 μm, 0 <f <0.54.
It may be 4 μm. In this case, the distance L between the intersection of the x-axis and the parabola and the pinhole may be the same as the above-mentioned f.

FIG. 9 shows a configuration of an apparatus in which the second example of the embodiment of the present invention is applied to an information recording / reproducing apparatus. 9A is an external view of the apparatus, and FIG. 9B is a lower view.
Is a view showing a state where the lid 29 is removed. A connector 25 is attached to the base 21. As in the case of the first example, in addition to receiving power supply for driving the present apparatus, a command for recording / reproducing information to the apparatus and an instruction of information to be recorded are provided. Input and output information to be reproduced.

As described above, the distance between the surface of the slider 61 facing the information recording medium 2 and the information recording medium 2 needs to be very small, and dust in the air can be removed between the slider 61 and the information recording medium 2. When it enters, the information recording medium 2 is destroyed, and the recorded information is lost. For this reason, it is necessary to clean the air in the space where the information recording medium 2 and the slider 61 exist by a method such as assembling the apparatus in a clean room. Further, the lid 29 restricts the inflow and outflow of air from the outside.

As in the case of the first example, the information recording medium 2 has a disk shape and is rotated by a spindle motor 22 fixed to a base 21. This rotational movement causes relative movement with the sliders 61 and 71. In FIG.
Although not shown in FIG. 9, the slider 71 is hidden under the shadow of the information recording medium 2, but is located below the information recording medium 2.

The pivot 81 is fixed to the base 21, and the carriage 80 is rotatable around the pivot 81. The arm 3 is provided on the carriage 80.
A slider 61 is attached to the tip of the slider. The structure of the slider 61 is as described above.

As will be described later, in addition to the arm 3 and the slider 61 clearly shown in FIG. 9, the carriage 80 has another set of the arm 3 and the slider 61, and two sets of the arm 72 and the slider 71. Installed. Although a coil 92 described later is further attached to the carriage 80, it is hidden by the magnetic circuit 82 in FIG.

A magnetic field is applied to the coil 92 by the magnetic circuit 82. When a current flows, a moment around the pivot 81 is generated, and the carriage 80 is rotated around the pivot 81. That is, the carriage 80, the pivot 81, the magnetic circuit 82, and the coil 92 constitute what corresponds to the positioning actuator 23 in the first example. The interface 24 and the system controller 26 in the first example are below the base 21 in FIG. 9, and are shaded by the base 21 in FIG.

The semiconductor laser 34 of the first example
However, in the second example, the coil 7 in the first example becomes the semiconductor laser 62 and is attached to the slider 61, and the coil 7 in the first example becomes the coil 67 in the second example and is attached to the slider 71. In the second example, the photodetector 14 in the first example is a photodetector 70 in the second example, and the photodetector 14 is attached to the slider 71. There are certain differences from the information recording / reproducing apparatus in the first example. Other operations are the same as in the first example.

FIG. 10 is an enlarged view of the vicinity of the carriage 80. 10A is a plan view, and FIG. 10B is a side view. Two arms 3 and two arms 72 are attached to the carriage 80. A slider 61 is attached to a tip of each arm 3, and a slider 71 is attached to a tip of an arm 72. The upper pair of sliders 61 and 71 is attached to the upper information recording medium 2 in the side view of FIG.
The recording and reproduction of information is performed with respect to
Reference numeral 71 records and reproduces information on the lower information recording medium 2.

A coil 92 is mounted on the carriage 80. As shown in the plan view of FIG. 10A, the magnetic circuit 82 applies magnetic fields in opposite directions to the upper side and the lower side of the coil 92 in the plan view. Therefore,
When a current flows through the coil 92, a moment acts on the coil 92 to rotate the carriage 80 around the pivot 81.

By this moment, the carriage 80 rotates around the pivot 81, and the two sliders 61 and 2
The sliders 71 move in the radial direction of the information recording medium 2. With this operation, the opening 66 follows a predetermined track.

As described above, by employing a structure in which a plurality of arms are attached to one carriage, a plurality of sliders can be moved simultaneously. The slider 61 and the slider 71 move at the same time, and record and reproduce information. Also,
When the information recording / reproducing apparatus has a structure having two or more information recording media, the information recording capacity per apparatus can be increased.

FIG. 11 is a perspective view of the slider 61. FIG. On the side surface of the slider 61, an optical waveguide 64 composed of a clad 73 and a core 74, and an electrode film 75 are provided. The semiconductor laser 62 is die-bonded to the electrode film 75.

[0145]

According to the present invention, a pinhole having a sufficient transmitted light rate is mounted on a slider, information can be transferred at a high speed, and information can be recorded at a higher density than a conventional optical disk device. A recording / reproducing device can be configured.

[Brief description of the drawings]

FIG. 1 is a sectional view of a slider according to the present invention.

FIG. 2 is an enlarged sectional view near a pinhole in FIG.

FIG. 3 is an enlarged sectional view near a pinhole in FIG. 2;

FIG. 4 is a perspective view of an information recording / reproducing apparatus to which the optical element of the present invention is applied.

FIG. 5 is an enlarged view of the vicinity of an arm according to the present invention.

FIG. 6 is an enlarged view of an information recording medium surface of the information recording / reproducing apparatus.

FIG. 7 is a sectional view and a side view of a slider according to the present invention.

FIG. 8 is an enlarged sectional view near a pinhole in FIG. 7;

FIG. 9 is a perspective view of an information recording / reproducing apparatus to which the optical element of the present invention is applied.

FIG. 10 is an enlarged view of the vicinity of the carriage in FIG.

FIG. 11 is a perspective view of the slider in FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slider 2 Information recording medium 3 Arm 4 Optical fiber 5 Metal film 6 Pinhole 7 Coil 8 Cable 9 Recording film 10 Substrate 11 Lens 12 Wollaston prism 13 Photodiode 14 Photodetector 15 Core 15 16 Cladding 17 Pinhole 6 Edge Reference Signs List 22 spindle motor 23 positioning actuator 24 interface 26 system controller 27 laser light source 34 semiconductor laser 61 slider 62 semiconductor laser 63 cable 64 optical waveguide 65 metal film 66 pinhole 67 coil 68 cable 69 polarizing element 70 photodetector 71 slider 73 clad 74 core

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Atsushi Kikukawa 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama F-term in Hitachi, Ltd. Basic Research Laboratory (Reference) 2H050 AB03Z AC03 AC42 AC87 AC90 5D119 AA11 CA06 EC24 JA36 JA59 JA64 MA06 NA05

Claims (10)

[Claims] 1. An end face formed obliquely to an optical axis of an optical waveguide has a metal film having a pinhole facing an information recording medium, and an angle formed between the end face and the optical axis. Is an angle at which surface plasmons are excited in the metal film. 2. A light source comprising: a light source; an optical waveguide for transmitting light from the light source; and a slider including the optical waveguide and moving relative to the information recording medium, facing the information recording medium. A metal film is formed on an end face of the optical waveguide, and in an optical element in which a pinhole is formed in the metal film, the end face of the optical waveguide on which the metal film having the pinhole is formed passes through the inside of the optical waveguide. An optical element which is inclined at a predetermined angle with respect to the direction of propagating light. 3. The optical element according to claim 2, wherein an angle between a direction of light propagating in the optical waveguide and a normal to an end face on which the metal film is formed is radiated from the light source. An optical element having an angle to excite surface plasmons on the metal film with respect to the emitted light. 4. The optical element according to claim 1, wherein the end face having the metal film has an elliptical shape.
Assuming that the position of the pinhole is on the major axis of the elliptical shape, the angle between the optical axis and the normal to the end face is θ, and the diameter of the core is d, the position of the pinhole is ｛from the edge of the elliptical shape. (Ds
inθ) / 4 °. 5. The optical element according to claim 1, wherein the core of the optical waveguide has a circular cross section perpendicular to an optical axis, and an end face of the core on which the metal film is formed is elliptical. In the case, the pinhole is located on the major axis of the ellipse, and there is a step between the core and the clad at the end face of the optical waveguide, and the position of the pinhole on the major axis of the ellipse is The angle between the optical axis and the normal to the end face is θ,
An optical element characterized in that when the diameter of the core is d, the core is separated from the edge of the ellipse of the core end face by {(d · sin θ) / 4}. 6. The optical element according to claim 1, wherein a metal film on an end face of the optical waveguide is made of an opaque material, and a part of an edge of the metal film has a parabolic shape. An optical element, wherein the pinhole is formed at a focus position of the parabola. 7. An optical element according to claim 1, wherein said optical waveguide is an optical fiber. 8. An optical element according to claim 1, an information recording medium relatively moving with respect to said optical element, and detecting light irradiated on said information recording medium by said optical element. And an optical detector for reading information recorded on the information recording medium. 9. An information recording medium on or from which information can be recorded or reproduced by optical means, an optical element for irradiating a predetermined area of the information recording medium with light, and an optical element for irradiating the information recording medium with the optical element. A light detector that detects transmitted light, reflected light or scattered light of the light, and reads information recorded on the information recording medium, and outputs information read by the light detector to the outside of the device, and An interface for receiving an instruction from the device, a mechanism system for relatively moving the information recording medium and the optical element, and comparing an instruction input from outside the device via the interface with information read by the photodetector. A servo circuit for driving the mechanical system based on the comparison result to position the optical element at a predetermined position on the information recording medium. And the optical element, claim 1
An information recording / reproducing apparatus, which is the optical element according to claim 7. 10. An information recording medium on or from which information can be recorded or reproduced by optical means, an optical element for irradiating a predetermined area of the information recording medium with light, and an optical element for irradiating the information recording medium with the optical element. A light detector that detects transmitted light, reflected light or scattered light of the light, and reads information recorded on the information recording medium, and outputs information read by the light detector to the outside of the device, and An interface for receiving an instruction from the device, a mechanism system for relatively moving the information recording medium and the optical element, and comparing an instruction input from outside the device via the interface with information read by the photodetector. A servo circuit that drives the mechanism based on the comparison result to position the optical element at a predetermined position on the information recording medium. Wherein the optical element is an optical element in which an end face of an optical waveguide or an optical fiber facing the information recording medium is inclined with respect to a direction of light propagating in the optical waveguide or the optical fiber. Information recording and reproducing apparatus.