JP2000329773A - Near field light source and near field optical recorder/ reproducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a near field light of a high output by introducing a light emitted from a laser to a probe of a near field light source for generating a near field light, and forming an at least portion of the probe in a resonator structure. SOLUTION: A glass fiber 1 sharpened at its one side end face has a first dielectric layer 2, a second dielectric layer 3 and an exciting light source 4 for exciting a near field light. A plurality of the layers 2 and 3 are alternately superposed to form a dielectric multilayer film mirror 50. A resonator structure is formed of the mirror 50 and an end face 51 which is not brought into contact with the mirror 50 of the fiber 1. With the above constitution, an incident light 5 incident from the light source 4 to the fiber 1 through the mirror 50 is amplified in the fiber 1 by the structure. A near field light 6 is generated in proportion to an intensity of the amplified light. Accordingly, an optical amplification factor of the structure is improved to improve a generating efficiency of the light 6 to the light 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a near-field light source and a recording / reproducing apparatus using near-field light, and more particularly to a method of generating near-field light of high output by generating near-field light from a probe or a solid-state laser. The present invention relates to a near-field light source and a near-field optical recording / reproducing device.

[0002]

2. Description of the Related Art In the field of optical measurement, particularly in the field of material surface shape measurement, research and development of a high-magnification optical microscope have been advanced, and detailed measurement using near-field light has been performed. In the field of optical information processing, attempts have been made to perform higher-density recording by using near-field light.

[0003] Near-field light is non-propagating light localized near the surface generated when light is incident on a substance. In particular, when the dimension of a substance is smaller than the incident wavelength, the localized volume of the near-field light is equal to the dimension of the substance. And about the same. Therefore, by using the near-field light, it has become possible to measure a minute area smaller than the diffraction limit or to realize an optical device having a size smaller than the diffraction limit. In order to use this near-field light in a local micro-region, it is important to create a small substance called a probe to generate near-field light,
Up to now, with the advance of the micromachining process technology, a probe whose tip diameter is sharpened to about several tens nm has been realized.

In general, there are roughly two types of methods for detecting the generation of near-field light. One is a method A shown in FIG. In FIG. 5A, 27 is a probe having a sharpened tip, 28 is a sample, and 30 is a laser light source for illuminating the sample 28. Reference numeral 35 denotes a laser beam for illuminating the sample 28 from the surface side of the sample 28, and 36 denotes a sample 28.
Shows a laser beam when the sample 28 is illuminated from the back surface side of FIG. By irradiating the laser beam 36 from the back side of the sample 28 by using the mirrors 31 and 33, or by irradiating the laser beam 35 from the front side of the sample 28 by using the mirrors 32 and 34, the vicinity of the surface of the sample 28 is , A near-field light 37 is generated. In this method, the near-field light 37 is converted into scattered light 38 by inserting a minute tip of the probe 27 into the region where the near-field light 37 exists, and the scattered light intensity is detected. In the figure, reference numeral 29 denotes a prism for realizing the irradiation of the laser beam 36 from the back side of the sample 28 and the fixing of the sample 28.

The other is a method B shown in FIG. In FIG. 5B, reference numeral 39 denotes a probe having a sharpened tip, reference numeral 40 denotes a sample, reference numeral 41 denotes a laser light source, reference numeral 42 denotes laser light from the laser light source 41, and reference numeral 43 denotes near-field light.
In this case, the laser light 42 from the laser light source 41 is incident on the probe 39 to generate near-field light 43 near the sharpened tip of the probe 39. Is converted into scattered light 44, and the scattered light intensity is detected.

Hitherto, a high-density optical recording technique utilizing near-field light by using the above-described method A or B has been developed. For example, a probe that is a near-field light source is brought close to minute irregularities formed on the surface of a substance to convert the near-field light into scattered light, and the probe position and the intensity of the detected scattered light are treated as information. There is technology. In such near-field optical recording, from the viewpoint of the structure of the optical device and the scattered light detection system, etc., it is considered that the above method B is effective. As the near-field light source in this method,
Generally, a processed glass fiber is used as a probe. Advances in microfabrication process technology have made it possible to process the glass fiber tip to several tens of nanometers, and recording and reproduction experiments on magnetic recording materials and phase-change recording materials have been carried out, achieving a minimum recording dimension of 60 to 80 nm in diameter. Was. These are 100-170 Gbit / inc
corresponds to the recording density of h ^2.

On the other hand, in reproduction using near-field light, the generation efficiency of near-field light with respect to incident light (= near-field light intensity / incident light intensity) is about 1 × 10 ⁻⁵ due to limitations due to the probe shape.
To 10 ^-3 , which causes a problem that the data transmission time is delayed. It is important to increase the near-field light power in order to increase the data transmission time. Therefore, when using a conventional probe, it is necessary to increase the power of the incident light. As another method for increasing the data transmission speed, a method using a plurality of probes has been proposed, but there is a problem that a scattered light detection system becomes complicated. In order to realize high-density optical recording, the data transmission speed at the time of data reproduction is important. As means for increasing the transmission speed, parallel reading using a probe array in which probes are two-dimensionally arranged has been proposed. Further, the near-field light power generated with respect to the incident light power to the probe, that is, the near-field light generation efficiency of the probe is greatly related to the transmission speed during reproduction, and the higher the near-field light generation efficiency, the higher the transmission speed. be able to. Until now, the glass fiber was sharpened by chemical etching and placed on a probe formed by depositing a metal film.
A data transmission rate of 0 ^-5 to 1 × 10 ^-3 has been realized, and a data transmission speed of about 50 Mbit / s has been achieved at an incident light power of 1 mW.

[0008]

However, in the conventional near-field light source, the near-field light generation efficiency of the probe is low, and the intensity of the incident light must be increased in order to obtain high-power near-field light. was there. As a result, a high-power laser is required for the incident light source, so that the manufacturing cost of the near-field light generating device is increased and the power consumption is increased.

[0009]

In order to solve the above-mentioned problems, the present invention comprises a laser light source and a probe, which emits light emitted from a laser to the probe and generates near-field light from the probe. A near-field light source characterized in that at least a part of the probe forms a resonator structure.

A probe, a solid-state laser, and a solid-state laser excitation light source are provided. The solid-state laser is fixed to the tip of the probe, and pump light from the solid-state laser excitation light source is incident from the probe to irradiate the solid-state laser. This is a near-field light source that excites laser light and simultaneously generates near-field light, so that a pump light incident portion and a near-field light emitting portion of a solid-state laser are different.

A laser excitation light source and a self-doubling crystal are provided, and a pump light from the laser excitation light source is irradiated on the self-doubling crystal to excite the harmonic laser light and at the same time, a near-field by the harmonic laser light. This is a near-field light source that generates light.

Further, there is provided a near-field optical recording / reproducing apparatus for recording / reproducing data using any of the above-mentioned near-field light sources.

[0013]

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

(Embodiment 1) Here, a point that high near-field light generation efficiency is obtained by forming a part of a probe in a near-field light source into a resonator structure will be described. As an example, a case where a resonator structure including a dielectric multilayer mirror is formed as the resonator structure will be described.

Conventionally, when pump light for exciting near-field light is incident on a probe to generate near-field light at the tip of the probe, there has been a problem that the efficiency of generating near-field light with respect to the incident light is extremely low. In this case, since the near-field light intensity proportional to the light intensity existing inside the probe can be obtained, the near-field light output can be increased by increasing the light intensity inside the probe. Conventionally, this was achieved by increasing the intensity of light incident on the probe.However, since the near-field light generation efficiency of the probe does not change, a high-output incident light source is required, which requires a large-scale device and consumes less power. There was a problem that electric power became large. Therefore, in the present invention, it has been realized that by adding a special structure to a probe that generates near-field light, the near-field light generation efficiency can be greatly improved. In the present invention, by making a part of the probe a resonator structure, low-power incident light can be amplified in the probe, and the light intensity inside the probe can be increased. The generation efficiency could be improved. FIG. 1 shows a configuration diagram of a near-field light source according to the first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a glass fiber having one end face sharpened, 2 denotes a first dielectric layer, 3 denotes a second dielectric layer, and 4 denotes an excitation light source for exciting near-field light. The dielectric multilayer mirror 50 is formed by alternately stacking a plurality of dielectric layers 2 and dielectric layers 3. A resonator structure is formed by the dielectric multilayer mirror 50 and the end face 51 of the glass fiber 1 not in contact with the dielectric multilayer mirror 50. The above configuration excluding the excitation light source 4 is referred to as a probe in the near-field light source of the present invention. In the present embodiment, since the probe has a resonator structure in particular, it is hereinafter referred to as a resonator structure probe. Reference numeral 5 denotes incident light from the excitation light source 4, and reference numeral 6 denotes near-field light generated near the sharpened tip of the glass fiber 1. In the above configuration, the incident light 5 entering the glass fiber 1 from the excitation light source 4 through the dielectric multilayer mirror 50 is amplified in the glass fiber 1 by the above-described resonator structure. Near-field light 6 is generated in proportion to the light intensity of the amplified light. Therefore, the generation efficiency of the near-field light 6 with respect to the incident light 5 can be improved by improving the optical amplification factor of the resonator structure. In this embodiment, an example in which an SiO ₂ layer is used as the first dielectric layer 2, a TiO ₂ layer is used as the second dielectric layer 3, and a semiconductor laser is used as the excitation light source 4 will be described in further detail.

First, polished glass fiber 1
A dielectric multilayer mirror 50 was formed by alternately depositing SiO ₂ as a low-refractive-index material and TiO _{2 as a} high-refractive-index material on one of the end faces. The dielectric multilayer mirror 50 made of these dielectric materials has the advantage of having a high laser damage threshold, and the film can be easily formed by sputtering. At this time, when the thickness of each layer was set to λ / 4, where λ is the wavelength of the incident light, a dielectric multilayer mirror having high reflectance was obtained, and a highly efficient resonator structure could be formed. In the present embodiment, an infrared laser beam having a wavelength λ = 850 nm was used as the incident light 5, so that the SiO ₂ layer (A layer) and the TiO ₂ layer (B
The thickness of each layer was about 2100 °. Further, as the dielectric multilayer mirror 50, each of the A layer and the B layer has 10 layers, and 20 layers.
Layers and 50 layers were prepared. Thereafter, the end face of the glass fiber 1 on the side opposite to the film formation side was subjected to chemical etching and sharpened to form a resonator structure including the dielectric multilayer mirror 50 and the end face 51 of the glass fiber. At this time, the diameter of the tip of the sharpened glass fiber 1 was about 80 nm. Further, aluminum was deposited by vapor deposition on a portion of the tip of the sharpened glass fiber 1 excluding the near-field light emission opening. This can reduce light leakage at the sharpened portion,
The reflectivity of the glass fiber end face 51 acting as a reflection mirror could be increased. In this embodiment, the end face 51 of the glass fiber 1 and the dielectric multilayer mirror 5
The distance to 0 was about 200 μm.

The dielectric multilayer mirror having the above structure
Near-field light source having a cavity structure probe including
Next, its characteristics will be described. First, having a resonator structure
Glass fiber sharpened by chemical etching
And use a probe with just deposited aluminum
When the in-field light generation efficiency was measured, it was about 1 × 10^-6Is the value of
Obtained. On the other hand, a resonator including the dielectric multilayer mirror 50
In the structure probe, the dielectric multilayer mirror 50 is configured.
As the number of dielectric films to be formed increases,
Since the reflectivity of the film mirror 50 increases, the power in the resonator
Density increases, resulting in cavity structure probe tips
The intensity of the near-field light 6 generated from the laser beam also increased. That is,
The generation efficiency of the near-field light 6 with respect to the intensity of the incident light 5 is improved.
In the case where each of the above-mentioned A layer and B layer is 50 layers,
1 × 10^-FourGeneration efficiency was realized. This makes the working length
Resonator structure including 200 μm dielectric multilayer mirror 50
Probe having no resonator structure
Approximately 100 times the near-field light generation efficiency was obtained.
It reproduces data on a recording medium using near-field light.
About 100 times improvement in data transmission speed when compared
It was an expected value. Also, the dielectric multilayer mirror 50
Is made of ZrO as a material having a high refractive index. _Two, Ta_Two
O_Five, Al_TwoO_ThreeAnd use Mg as the low refractive index material
F_TwoThe same dielectric multilayer mirror can be used when using
50 can be formed, and this dielectric multilayer mirror 50 and
Resonator structure probe with glass fiber end face 51
Fabrication has the effect of improving near-field light generation efficiency.
Obtained.

In this embodiment, the dielectric multilayer mirror 50 is formed of two kinds of dielectric materials. However, the dielectric multilayer mirror 50 can be manufactured even when two or more kinds of dielectric materials are used. By forming a similar resonator structure, the near-field generation efficiency could be improved.

Further, a probe having a resonator structure was manufactured by forming a periodic refractive index distribution structure having a period Λ = 2π / β, where β is a propagation constant of the light 5 incident on the probe. Also in this case, it was possible to improve the near-field light generation efficiency. Such a periodic structure is
Distributed Bragg reflection type (Distributed Bra)
gg reflector (DBR) mirror structure (hereinafter abbreviated as DBR mirror structure), which has a periodic refractive index distribution that satisfies the Bragg reflection condition in the light propagation direction, and the propagating light is reflected in the direction opposite to the incident direction. You. The reflectivity at this time depends on the length (action length) of the DBR mirror structure and the cross-sectional area of the periodic structure with respect to the cross-sectional area of the waveguide. Since such a periodic refractive index distribution can be easily manufactured by using a fiber grating manufacturing technique, there is an advantage that a resonator structure probe can be easily manufactured. The fiber grating technology is a technology that changes the refractive index of an exposed portion by exposing an optical fiber to an interference fringe pattern of ultraviolet light. Therefore,
By using an arbitrary mask, it was possible to form the above DBR mirror structure on a part of an optical fiber used as a probe. In addition, DBR
It is possible to arbitrarily form the length of the mirror structure,
There is also an advantage that the reflectance in the DBR mirror structure can be easily selected.

Further, a near-field optical recording / reproducing apparatus using a near-field light source including a resonator structure obtained as described above is manufactured, and a Pt / Co multilayer film as one of magneto-optical recording media is manufactured. A recording and reproduction experiment was performed. At this time, recording was possible at an incident light power of 1 mW. The recording spot size was a very small area of about 80 nm. This corresponds to a recording density of 100 Gbit / inch ² . In addition, a reproduction experiment was performed with this device, and a value about 100 times higher than that of the conventional device was obtained as the transmission speed.

A photonic crystal is used in place of the glass fiber 1, and a photonic crystal structure is manufactured so that light can be confined in the photonic crystal in a direction orthogonal to the dielectric multilayer mirror 50. Even when a resonator structure probe including the dielectric multilayer mirror 50 was formed, light confinement similar to that of the glass fiber 1 was possible, and it could be used as a near-field light source. The end face of the photonic crystal could be easily sharpened by chemical etching, and a sharpened probe tip almost similar to the case where the glass fiber 1 was used could be formed. Even with the near-field light source using this photonic crystal, a near-field light generation efficiency of about 1 × 10 ⁻⁴ was obtained.

(Embodiment 2) In this embodiment, the point that high-power near-field light can be generated by using a solid-state laser at the tip of a probe will be described. As an example, a case where Er: fiber laser and Nd: glass laser are used as the solid state laser will be described.

As described above, when the laser light 42 for exciting near-field light is incident on the probe 39 as shown in FIG. 5B, the efficiency of generating the near-field light 43 by the conventional probe 39 is very high. It is low, and its size is about 1 × 10 ⁻⁵ to 10 ^{−3 with} respect to the intensity of the incident laser beam 42.
It was about. This is largely due to the shape of the probe 39, and it has been difficult to improve the near-field light generation efficiency while maintaining the area of the near-field light generation region by improving the probe shape. In addition, the probe 39
Also, depending on the material constituting the above, the loss of waveguide of the laser light 42 in the probe 39 also causes the decrease in the near-field light generation efficiency. We note that near-field light is also generated on the surface of the solid-state laser, and in this case, consider that it is possible to increase the near-field light generation efficiency with respect to the intensity of the pump light incident on the solid-state laser. In the present invention, an attempt was made to produce a near-field light source using near-field light generated on the surface of a solid-state laser. First, we tried to improve near-field light generation efficiency using a fiber laser.
FIG. 2 shows an example in which an end face of an Er-doped glass fiber according to the second embodiment of the present invention is processed to produce a probe. Reference numeral 7 denotes an Er-doped glass fiber having one end face sharpened, 8 denotes a light source for exciting a solid laser for generating pump light, 9 denotes a light source for signal, 10 denotes a coupling mirror, and 11 denotes a coupling mirror.
Pump light from the solid-state laser excitation light source 8;
Is a signal light from the signal light source 9, and 13 is a generated near-field light. With the pump light 9 from the solid-state laser excitation light source 8 always entering the Er-doped glass fiber 7 through the coupling mirror 10, the signal light 12 from the signal light source 9 is passed through the coupling mirror 10 to Er.
When the light enters the doped glass fiber 7, the light intensity of the signal light 12 is amplified in the Er-doped glass fiber 7,
The near-field light 13 excited by the amplified light is Er
It is generated from the sharpened tip portion of the doped glass fiber 7. In this example, the Er-doped glass fiber 7 was sharpened by chemical etching. At this time, the tip diameter of the sharpened Er-doped glass fiber 7 was about 80 nm. Thereafter, the end face of the Er-doped glass fiber 7 on the opposite side is polished, and the coupling mirror 1 is polished.
A probe was constructed by arranging and adhering 0s.

The characteristics of the above configuration will be described. The Er-doped glass fiber 7 is known as a fiber laser. For example, when a laser having a wavelength of 950 nm is used as the pump light 11 and a laser light having a wavelength of 1550 nm is incident as the signal light 12, the signal light 12 is emitted.
Can be amplified. Also in this embodiment, the generation efficiency of the near-field light 13 with respect to the intensity of the incident signal light 12 is improved by using the laser light of these wavelengths and using the amplified signal light 12 as a light source of the near-field light 13. The near-field generation efficiency has improved several to several tens of times compared to the conventional glass fiber probe. However, since the amplification of the signal light 12 depends on the intensity of the pump light 11, there is a problem that it is necessary to increase the intensity of the pump light 11 in order to obtain high near-field generation efficiency. Therefore,
As another method for improving the near-field generation efficiency, an attempt was made to fabricate a near-field light generation light source as shown in FIG.

FIG. 3 shows an example in which a solid-state laser processed into a sphere is disposed at the tip of the probe as a near-field light generating light source. Reference numeral 14 denotes a solid-state laser processed into a sphere, 15 denotes a light source for exciting the solid-state laser, 16 denotes a lens, and 17 denotes an optical material used for fixing the solid-state laser 14 and the lens 16. Reference numeral 18 denotes pump light from the solid-state laser excitation light source 15, and reference numeral 19 denotes laser light that has multiple reflections in the solid-state laser 14. Reference numeral 20 denotes near-field light generated on the surface of the solid-state laser 14. The pump light 18 from the solid-state laser excitation light source 15 is condensed by the lens 16 and irradiated on the solid-state laser 14 to excite the laser light 19. At this time, by processing the solid-state laser 14 into a spherical shape, the laser light 19 excited in the solid-state laser 14 is multiple-reflected inside the solid-state laser 14, and the laser light intensity in the solid-state laser 14 increases. The near-field light 20 is generated on the surface of the solid-state laser 14 by the increased laser light 19. At this time, by providing a part of the optical material 17 as an opening as shown in FIG. 3, a near-field light emitting portion can be obtained. Further, it is desirable that the optical material 17 is a material having a refractive index close to 1 and transparent to the incident pump light 18. In this embodiment, silicate glass (SiO 2: refractive index 1.55) is used as the solid-state laser 14.
Optical material 1 using Nd: glass laser whose base material is
7 is an example using MgF ₂ (refractive index 1.2).

First, N processed into a spherical shape having a diameter of about 2 μm
d: The glass laser 14 was covered with MgF ₂ 17. At this time, an emission aperture of the near-field light 20 was formed by masking a part of the Nd: glass laser 14. The diameter of this opening was about 80 nm. Further lens 16
Was placed on the upper side of MgF ₂ 17 whose end face was polished to form a near-field light generating probe. As the lens 16, a microlens manufactured by a photolithography process was used. In addition, a high-output semiconductor laser having a wavelength of 808 nm was used as the solid-state laser excitation light source 15.

The characteristics of a near-field light source including a probe having a spherical solid-state laser configured as described above will be described. First, in the present invention, the Nd: glass laser 14 was processed into a spherical shape. Thereby, the incident pump light 1
8 is Nd: a laser beam 19 is excited in the glass laser 14. Since the laser light 19 is multiple-reflected inside the Nd: glass laser 14, it is possible to amplify the laser light contributing to the generation of the near-field light 20 with high efficiency. Further, since the excited / amplified laser light generates the near-field light 20 near the surface of the Nd: glass laser 14, the effect that the near-field light generation efficiency can be greatly increased is obtained. Since Nd: glass has a wide spectrum width, large energy can be stored in the laser medium as population inversion without causing parasitic oscillation. Therefore, the Nd: glass laser 14 has an advantage that it is suitable for a high-power and high-energy laser system. Nd: glass has the advantages of high workability and easy spherical shape, and has the advantage that the laser medium can be made with high optical homogeneity and relatively inexpensively. Further, by arranging the solid-state laser at the tip of the probe, the effect that the waveguide loss of the laser light by the probe, which has conventionally been a problem, can be removed.

The near-field generation efficiency of about 1 × 10 ⁻³ was realized in the probe having the solid-state laser manufactured as described above. This is the near-field light generation efficiency (about 1 × 1) of the conventional sharpened fiber probe (described in Example 1).
It was about 1000 times the values for 0 ^-6). This was a value expected to improve the data transmission speed by about 1000 times.

Further, by adopting the configuration of the near-field light source including the probe having the solid-state laser as in the present embodiment, another effect that the probe can be downsized was obtained.

Further, a near-field optical recording / reproducing apparatus using the near-field light source obtained as described above is manufactured, and a recording / reproducing experiment is performed on a Pt / Co multilayer film as one of the magneto-optical recording media. Was. At this time, recording was possible at an incident light power of 1 mW. The recording spot size is about 80 nm
And a very small area. This is 100Gbit /
Inch ² corresponds to the recording density. In addition, a reproduction experiment was performed with this device, and a value about 100 times higher than that of the conventional device was obtained as the transmission speed.

The solid-state laser 14 is Nd: Y
A similar near-field light generating light source was obtained when an AG laser or a ruby laser was used. The Nd: YAG laser has a feature that the excitation energy is smaller than that of the Nd: glass laser, and has an advantage that the repetition operation is easy. Also, the ruby laser has a high laser oscillation threshold, but has a characteristic that a high output laser beam can be obtained. Further, the oscillation wavelength of the ruby laser is about 0.69 μm, which has an advantage that near-field light can be generated by visible light.

(Embodiment 3) In this embodiment, a self-doubling crystal is used as a part of a probe in a near-field light source to excite a harmonic with respect to incident light, and at the same time, a near-field light corresponding to the harmonic. A description will now be given of the point at which it is possible to generate the error. As an example, a case where an Nd: LiNbO ₃ crystal is used as a self-doubling crystal will be described.

When performing recording using near-field light, thermal mode recording using energy of the near-field light as heat,
Photon mode recording using a photochromic material or the like can be considered, but in the case of photon mode recording, there arises a problem of the wavelength sensitivity characteristics of the recording medium. Near-field light is localized non-propagating light generated on the surface of a substance when the substance is irradiated with laser light. Therefore, it contains a component that depends on the wavelength of the incident light, and the wavelength of the scattered light that is scattered and detected by the interaction between the substance and the probe also depends on the wavelength of the incident light. Therefore, in photon mode recording, the wavelength of incident light for exciting near-field light is important. The absorption wavelength of currently used photochromics has many wavelength bands from ultraviolet to blue, but the wavelength of the near-field light pump light source conventionally used is in the red to infrared wavelength band, so there is a problem that it cannot cope. Was. This is because it is difficult to generate near-field light with high efficiency because the optical fiber used as a probe has absorption in a short wavelength region. Therefore, in the present invention, an attempt was made to generate near-field light in a short wavelength range.

FIG. 4 is a view showing a third embodiment of the present invention. In the near-field light generating probe, a self-doubling crystal is arranged at a portion near the tip of the probe to generate a near-field light having a short wavelength. It is an example of a field light source. 21 is a self-doubling crystal, 22 is a light source for exciting a solid laser, and 23 is a probe made by sharpening a sharpened glass fiber. Reference numeral 24 denotes pump light from the solid-state laser excitation light source 22, reference numeral 25 denotes a harmonic converted by the self-doubling crystal 21, and reference numeral 26 denotes near-field light generated at the sharpened tip of the probe 23. Pump light 24 incident on the probe 23 from the solid-state laser excitation light source 22
The laser light is excited in the self-doubling crystal 21 arranged in the probe 23 by the light, and the harmonics 25 of the excited laser light 25
Occurs. Due to this harmonic 25, near-field light 26 is generated at the tip of the sharpened probe 23. In this embodiment, the solid-state laser excitation light source 22 has a wavelength of 805 nm.
And a Nd: LiNbO ₃ crystal was used as the self-doubling crystal 21. In this embodiment, the self-doubling crystal 21 is arranged in a part of the probe 23. However, even when the Nd: LiNbO ₃ crystal is processed and sharpened, similar near-field light can be generated by the same harmonic. Thus, near-field light generated with high efficiency could be obtained.

The characteristics of the near-field light source configured as described above will be described. First, self-doubling crystal 2
1 will be described. The self-doubling crystal 21 is a crystal having a laser oscillation function and a wavelength conversion function,
By irradiating the self-doubling crystal 21 with the pump light 24, a laser beam (fundamental wave) is excited, and a harmonic 25 corresponding to the fundamental wave is oscillated by a nonlinear optical effect. The self-doubling crystal 21 used in this embodiment is an Nd: LiNbO ₃ crystal,
A fundamental wave (wavelength 94) excited by irradiation with the pump light 24
6 nm) and a second harmonic (wavelength 473 nm) whose wavelength has been converted by the second-order nonlinear optical effect. By using the second harmonic as excitation light for generating near-field light, it has become possible to obtain near-field light having a corresponding wavelength. In the present embodiment, the fundamental wave having a wavelength of 946 nm is excited and oscillated by inputting the pump light 24, and the harmonic 25 having the wavelength of 473 nm and the near-field light 26 generated by the harmonic 25 are obtained by the self-doubling effect. Was completed. In addition, a sharpened optical fiber that had been chemically etched in advance was bonded to the Nd: LiNbO ₃ crystal.
At this time, by setting the length of the optical fiber to about 100 μm, the waveguide loss due to the optical fiber could be reduced.

Further, a resonator structure is formed by the dielectric multilayer mirror 50 or the DBR mirror structure described in the first embodiment and the end face 51 of the glass fiber probe 1, and the above-described self-doubling crystal is formed in the resonator. 2
When No. 1 was arranged, the fundamental wave could be excited using the pump light amplified by the resonator structure, and the harmonics 25 could be generated with high efficiency. High-power near-field light 26 was able to be generated from the tip of the probe using the harmonics 25 thus obtained.

In this embodiment, self-dublin
Er: LiNbO as the crystal 21 _ThreeI used crystals,
When a solid-state laser and a wavelength conversion element are combined
Can generate a harmonic 25,
Excites solid-state laser and converts laser light to wavelength conversion element
To generate a harmonic 25,
5, the near-field light 26 was generated. In this embodiment
In this case, as a wavelength conversion element,
O: LiNbO_ThreePeriodic polarization reversal and optical waveguide in crystal
The formed optical waveguide type SHG element was used. Optical waveguide type S
Conversion from fundamental wave to harmonic by using HG element
It was possible to increase the efficiency. In this case,
The output wavelength is 106 as a solid-state laser that generates a fundamental wave.
An optical waveguide type using a Nd: YAG laser of 0 nm
By combining with SHG element, high wavelength of 530nm
Succeeded in obtaining a harmonic, and using this harmonic,
Light 26 could be generated. SHG is the second
Harmonic generation (secondharmonic gene)
which is incident by wavelength conversion
The element for generating the second harmonic with respect to the fundamental wave is particularly SHG
It is called an element.

[0039]

As described above, in the present invention, as a near-field light source, a part of the near-field light generating probe has a resonator structure to improve the near-field generation efficiency, and to provide a high-power near-field light source. Light generation is now possible. By using this near-field light source, it was possible to improve the data transmission speed during near-field optical recording and reproduction.

Further, with this near-field light source, recording and reproduction can be performed on a magneto-optical recording material and a phase-change recording material using high-power near-field light, and high-density recording and reproduction can be performed.

Further, an inexpensive low-power laser can be used as the incident light source, and the cost of the near-field generating light source can be greatly reduced. Further, there is an effect that power consumption can be reduced.

Further, it is possible to use a solid-state laser medium as a near-field light generating probe and to excite the laser light with pump light and simultaneously generate near-field light on the surface of the solid-state laser, thereby improving near-field light generation efficiency. A near-field light source was realized.

Further, a solid laser medium processed into a spherical shape is arranged at the tip of the probe, and pump light is incident on the solid laser medium to cause multiple reflections of the excited laser light in the solid laser medium, thereby contributing to generation of near-field light. It became possible to amplify laser light. Thereby, the effect of further improving the near-field light generation efficiency was obtained. Further, there is an effect that the near-field light generating probe can be miniaturized.

Further, by arranging a self-doubling crystal at a part of the near-field light generating probe, it was possible to realize near-field light generation by harmonics. This allows
For example, for an optical recording material or the like having sensitivity to a short wavelength, an effect that a near-field optical recording in a photon mode using near-field light of a short wavelength becomes possible is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a configuration of a near-field light source including a near-field light generating probe having a multilayer resonator structure according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a configuration of a near-field light source including a near-field light generating probe including a fiber laser according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a configuration of a near-field light source including a near-field light generating probe having a spherical solid-state laser at a probe tip according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of a configuration of a near-field light source including a near-field light generating probe including a self-doubling crystal according to a third embodiment of the present invention.

FIG. 5 (a) shows an example of an optical system for generating and detecting near-field light by irradiating a sample with laser light. FIG. 5 (b) shows generation and detection of near-field light by entering laser light into a probe. Showing an example of an optical system

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Glass fiber 2 First dielectric layer 3 Second dielectric layer 4 Excitation light source 5 Incident light 6,13,20,26,37,43 Near-field light 7Er-doped glass fiber 8,15,22 Solid state laser excitation Light source 9 Signal light source 10 Coupling mirror 11, 18, 24 Pump light 12 Signal light 14 Solid-state laser 16 Lens 17 Optical material 19, 42 Laser light 21 Self-doubling crystal 23, 27, 39 Probe 25 Harmonic 28, 40 Sample 29 Prism 30, 41 Laser light source 31, 32, 33, 34 Mirror 35 Incident laser light when illuminating the sample from the sample front side 36 Incident laser light when illuminating the sample from the sample back side 38, 44 Scattered light 50 Dielectric Body multilayer mirror 51 end face

Continued on the front page (72) Inventor Kazuhisa Yamamoto 1006 Kazuma Kadoma, Kazuma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F term (reference) 5D119 AA11 AA22 AA43 FA04 FA18 JA28 JA36 JA40 JA44 JA57 5F072 AB01 AB04 AB08 AB09 AK06 AK10 JJ08 KK06 KK12 QQ02 RR03 YY16

Claims (15)

[Claims] 1. A near-field light source comprising: a laser light source; and a probe, wherein light emitted from the laser light source is incident on the probe and generates near-field light from the probe. Has a resonator structure. 2. The near-field light source according to claim 1, wherein the resonator structure includes a DBR mirror structure. 3. The near-field light source according to claim 1, wherein the resonator structure includes a dielectric multilayer mirror. 4. The near-field light source according to claim 3, wherein said dielectric multilayer mirror is made of at least two kinds of materials having different refractive indexes. 5. The near-field light source according to claim 1, wherein the resonator structure includes one of a laser medium, a self-doubling crystal, and a wavelength conversion element. 6. A probe, a solid-state laser, and a solid-state laser excitation light source, wherein the solid-state laser is fixed to a tip portion of the probe, and pump light from the solid-state laser excitation light source is incident from the probe. Irradiating the solid-state laser to excite the laser light and simultaneously generate near-field light, and wherein the pump light incident portion and the near-field light emitting portion of the solid-state laser are different. light source. 7. The near-field light emitting section of the solid-state laser, wherein the near-field light emitting section is sharpened, or a sharpened dielectric is bonded to the solid-state laser to form the near-field light emitting section. The near-field light source according to claim 6. 8. The near-field light source according to claim 6, wherein said solid-state laser is spherical. 9. The near-field light source according to claim 6, wherein said solid-state laser is a fiber laser. 10. The near-field light source according to claim 6, wherein the solid-state laser is one of a Nd: glass laser, a ruby laser, and a YAG laser. 11. A self-doubling crystal, comprising: a laser excitation light source; and a self-doubling crystal arranged at least in a part of a probe, wherein a pump light from the laser excitation light source is applied to the self-doubling crystal to generate a laser beam. ,
A near-field light source that excites a harmonic corresponding to the laser light and simultaneously generates near-field light based on the harmonic. 12. The near-field light source according to claim 11, wherein said self-doubling crystal is a crystal comprising a solid-state laser and a wavelength conversion element. 13. The near-field light source according to claim 12, wherein the wavelength conversion element is an optical waveguide type wavelength conversion element. 14. The near-field light source according to claim 13, wherein the material constituting said optical waveguide type wavelength conversion element is an MgO: LiNbO ₃ crystal. 15. A near-field light source according to any one of claims 1 to 14 and a recording medium, and information is stored in said recording medium by bringing said near-field light source close to said recording medium. A near-field optical recording / reproducing apparatus for recording or reading information recorded on the recording medium.