JP3895076B2 - Optical device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical apparatus that detects the state of optical information of a recording medium or a sample and records or reproduces optical information with a resolution higher than the diffraction limit of light.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, research on increasing the sensitivity of recording media has been actively conducted with the improvement of the recording speed of optical disks. For example, Japanese Patent Laid-Open No. 4-62090 discloses a method for increasing the sensitivity of a recording layer using so-called plasmons.
[0003]
A plasmon is a vibrational quantum of free electrons in a metal or semiconductor. For example, plasmon can be excited by light irradiation. Since this plasmon generates a strong electromagnetic field around it when excited, various applications using this energy are expected.
[0004]
In the above conventional example, microspheres made of a recording material and metal to be modified or melted are dispersed in a recording layer, plasmons are excited on the metal portions of the microspheres by irradiation with laser light, and heat is generated by the generated strong electromagnetic field. The recording sensitivity, that is, the recording efficiency has been improved by generating and recording on the recording material.
[0005]
[Problems to be solved by the invention]
However, in the above conventional example, although the efficiency was improved by using plasmons at the time of recording, there is no disclosure or suggestion of a method of using plasmons at the time of reading. There has been no disclosure or suggestion of a method for recording and reproducing at a high density by reducing the size of the mark.
[0006]
Therefore, in the above conventional example, as the recording density increases, the recording area becomes smaller, so that there is a problem that the output of the read signal from the recording area is reduced by irradiating the recording area with laser light. .
[0007]
[Means for Solving the Problems]
An object of the present invention is to stably perform high-sensitivity optical reproduction using plasmons.
[0008]
In order to solve the above-described problems, an optical apparatus according to the present invention includes an irradiating unit that focuses a light beam on a sample on which information to be optically recorded is recorded by a condensing lens, and enters the light beam. An electromagnetic field is generated by irradiating a light beam on the optical path to the sample, and information is generated from the plasmon part arranged close to the sample and light from the sample irradiated with the light beam. And a hemisphere for making the light beam from the condenser lens smaller than that when propagating through the air and making it incident on the plasmon part and the sample due to the near-field effect. It is characterized by having a lens.
[0009]
According to the above configuration, the sample is optically recorded on the sample from the reflected or transmitted light from the sample based on the light beam by irradiating the sample with the light beam from the irradiating means by condensing the sample with the condenser lens. The recorded information, for example, the image of the sample and the recorded information recorded on the sample can be reproduced by the reproducing means.
[0010]
At this time, in the above configuration, the hemispherical lens is provided on the optical path from the condenser lens to the sample, so that the hemispherical lens has a smaller beam spot diameter than the beam spot diameter collected on the sample by the condenser lens. Therefore, information on a recording area that is a smaller area in the sample can be reproduced more reliably, and it is possible to cope with improvement in image resolution and recording density in the sample.
[0011]
In addition, in the above configuration, the beam spot of the light beam is irradiated and the beam spot is also irradiated to the plasmon portion corresponding to the sample portion to be reproduced, so that the plasmon portion of the irradiated portion is irradiated with the light beam. It becomes possible to perform plasmon excitation, and a strong electromagnetic field by the plasmon excitation can be generated in the plasmon part, and for example, near-field light or heat by the electromagnetic field can be applied to a corresponding region of the sample.
[0012]
Therefore, in the above configuration, for example, when a recording magneto-optical recording medium that records information according to each direction of perpendicular magnetization of each recording region in the sample and reproduces the information by changing the Kerr rotation angle, Even if the Curie temperature of the readout layer in the magneto-optical recording medium is set high in order to set the change in the Kerr rotation angle to a large value, the strong electromagnetic field from the plasmon part, for example, heat generation due to the generation of current due to the strong electromagnetic field from the inside It is possible to quickly generate heat, and not only the heat generated by light beam irradiation but also the heat generated from the plasmon part, the readout layer can be efficiently and quickly heated, and information from the sample is transferred to the plasmon part. By using the generated electromagnetic field, it can be amplified and reproduced.
[0013]
Furthermore, the optical device may include first detection means for detecting a light component contributing to plasmon excitation in the light from the sample.
[0014]
According to the above configuration, since the first detection unit that detects the light component at the angle that contributed to plasmon excitation out of the light from the sample is provided, the light component of the first detection unit, for example, the amount of light is reduced. By detecting the amount, the state of plasmon excitation in the plasmon part can be easily detected, and plasmon excitation can be controlled by the first detection means.
[0015]
Thereby, in the above configuration, since the plasmon excitation can be optimized by the first detection means, the optical information reproduction from the sample using the electromagnetic field by the plasmon excitation is further stabilized by the first detection means. it can.
[0016]
The optical device further includes a light amount of the light beam, a distance between the hemispherical lens and the plasmon portion, and a relative position between the light beam and the hemispherical lens based on an output signal of the first detection unit. It is preferable to include a control means for controlling at least one of the above.
[0017]
According to the above configuration, by providing the control means, the excited state of the plasmon part can always be optimally controlled, and stable optical information reproduction and / or recording can be performed.
[0018]
In the optical apparatus, the reproducing unit further detects a light component from the sample other than the light that has contributed to plasmon excitation in the light beam in order to reproduce the sample information. It is desirable to have
[0019]
According to the above configuration, even if the light amount of the light component involved in plasmon excitation is reduced, the optical information is stabilized from the sample by providing the second detection means for detecting the light component other than the light component. And the servo control for optimally controlling the position of the condenser lens and hemispherical lens to the information recording position of the sample based on the detection signal from the second detection means. .
[0020]
In the optical device, the second detection means is disposed at a position for detecting light at the center of the transmitted beam or the reflected beam, while the first detection means is provided at an outer peripheral portion with respect to the center. You may arrange | position in the position which detects light.
[0021]
According to the above configuration, with respect to the reflected light or transmitted light from the sample based on the irradiation of the light beam, the light component involved in plasmon excitation and the light component not involved are separated and detected signals (electric Plasmon excitation control and optical information reproduction can be performed independently and in synchronization with each other, so that the above control and reproduction can be performed more stably. .
[0022]
The optical apparatus may further include recording means for optically recording information on the sample by outputting a recording signal based on the recorded information to the irradiation means. According to the above configuration, since the recording unit is provided, high-sensitivity recording can be performed on the sample using an electromagnetic field generated by plasmon excitation of the plasmon portion by irradiation of the light beam from the irradiation unit.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of an optical disk device as an optical device according to the present invention will be described below with reference to FIGS.
[0024]
In the optical disk apparatus, as shown in FIGS. 1 and 2, a laser beam (light beam) 11 from a laser light source (not shown) is applied to an optical disk (sample) 14 for optically recording information, and a condenser lens 12 and A light irradiating unit 10 for entering through the hemispherical lens 13 and a reproducing circuit 19 for reproducing information by light from the optical disk 14 based on the laser beam 11 are provided. Therefore, the condenser lens 12 and the hemispherical lens 13 constitute an objective lens unit.
[0025]
In the optical disc 14, a recording layer 14a is provided on the surface facing the hemispherical lens 13 so as to include a plasmon excitation material as a plasmon part. As a result, the plasmon excitation material is disposed close to the optical disk 14 on the optical path of the laser beam 11 between the hemispherical lens 13 and the optical disk 14.
[0026]
The optical disk 14 is obtained by forming a recording layer 14a on a substrate 14b. The recording layer 14a includes an optical recording portion that can optically record information and a plasmon excitation material that is easily excited by laser light having a specific wavelength or light intensity.
[0027]
Examples of the optical recording unit include those using organic dyes, polymers, magneto-optical recording media, and the like that are denatured or melted by heating by laser or plasmon excitation. A magneto-optical recording medium can record information in each recording area in each direction of perpendicular magnetization, and also when a Kerr rotation angle changes due to a change in each direction of perpendicular magnetization when irradiated with coherent light such as laser light. Information can be reproduced.
[0028]
Specific examples of the organic dyes and polymers include cyanine dyes, merocyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, metal complexes thereof, squarylium dyes, dithiols, diazoles, mercaptonaphthols, and the like, condensed aromatics Quinone dyes, triphenylmethane dyes, aminium, diimmonium dyes, azo disperse dyes, indoaniline metal complex dyes, pigments, etc. are colored dyes, and methacrylic resins, acrylic resins, polyester resins, etc. are mentioned as the above polymers. be able to. Examples of the magneto-optical recording medium include rare earth transition metal thin films such as GdTbFe, TbFeCo, DyFeCo, and TbDyFeCo.
[0029]
In the present invention, in addition to the heating by the laser beam 11, the irradiation portion of the laser beam 11 in the recording layer 14a can be efficiently heated by the local heating by the plasmon excitation by the laser beam 11. Therefore, as the recording layer 14a, For example, by using a read magnetic layer that has in-plane magnetization at room temperature and changes to perpendicular magnetization as the temperature rises on a recording magnetic layer that records information by perpendicular magnetization, the read magnetic layer is used. Reading information from the layer can be improved.
[0030]
In the present invention, since the heating temperature of the reading portion in the recording layer 14a can be set large, the Curie temperature of the reading magnetic layer and the temperature changing to the perpendicular magnetization can be set high, so that the change in the Kerr rotation angle is greatly increased. In addition, the reproduction output from the reading magnet can be increased, and the reading of information from the recording layer 14a can be stabilized and ensured.
[0031]
The plasmon excitation material is not particularly limited as long as it generates plasmon vibration by plasmon resonance (plasma resonance) by laser light irradiation. For example, a metal, an alloy, a semiconductor, or an organic compound having free electrons may be used. Can be mentioned. Specific examples of the material include gold, silver, aluminum, and copper.
[0032]
Further, each material as the magneto-optical recording medium is an alloy and has high conductivity, and therefore has free electrons that excite plasmons. Therefore, the optical recording part and the plasmon excitation material can be used together. On the other hand, some organic dyes and polymers also have insulators. In that case, a plasmon excitation material may be deposited on the upper layer of the optical recording unit, that is, between the optical recording unit and the hemispherical lens 13 ( Not shown).
[0033]
The plasmon excitation material further increases the surface plasma mon excitation effect, enhances the interaction between the optical recording portion and the surface plasmon excitation effect, and effectively uses the absorbed laser energy. Therefore, when a polycrystalline material or the like is used, a fine particle shape with a particle size of 300 nm or less, more preferably a particle size of 100 nm or less is preferable.
[0034]
The hemispherical lens 13 is a convex lens called SIL (Solid Immersion Lens), and a condensing lens which is a convex lens by using the hemispherical lens 13 having a refractive index larger than air (refractive index is 1). 12, the wavelength of the light condensed on the recording layer 14a is set to be small, and the resolution of the light condensed on the recording layer 14a is improved. The hemispherical lens 13 includes a hemispherical lens as well as a super hemispherical lens. For convenience of explanation, only the hemispherical lens will be described in the present embodiment.
[0035]
The condensing lens 12 and the hemispherical lens 13 are arranged so that the central axes of the both coincide with the optical axis of the parallel light flux P1 incident on the condensing lens 12, respectively. The condensing lens 12 and the hemispherical lens 13 are provided along the traveling direction of the parallel light flux P1 incident on the condensing lens 12.
[0036]
In the hemispherical lens 13, the light incident surface is a hemispherical surface, and the light emitting surface is a flat surface (perpendicular to the central axis of the hemispherical lens 13). The hemispherical surface is set to be a part of a spherical surface centering on the focal point of the light collected by the condenser lens 12. In the present embodiment, the numerical aperture of the condenser lens 12 is NA, and the refractive index of the hemispherical lens 13 is N1 (> 1).
[0037]
In such an optical disc apparatus, the light (wavelength = λ) of the parallel light flux P1 incident on the condenser lens 12 is condensed by the condenser lens 12. The condensed light is incident on the hemispherical surface of the hemispherical lens 13 perpendicularly. This incident light becomes a luminous flux having a numerical aperture NA and a wavelength of λ / N1 in the hemispherical lens 13, and is emitted from the flat surface of the hemispherical lens 13 and once enters the atmosphere, and then enters the recording layer 14a. To do.
[0038]
Here, when the numerical aperture of the light emitted from the hemispherical lens 13 is increased in order to reduce the beam spot diameter collected on the recording layer 14a, the incident angle to the flat surface of the hemispherical lens 13 or the recording layer 14a. Therefore, reflection occurs on the surface of the recording layer 14a or on the flat surface of the hemispherical lens 13, resulting in a loss of light amount.
[0039]
Therefore, in the present invention, the gap 15 (the distance of the used laser beam wavelength λ or less, more preferably λ / 4 or less, for example, several tens of nm or less) is used to bring the flat surface of the hemispherical lens 13 close to the recording layer 14a. ), The hemispherical lens 13 is arranged with respect to the recording layer 14a. Such a gap 15 can be formed, for example, by rotating the optical disk 14 with respect to the hemispherical lens 13 and causing the hemispherical lens 13 to float on the recording layer 14a.
[0040]
By arranging in this manner, evanescent light as near-field light is transmitted from the total reflection surface on the flat surface of the hemispherical lens 13 to the adjacent recording layer 14a. That is, the light beam emitted from the flat surface of the hemispherical lens 13 is combined with the recording layer 14a by the near field effect and travels in substantially the same direction as the traveling direction in the hemispherical lens 13. For this reason, the condensed light beam can be guided to the recording layer 14a without causing large reflection when the hemispherical lens 13 is emitted into the atmosphere.
[0041]
At this time, the light beam guided to the recording layer 14 a has the same property as the light propagating in the hemispherical lens 13. For this reason, the light propagating to the recording layer 14a becomes a light flux having a numerical aperture NA and a wavelength λ / N1. Therefore, a light beam having a wavelength of λ / N1 and a numerical aperture NA is incident on the surface of the recording layer 14a.
[0042]
For this reason, the beam spot diameter of the laser beam 11 condensed on the recording layer 14a is set to 1 / N1 as compared with the normal case where the laser beam 11 is condensed on the recording layer 14a by the condenser lens 12. Therefore, the density of information that can be optically recorded in the recording layer 14 a can be further increased by the hemispherical lens 13.
[0043]
In the optical disk device, since the hemispherical lens 13 is provided, the recording layer 14a can be irradiated with a sufficient amount of light while suppressing reflection, so that information from the recording layer 14a can be further increased in density. Can be recorded and / or reproduced.
[0044]
Instead of the gap 15, a protective layer (not shown) having the same optical thickness is provided above the recording layer 14a, the bottom surface of the hemispherical lens 13, or both (in this case, the sum of the thicknesses). Is set to be the same as the gap 15.) The hemispherical lens 13 and the optical disk 14 may be brought into contact with each other through a protective layer. At this time, the refractive index of the protective layer is preferably set to be the same as the refractive index of the aforementioned hemispherical lens 13 as N1.
[0045]
As will be described later, in the laser beam 11, an optical component 11b having an outer ring shape is totally reflected by the recording layer 14a when plasmon resonance is not excited, while a circular optical component inside the optical component 11b. In 11a, transmission, absorption, and reflection occur depending on the optical characteristics of the recording layer 14a.
[0046]
Further, since the outer light component 11b can be set to have a wavelength and an incident angle that excite plasmon resonance in the recording layer 14a, the incident angle of the outer light component 11b to the hemispherical lens 13 is, for example, By adjusting the distance between the condensing lens 12 and the hemispherical lens 13, it is possible to set the light intensity to excite the plasmon resonance, and to excite the plasmon resonance appropriately and surely, so that the stronger near field Light can be generated.
[0047]
This incident angle changes depending on the distance between the condenser lens 12 and the hemispherical lens 13, for example. As shown in FIG. 3, when this distance becomes the distance x1 for exciting the plasmon, the light component 11b outside the laser beam is absorbed by the plasmon excitation in the recording layer 14a, and plasmon resonance occurs. This distance can be easily adjusted by the driving device of the condenser lens 12 in the optical axis direction.
[0048]
Further, the gap 15 between the recording layer 14a and the hemispherical lens 13 is adjusted to x2 as shown in FIG. 4, or the laser light output is adjusted to Po as shown in FIG. Thus, plasmon excitation in the recording layer 14a can be generated most appropriately.
[0049]
Thus, for plasmon excitation, light is preferably incident from an oblique direction, and the wavelength of incident light in the hemispherical lens 13 and the wave number for plasmon excitation need to match each other. From this, the plasmon excitation depends on the incident angle of the light from the hemispherical lens 13 and also on the wavelength of the light. Therefore, the plasmon excitation can be accurately determined by each setting of the incident angle and the wavelength of the light as described above. Are controlled by
[0050]
As shown in FIG. 1, the plasmon excitation part 14c excited in the recording layer 14a has an electromagnetic field strength several tens to several hundreds times that of normal near-field light. Optical information can be amplified or used as an electromagnetic field for recording. Further, the hemispherical lens 13 can set the excitation region to be extremely small.
[0051]
Therefore, strong near-field light is generated by generation of strong electromagnetic waves due to plasmon excitation, and the strong near-field light is directly involved in recording / reproduction in the recording layer 14a, as in the case of normal propagation light, After the field light interacts with the recording layer 14a and is converted into propagating light or heat, the recording layer 14a is involved in the recording / reproducing so that the recording layer 14a has high sensitivity (high S / N ratio) and high density optical information. Can be reproduced or recorded using the above-mentioned strong near-field light.
[0052]
In the above description, a plasmon excitation layer for exciting plasmons may be separately formed on the recording layer 14a to separate the electromagnetic field enhancement function from the recording and reproduction functions.
[0053]
When the plasmon excitation material is excited in the recording layer 14a, the outer light component 11b is absorbed by the plasmon excitation material of the recording layer 14a, and the reflected light from that portion decreases. Therefore, it is more practical to always reproduce the optical information from the recording layer 14a by the light component 11a inside the reflected light or transmitted light. Further, positioning of the laser beam 11 such as tracking servo is preferably performed based on the reflected light or transmitted light of the inner light component 11a.
[0054]
FIG. 6 is a diagram showing a detector for detecting the outer light component 11b and the inner light component 11a. The detector includes a photodetector having a circular center detector (second detector) 30a and an annular outer periphery detector (first detector) 30b so as to cover the outer periphery of the center detector 30a. Each has.
[0055]
If the center detector 30a is a quadrant detector further divided into ten characters, it can perform focus servo by the astigmatism method and track servo by the push-pull method.
[0056]
The outer periphery detection unit 30b is for detecting the light component of the incident angle that contributes to the plasmon excitation of the plasmon part by the laser beam 11 from the transmitted light or the reflected light from the optical disc 14.
[0057]
The center detector 30a receives the light component 11a inside the reflected light and converts it into an electric signal 31, and the outer periphery detector 30b receives the light component 11b outside the reflected light and converts it into an electric signal 32. As a result, the outer light component 11b and the other inner light component 11a that contributed to plasmon excitation in the laser beam 11 can be separated into each other and independently converted into electrical signals 32 and 31, respectively.
[0058]
The shapes of the center detector 30a and the outer periphery detector 30b, which are the photodetectors, are not limited to the circular shape or the annular shape described above, but three detectors arranged on a straight line, and the center detector detects the inner light component 11a. The two detectors on both sides may be configured to detect the outer light component 11b.
[0059]
FIG. 2 is a block diagram of an apparatus for recording / reproducing information on the optical disk 14. The recording signal emitted from the recording circuit 18 is sent to the laser driving circuit 17, and the laser beam 11 modulated by the recording signal emitted from a laser light source such as a semiconductor laser in the optical pickup 16 passes through the hemispherical lens 13. The information is recorded by irradiating the optical disc 14 via the optical disc 14.
[0060]
At the time of reproduction, the optical disk 14 is irradiated with a reproduction laser beam 11 having a light amount weaker than that at the time of recording. The reflected light from the optical disk 14 is converted into electrical signals 31 and 32 by the center detector 30a and the outer periphery detector 30b, which are photodetectors in the optical pickup 16. Of the reflected light, the electrical signal 31 from the inner light component 11a is sent to the reproducing circuit 19 and used for reproducing information.
[0061]
The electric signal 32 from the outer light component 11 b is sent to the signal processing circuit 24. In the signal processing circuit 24, the servo circuit 20, the laser driving circuit 17, and the like so that the reflected light amount becomes the minimum as shown in FIGS. 3 to 5 or the reflected light amount is lower than a preset threshold value. The rotation control circuit 25 is feedback controlled by the control signal 33.
[0062]
The servo circuit 20 drives the condenser lens 12 in the optical pickup 16. The laser drive circuit 17 adjusts the amount of light emitted from the semiconductor laser in the optical pickup 16. The rotation control circuit 25 controls the rotation speed of the optical disk 14 so that the distance between the hemispherical lens 13 and the optical disk 14, that is, the flying height of the air is appropriate.
[0063]
Further, in place of the optical disk 14 shown in FIG. 1, as shown in FIG. 7, a hemispherical lens 21 and a recording layer 22 a containing the plasmon excitation material described above are sandwiched with a substrate 22 b having optical transparency. The arranged optical disk 22 may be used. In this case, the sum of the thicknesses of the hemispherical lens 21 and the substrate 22b is the optical thickness of the aforementioned hemispherical hemispherical lens 13 (that is, the distance between the flat surface of the hemispherical lens 13 and the apex of the hemispherical surface). It is desirable that it is set to be equivalent to
[0064]
In such a configuration, since the hemispherical lens 21 slides on the optical disc 22 on the substrate 22b, the recording layer 22a is not damaged even if the sliding fails, that is, the substrate 22b is crashed due to the sliding. The plasmon excitation material contained therein can be excited semipermanently and stably as the plasmon excitation part 22c.
[0065]
Instead of the configuration shown in FIG. 1, a plasmon excitation layer 23 containing the plasmon excitation material described above may be formed on the bottom surface of the hemispherical lens 13 as shown in FIG. 8. The plasmon excitation layer 23 faces the optical disc 14 with a gap 15 therebetween. For example, the hemispherical lens 13 is floated on the optical disc 14 so that the gap 15 is several tens of nm or less, which is equal to or less than the wavelength λ of the used laser beam, more preferably λ / 4 or less. As a result, the near field 14d generated by condensing the laser beam 11 in the plasmon excitation part 14c of the plasmon excitation layer 23 reaches the recording layer 14a via the gap 15 and has the same effect as described above.
[0066]
Instead of the gap 15, a protective layer (not shown) having the same optical thickness is provided above the recording layer 14a, below the plasmon excitation layer 23, or both (in this case, the sum of the thicknesses). The hemispherical lens 13 and the optical disk 14 may be in contact with each other, that is, the hemispherical lens 13 may be set to slide on the protective layer.
[0067]
The outer light component 11b of the laser beam 11 excites the plasmon excitation layer 23, and the inner light component 11a passes through the plasmon excitation layer 23 and is transmitted, absorbed, and reflected by the optical characteristics of the recording layer 14a. In this case, since the recording layer 14a can be freely selected without considering plasmon excitation, it is possible to select another material that cannot excite plasmons.
[0068]
Further, by replacing the recording layer 14a with another observation sample and using, for example, a CCD as a photodetector, a high-sensitivity and high-resolution optical microscope can be realized as an optical device.
[0069]
By the way, conventionally, the generation of the near field is not limited to the use of plasmons. Usually, if there is a region (aperture) having a different refractive index smaller than the diffraction limit (several tens of nm), the near field is around it. Occurs. The electric field (which may be an electromagnetic field) at this time is very small, and the near-field optical microscope uses this, and thus has a disadvantage that the S / N ratio is low and it is difficult to obtain a clear image.
[0070]
On the other hand, in the present invention, since plasmons are used, a near field having an intensity of several tens to several hundreds of times can be generated compared to the above normal near field, using light from the strong near field, The S / N ratio can be increased and a clearer image can be obtained.
[0071]
【The invention's effect】
As described above, the optical apparatus according to the present invention includes an irradiating unit that focuses a light beam on a sample on which information to be optically reproduced is recorded by a condenser lens, and an optical path on the optical beam that reaches the sample. In addition, an electromagnetic field is generated by the irradiation of the light beam, and information is reproduced from the plasmon portion arranged close to the sample and light from the sample irradiated with the light beam by using the generation of the electromagnetic field. And a hemispherical lens for making the light beam from the condensing lens have a wavelength smaller than that when propagating in the air and making it incident on the plasmon part and the sample by the near-field effect. It is a configuration.
[0072]
Therefore, in the above configuration, by providing the plasmon part and the hemispherical lens on the optical path of the light beam from the condenser lens to the sample, the beam spot diameter can be set smaller by the hemispherical lens, and the plasmon By generating a strong electromagnetic field due to plasmon excitation of the part, it is possible to cope with an improvement in the recording density in the sample and to achieve more reliable and stable information reproduction from the sample.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an optical device of the present invention.
FIG. 2 is a block diagram for recording and reproducing information in the optical apparatus.
FIG. 3 is a graph for explaining a relationship between a distance between a condenser lens and a hemispherical lens for exciting a plasmon part in the optical device.
FIG. 4 is a graph for explaining a relationship between a distance between a recording layer for exciting a plasmon portion and a hemispherical lens in the optical device.
FIG. 5 is a graph illustrating the relationship between the amount of light emitted from a laser beam for exciting a plasmon part in the optical device.
FIG. 6 is a schematic plan view of a detector that detects an outer light component and an inner light component of reflected light in the optical device.
FIG. 7 is a schematic view showing another modification of the optical device.
FIG. 8 is a schematic view showing still another modification of the optical device.
[Explanation of symbols]
11 Light beam
12 Condensing lens
13 Hemispherical lens
14 Optical disc (sample)
14a Recording layer (sample)
14b substrate
30a Photodetector (second detection means)
30b Photodetector (first detection means)

Claims (5)

An irradiating means for condensing a light beam by a condenser lens and entering the sample for recording information to be optically reproduced,
A plasmon part that is generated in the vicinity of the sample by generating an electromagnetic field by irradiation of the light beam on the optical path to the sample in the light beam;
Reproducing means for reproducing information from the light from the sample irradiated with the light beam using generation of the electromagnetic field;
A hemispherical lens for making the light beam from the condensing lens have a wavelength smaller than that when propagating in the air and entering the plasmon part and the sample by a near-field effect ;
An optical apparatus , further comprising first detection means for detecting a light component contributing to plasmon excitation in the light from the sample . Based on the output signal of the first detection means, in order to control plasmon excitation, the light amount of the light beam, the distance between the hemispherical lens and the plasmon excitation material, or the light beam and the hemispherical lens 2. The optical apparatus according to claim 1, further comprising control means for controlling at least one of the relative positions. The reproducing means includes second detecting means for detecting a light component from the sample other than the light beam that contributed to plasmon excitation in the light beam in order to reproduce the information of the sample. The optical device according to claim 1 or 2 . The second detection means is arranged at a position for detecting light at the central portion of the transmitted beam or reflected beam from the sample, while the first detection means is arranged at the outer peripheral portion with respect to the central portion from the sample. 4. The optical apparatus according to claim 3 , wherein the optical apparatus is disposed at a position for detecting light. By outputting the recording signal based on the recording information to the irradiation unit, wherein to the sample, either 4 claims 1, characterized in that it comprises a recording means for recording information optically The optical device according to one.

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