JP4265941B2 - Optical head device and optical information recording / reproducing device - Google Patents

Description

【００２５】
次に本発明に係る光学ヘッド装置の別の実施例について説明する。
図３は本発明の別の実施例を示す光学ヘッド装置の斜視図である。この光学ヘッド装置においては、光学ガラス等の透明な材料からなり直方体状で光学的に平坦な基板３１の平面（図では右側面）に金属膜３２が形成されている。基板３１としては図１に示した実施例と同様に石英やポリカーボネート等を用いることができる。また、金属膜３２としてはＡｕ、Ａｇ、Ａｌなどの金属を用いることができ、この金属膜３２上に周期的な微細構造３３が形成されている。尚、周期的な微細構造の詳細な構造は図２に示した実施例と同様であるので、ここでは説明を省略する。
【００２６】
次に本発明の光学ヘッド装置を用いた光学情報記録再生装置について説明する。図４は本発明の一実施例を示す光学情報記録再生装置の概略構成図であり、この光学情報記録再生装置においては、図１に示した構造を持つ光学ヘッド装置４２から近接場光を記録媒体４７に照射する。光学ヘッド装置４２はスライダ状に形成されホルダ４３に支持され、回転する記録媒体４７上を走引される。記録媒体４７は表面保護層４４、記録層４５、下地層４６を備え、表面保護層４４によりスライダ部との磨耗に耐えるように構成されている。
【００２７】
図４において、レーザー光源４１から照射された光はコリメータレンズ（図示せず）により平行光束に変換され図１に示した構造を持つ光学ヘッド装置４２に入射する。この時、光学ヘッド装置４２に形成された金属膜（図１の金属膜１２）に対してｐ偏光になるように入射光を制御する必要がある。光学ヘッド装置４２に入射した光は金属膜界面で表面プラズモンを発生し、光学ヘッド装置４２に形成された周期的な微細構造により、プラズモンを既定の焦点に集中させ、光学ヘッド装置４２より近接場光を発生させる。光学ヘッド装置４２と記録媒体４７が照射光の波長より十分近接している時、発生した近接場光は記録媒体４７に結合し、記録層４５に記録マークを形成する。
【００２８】
また、再生の場合は、記録媒体４７を透過する近接場光成分が対物レンズ４８により平行光束に変換され、結像レンズ４９で光検出器５０上にスポットを結ぶ。この光検出器５０上の光強度の明暗により、記録媒体４７上に記録された情報を再生することができる。また、光学ヘッド装置４２から反射してきた光束を光検出器５１で検出することで、発生した近接場光の記録媒体４７の記録マークと未記録部分との反射率の差を検出することでも、記録媒体４７上に記録された情報を再生することができる。
【００２９】
前述したように記録媒体４７は表面保護層４４、記録層４５、記録層の下基板側に下地層４６を備え、表面保護層４４により光学ヘッド装置４２との磨耗に耐えるように構成されている。基板としては、ガラス、プラスチック又は高分子化合物などが使用可能であり、例えばポリカーボネートを射出成形してディスク基板を作製することが可能である。基板上の記録媒体の最表面は近接場光プローブを構成する光学ヘッド装置４２と波長以下の距離に近づいて高速に走引するため、記録層４５の磨耗を防ぐための保護層４４が必要である。この保護層４４としては、厚みが薄く、光の吸収がほとんどない材料が望ましい。
【００３０】
本発明では上記条件を満足する材料として、記録媒体４７の最表面の保護層４４にダイアモンドライクカーボンからなる保護膜を用いた。この保護膜の形成はスパッタリング、イオンビームスパッタリングやＣＶＤ（Chemical Vapor Deposition）法などの成膜装置で可能である。本実施例では最表面保護膜としてダイヤモンドライクカーボンをＣＶＤ法により作製した。また、保護層４４としてはＳｉＮを使用することも可能である。このＳｉＮ保護層もスパッタリング、イオンビームスパッタリングやＣＶＤ法などの成膜装置で形成することが可能である。保護層４４としては、近接場光はプローブからの染み出しが波長以下であるため、記録層４５までの距離をできるだけ近づけるために、厚みが薄く、光の吸収がほとんどない材料が望ましい。
【００３１】
記録層４５としては、公知の各種記録材料を用いて形成することができるが、とくに四元系相変化光記録材料（例えばＡｇＩｎＳｂＴｅ系）が好ましい。記録層４５の形成方法は、それぞれの材料に応じた公知の形成方法を採用することができる。また、記録層４５がＡｇＩｎＳｂＴｅのように蒸発性を持つ場合には、その上に、またはその上下に保護層、例えば、ＺｎＳ・ＳｉＯ_２層を設けることが好ましい。この保護層は記録層の酸化防止、熱伝導性の向上、記録時における記録材料の蒸発防止などの役割を果たしている。基板４７としては、例えばプラスチック又は高分子化合物、化学強化ガラス（アルミノシリケート系ガラスなど）、石英ガラスなどがあり、その厚みは通常０．５〜１．５ｍｍ、好ましくは０．６〜１．２ｍｍである。
【００３２】
図４中に示したレーザー光源４１は直線偏光であることが好ましく、直線偏光は偏光板を挿入してもよいが、レーザーダイオード（ＬＤ：半導体レーザー）などはそれ自体直線偏光をもっているので、そのまま、または偏光板と組合せて直線偏光を発生させることができる。
【００３３】
次に図５は本発明の別の実施例を示す光学情報記録再生装置の概略構成図であり、この光学情報記録再生装置においては、図３に示した構造を持つ光学ヘッド装置４２’を用いて近接場光を記録媒体４７に照射する。尚、図５において図４と同符号を付けたものは同様の構成部材である。光学ヘッド装置４２’はスライダ状に形成されホルダ４３に支持され、回転する記録媒体４７上を走引される。記録媒体４７は、前述したように表面保護層４４、記録層４５、下地層４６を備え、表面保護層４４によりスライダ部との磨耗に耐えるように構成されている。
【００３４】
図５において、レーザー光源４１から照射された光はコリメータレンズ（図示せず）により平行光束に変換され図３に示した構造を持つ光学ヘッド装置４２’に入射する。この時、光学ヘッド装置４２’に形成された金属膜（図３の金属膜３２）に対してｐ偏光になるように入射光を制御する必要がある。光学ヘッド装置４２’に入射した光は金属膜界面で表面プラズモンを発生し、光学ヘッド装置４２’に形成された周期的な微細構造により、プラズモンを既定の焦点に集中させ、光学ヘッド装置４２’より近接場光を発生させる。光学ヘッド装置４２’と記録媒体４７が照射光の波長より十分近接している時、発生した近接場光は記録媒体４７に結合し、記録層４５に記録マークを形成する。
【００３５】
また、再生の場合は、記録媒体４７を透過する近接場光成分が対物レンズ４８により平行光束に変換され、結像レンズ４９で光検出器５０上にスポットを結ぶ。この光検出器５０上の光強度の明暗により、記録媒体４７上に記録された情報を再生することができる。また、光学ヘッド装置４２’から反射してきた光束をミラー５２を介して光検出器５１で検出することで、発生した近接場光の記録媒体４７の記録マークと未記録部分との反射率の差を検出することでも、記録媒体４７上に記録された情報を再生することができる。
【００３６】
【発明の効果】
以上説明したように、本発明に係る光学ヘッド装置では、光学的に平坦な基板に形成された平面（上面または下面、あるいは側面などの端面）に金属膜を有し、前記平面と該平面に入射する光軸とのなす角度が、前記金属膜に表面プラズモンの励起される角度であり、前記金属膜上に周期的な微細構造を持つため、高効率かつ安定に近接場光を発生させることができる。
【００３７】
すなわち請求項１に係る光学ヘッド装置では、光学的に平坦な基板に形成された平面に金属膜を有し、前記平面と該平面に入射する光軸とのなす角度が、前記金属膜に表面プラズモンの励起される角度であり、前記金属膜上に周期的な微細構造を持ち、この周期構造がプラズモンの集光点を原点として、入射プラズモンの波数をｋ、プラズモンの入射方向と原点とｎ番目の微細構造のなす角をαｎとしたとき、ｎ番目の微細構造が半径Ｒ上の円弧状に、
ｋＲ−ｋＲcosαｎ＝２πｎ
なる関係を満たす位置に配置されているため、散乱されたプラズモンの位相を効率よく集光点で揃えることができるため、高効率かつ安定に近接場光を発生させることができる。
【００３８】
請求項２に係る光学ヘッド装置では、光学的に平坦な基板に形成された平面に金属膜を有し、前記平面と該平面に入射する光軸とのなす角度が、前記金属膜に表面プラズモンの励起される角度であり、前記金属膜上に周期的な微細構造を持ち、この周期構造がプラズモンの集光点を原点として、入射プラズモンの波数をｋとすると、ｎ番目の微細構造が半径Ｒ上の円弧状に、
ｋＲ−ｋＲcosαｎ＝２πｎ
かつ、
αｎ＜４５度
なる関係を満たす位置に配置されてされているため、散乱されたプラズモンの位相を効率よく集光点で揃えることができるため、高効率かつ安定に近接場光を発生させることができる。
【００３９】
請求項３に係る光学ヘッド装置では、請求項１または２の構成及び効果に加え、前記金属膜がＡｇ、Ａｕ、Ａｌからなるため、安定かつ高効率に表面プラズモンを発生でき、その結果、高効率かつ安定に近接場光を発生させることができる。
【００４０】
請求項４に係る光情報記録再生装置では、記録媒体に近接して保持した光学ヘッド装置より発生する近接場光により所望の情報を前記記録媒体に記録または再生する光情報記録再生装置において、前記光学ヘッド装置に、請求項１〜３のいずれか一つに記載の光学ヘッド装置を用いたことにより、光利用効率が高く、良好な記録マークの形成ができ、高Ｓ／Ｎ比での信号の再生が可能になる。
また、請求項５に係る光情報記録装置では、請求項４の構成に加え、光源として、半導体レーザーを用いることにより、偏光子等を用いることなく、直線偏光を出射することが可能であるため、安価に、微細な記録マークを高密度、高効率かつ安定に記録・再生することができる。
【００４１】
請求項６に係る光情報記録再生装置では、請求項４または５の構成に加え、前記光学ヘッド装置に設けた金属膜に入射する光の偏光方向が、該金属膜に対してｐ偏光となることにより、高効率にプラズモンを発生可能であり、高効率かつ安定に近接場光を発生させることができ、光利用効率が高く、良好な記録マークの形成ができ、高Ｓ／Ｎ比での信号の再生が可能になる。
また、請求項７に係る光情報記録再生装置では、請求項４，５または６の構成に加え、前記記録媒体の基板がプラスチックまたは高分子化合物からなることにより、大量生産可能であり、より安価に光情報記録装置を構成することが可能になる。
【００４２】
請求項８に係る光情報記録再生装置では、請求項４〜７のいずれかの構成に加え、前記記録媒体の記録層に、ＡｇＩｎＳｂＴｅからなる記録層を用いたことにより、良好な微小記録マークを安定に形成することが可能になる。
また、請求項９に係る光情報記録再生装置では、請求項４〜８のいずれかの構成に加え、前記記録媒体の最表面に、ダイヤモンドライクカーボンが形成されていることにより、表面の磨耗に強く高信頼性で情報の記録・再生を行うことが可能になる。
さらに請求項１０に係る光情報記録再生装置では、請求項４〜８のいずれかの構成に加え、前記記録媒体の最表面にＳｉＮが形成されていることにより、表面の磨耗に強く高信頼性で情報の記録・再生を行うことが可能になる。
【図面の簡単な説明】
【図１】本発明の一実施例を示す光学ヘッド装置の斜視図である。
【図２】図１に示す光学ヘッド装置の金属膜に形成される微細構造の配置例を示す図である。
【図３】本発明の別の実施例を示す光学ヘッド装置の斜視図である。
【図４】本発明の一実施例を示す光学情報記録再生装置の概略構成図である。
【図５】本発明の別の実施例を示す光学情報記録再生装置の概略構成図である。
【符号の説明】
１１，３１：基板
１２，３２：金属膜
１３，３３：周期的な微細構造
４１：レーザー光源
４２，４２’：光学ヘッド装置
４３：ホルダ
４４：保護層
４５：記録層
４６：下地層
４７：記録媒体
４８：対物レンズ
４９：結像レンズ
５０：光検出器
５１：光検出器
５２：ミラー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical head device that generates near-field light with high efficiency using the surface plasmon effect, and an optical information recording / reproducing device that records and reproduces data at an ultra-high density using the optical head device. It is.
[0002]
[Prior art]
In recent years, with the development of the multimedia era in which various types of information such as audio and video moving image files and text files are combined, the recording and storing of a large amount of information that can quickly process and store a large amount of information A medium is essential. In the future, when high-definition moving images that are expected to become more widespread and bidirectional image communication such as VOD (Video-On-Demand) are realized, the required information recording medium And the capacity of the storage medium will be further increased. Under such circumstances, many recording and reproducing methods have been proposed at present. One of such data recording and reproducing methods is a method of recording and reproducing on a recording medium using light.
[0003]
A typical example of a recording method using light is a method using a local refractive index change by irradiating a specific polymer material with predetermined light to change its molecular structure, Amorphous alloy thin film made of transition metal is irradiated with light in a predetermined magnetic field and locally heated above the Curie point or compensation point to change the local magnetization direction. There are those that reversibly change the structure between crystal and amorphous by obtaining an amorphous phase by gradually cooling from a temperature higher than the crystallization transition point by heating to a low temperature and then rapidly cooling. . However, since these methods irradiate the recording medium with the laser light condensed by the lens optical system, the spot diameter of the laser light is an important parameter for determining the size of the recording mark. That is, the smaller the laser beam spot size, the more information can be recorded on the optical recording medium and the higher the recording density. For this purpose, it is only necessary to shorten the wavelength of the laser light and increase the numerical aperture (NA) of the objective lens of the optical pickup (optical head device).
[0004]
However, the size of the laser beam spot that can be reduced by shortening the wavelength of the laser beam and increasing the numerical aperture of the objective lens is about the wavelength of the laser beam. For example, in order to shorten the wavelength of the laser beam, a blue semiconductor laser (up to 400 nm) is used as the DVD light source instead of a red semiconductor laser (up to 660 nm) which is currently used as a light source of a DVD (digital versatile disk). When used, the recordable information amount per unit area of the DVD can be improved by about 2.5 times the information amount of the recording medium when a red semiconductor laser is used. However, in such a method, the spot diameter of light is limited by the light diffraction limit, and there is a limit to improving the recording density of the recording medium.
[0005]
Therefore, in view of the above-described problems, near-field optics or volume holograms are used as techniques based on a completely different principle from the prior art when processing a terabyte (TB) terabyte amount of information. Ultra-high density recording methods such as photo-chemical hole burning and three-dimensional optical recording have been proposed. However, the volume hologram and the photochemical hole burning have a drawback that it is difficult to put into practical use because there are significant restrictions on the usage environment of the recording medium.
[0006]
In general, from the light diffraction theory, the size (major axis) of the light focusing spot is determined by the light source wavelength and the numerical aperture (NA) of the lens, and the recording density of the recording medium depends on the degree of reduction of the size of the light focusing spot. The upper limit of is determined. Furthermore, the light diffraction phenomenon has the property that the beam becomes wider as the size of the light beam is reduced using a lens.
θ-λ / d (i)
It becomes. In the equation, θ represents the diffraction angle, d represents the beam diameter, and λ represents the wavelength of light. Therefore, as the beam size is reduced using the lens, the diffraction angle increases and the beam size cannot be reduced below a predetermined value.
[0007]
The recording density limit of optical recording media is
d to 1.22λ / NA (ii)
It is determined by the diffraction theory of light expressed approximately. Here, NA represents the numerical aperture of the objective lens. That is, the shorter the wavelength (λ) of the laser beam and the larger the numerical aperture (NA) of the lens, the smaller the size of the focused beam, and the recording surface density of the recording medium is the size of the spot. Due to the diffraction phenomenon due to the wave nature of light, the minimum size of information that can be recorded and reproduced per bit is approximately the wavelength of light. Therefore, in such a conventional technique, a method of shortening the wavelength of light, reducing the size of the focused light spot using a lens having a large numerical aperture, and increasing the recording density is used. The recording density obtained by the method is 20-30 Gbit / inch. ² Is expected to be the limit. That is, in the conventional system, since light is used as an electromagnetic wave, when the recording density is improved, there is a problem that a restriction due to a diffraction limit cannot be avoided.
[0008]
Therefore, in order to overcome such a diffraction limit, a method has been proposed in which light existing in the near field in the near field region (distance below the light wavelength from the surface of the substance) is used as a light source for the recording medium. In other words, since near-field light generated from an aperture smaller than the wavelength of light is not emitted in principle, information is recorded on a recording medium by using this near-field light interacting with a material located near the aperture. Further, by performing reproduction, there is a possibility that the diffraction limit can be overcome and the recording density of the conventional optical recording can be dramatically improved.
[0009]
To solve these problems, planar array probes have been proposed (see Patent Documents 1 and 2). In this method, minute openings are formed in an array on the same substrate by anisotropic etching of the silicon substrate. Therefore, there are many probes in one element, and the sweep speed of the element itself does not need to be so high. The recording medium is arranged so as to rotate with respect to the probes arranged in a grid pattern, and the probes arranged on the two-dimensional plane pass through different points on the recording medium.
[0010]
In addition, these planar aperture probes have produced minute apertures by digging a Si substrate by anisotropic etching. In this case, the part where the laser beam passes through the probe is a cavity, and when a more efficient light output (that is, for faster optical writing and reading) is required, this cavity part is closed. It was necessary to fill with a material having a high refractive index and a high confinement effect. In addition, a probe in which pyramidal silicon is formed to efficiently generate near-field light has been proposed (see Patent Document 3). In the present invention, a near-field optical probe having a pyramidal silicon protrusion on a glass substrate is proposed. The pyramidal silicon protrusions are formed by wet etching with an etching solution made of KOH and IPA (isopropyl alcohol).
[0011]
Further, in the structure of the near-field optical probe that emits the near-field light, a frustoconical protrusion made of a high refractive index material is formed on a transparent substrate. There has been proposed a near-field optical probe in which a frustum-shaped projection made of a refractive index material is formed by dry etching (see Patent Document 4). Since this near-field optical probe has good dimensional controllability and a high refractive index, it has excellent reachability of light emitted from a minute aperture.
[0012]
Furthermore, in order to further increase the efficiency of generating near-field light, an information recording / reproducing apparatus using surface plasmons has been proposed (see Patent Document 5). In this case, a total reflection surface is formed on the bottom surface of the triangular prism, and a mask surface having a minute opening for generating a near field is provided on the total reflection surface. In addition, the end face of the optical waveguide or optical fiber is cut obliquely, a metal film is formed on the end face, a pinhole is formed in the metal film, and the surface plasmon in the metal film is used to Light with improved transmittance (see Patent Document 6) or light that is incident on a flat substrate embedded with a minute metal, excites localized plasmons, and locally enhances the photoelectric field near the minute body. A method for recording and reproducing information in a minute area (see Patent Document 7) has been proposed. Non-Patent Document 1 (experimental study of surface plasmon scattering by individual surface defects) proposes examples of plasmon mirrors and plasmon lenses for controlling various surface plasmons by the surface structure.
[0013]
[Patent Document 1]
Japanese Patent No. 303085
[Patent Document 2]
JP-A-11-191238
[Patent Document 3]
JP 2001-208672 A
[Patent Document 4]
JP 2002-340773 A
[Patent Document 5]
JP 2000-132861 A
[Patent Document 6]
JP 2000-173093 A
[Patent Document 7]
JP 2001-256664 A
[Non-Patent Document 1]
IISmolyaninov et al., “Experimental study of surface-plasmon scattering by individual surface defects”, Physical Review B, Vol. 56, No. 3, pp. 1601-1611 (1997)
[0014]
[Problems to be solved by the invention]
In any of the methods described so far, in order to efficiently generate near-field light, a minute opening is made of a photorefractive index medium, or near-field light is efficiently generated using surface plasmons. However, in order to read and write information at higher density and at higher speed, and to use near-field light for nano-optical processing, optical communication, etc., it is necessary to realize a probe that generates near-field light with higher efficiency.
[0015]
The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical head device having a configuration capable of efficiently generating near-field light from a near-field probe portion by efficiently using surface plasmons. And Another object of the present invention is to provide an optical information recording / reproducing apparatus capable of recording / reproducing information with high efficiency and high speed by using the optical head device.
[0016]
[Means for Solving the Problems]
As means for achieving the above object, an optical head device according to the present invention comprises: ,light A metal film on a plane formed on a chemically flat substrate, and an angle between the plane and an optical axis incident on the plane is an angle at which surface plasmon is excited on the metal film, The film has a periodic fine structure, and this periodic structure has the plasmon focusing point as the origin, the wave number of the incident plasmon as k, and the angle between the incident direction of the plasmon and the origin and the nth fine structure as αn. When the nth microstructure is arcuate on the radius R,
kR-kRcosαn = 2πn
It is arranged at a position satisfying the following relationship (claims) 1 ).
In the optical head device according to the present invention, the metal film is provided on a plane formed on an optically flat substrate, and an angle formed between the plane and an optical axis incident on the plane is the metal film. This is the angle at which surface plasmons are excited, and has a periodic fine structure on the metal film. Plasmonic When the focal point is the origin and the wave number of the incident plasmon is k, the nth fine structure has an arc shape on the radius R,
kR-kRcosαn = 2πn
And
αn <45 degrees
It is arranged at a position satisfying the following relationship (claims) 2 ).
Furthermore, in the optical head device according to the present invention, the metal film is made of a metal such as silver (Ag), gold (Au), or aluminum (Al). 3 ).
[0017]
The present invention relates to an optical information recording / reproducing apparatus that records or reproduces desired information on the recording medium by near-field light generated from an optical head apparatus held close to the recording medium. ~ 3 The optical head device according to any one of the above is used. (Claim 4) .
In the optical information recording / reproducing apparatus according to the present invention, a semiconductor laser is used as the light source. 5 ).
Further, in the optical information recording / reproducing apparatus according to the present invention, the polarization direction of the light incident on the metal film provided in the optical head device is in the metal film. For p-polarized light (Claims) 6 ).
Furthermore, in the optical information recording / reproducing apparatus according to the present invention, the substrate of the recording medium is made of plastic or a polymer compound. 7 ).
In the optical information recording / reproducing apparatus according to the present invention, a recording layer made of AgInSbTe is used as the recording layer of the recording medium. 8 ).
Furthermore, in the optical information recording / reproducing apparatus according to the present invention, diamond-like carbon is formed on the outermost surface of the recording medium. 9 ).
In the optical information recording / reproducing apparatus according to the present invention, SiN is formed on the outermost surface of the recording medium. 10 ).
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration, operation and action of the present invention will be described in detail with reference to the drawings.
First, an optical head device according to the present invention will be described. FIG. 1 is a perspective view of an optical head device showing an embodiment of the present invention. In this optical head device, a metal film 12 is formed on a plane (upper surface in the drawing) of a substrate 11 made of a transparent material such as optical glass and having a rectangular parallelepiped shape and optically flat. As the substrate 11, quartz, polycarbonate, or the like can be used. The metal film 12 can be made of a metal such as silver (Ag), gold (Au), or aluminum (Al). A periodic fine structure 13 is formed on the metal film 12. The periodic fine structure may be a small dent or a bulge, and uses a focused ion beam, an atomic force microscope, a tunnel microscope, or the like. Can be processed. When forming the Ag or Au metal film, if the substrate 11 is made of quartz, the adhesion is improved by applying a chromium (Cr) base film of about several nm.
[0019]
Incident light to the optical head device is incident at a specific incident angle from the side of the substrate 11 where the metal film 12 is not formed. When p-polarized light is applied to the metal film 12 and the incident angle satisfies a certain condition, surface plasmons can be excited at the interface between the metal film 12 and the outer space. For example, when the material of the metal film 12 is Ag and the wavelength λ of incident light in vacuum is 633 nm, the refractive index n of the metal film 12 is 0.065-4.0i. The upper surface of the metal film 12 is air, and its refractive index is about 1.0. In this case, the propagation constant (wave number) k of the surface plasmon excited on the surface of the metal film 12 is the propagation constant k0 of the incident light,
k0 = 2π / λ
As
k = n / √ (n2 + 1) × k0 (1)
Given in.
[0020]
Here, when the material of the metal film 12 is Ag, the substrate 11 is quartz, and the refractive index nf is 1.457, the surface plasmon can be excited at an angle θ of about 45.1 degrees. This method is the excitation of surface plasmons by the so-called Kretschmann arrangement. In addition to Ag, the angle θ is, for example, 46.2 degrees for Au and 43.9 degrees for Al. This time, an Ag thin film deposited by 80 nm was used.
[0021]
The generated surface plasmon is scattered by the periodic fine structure 13 formed on the metal film 12, but if an appropriate structure is formed, it is possible to form a plasmon lens in which plasmons are concentrated at a point having a certain focal length. is there. By arranging a scattering source at this concentrated point, the plasmon is converted into near-field light, and can be used as a near-field light probe with higher efficiency than conventional.
[0022]
FIG. 2 shows an arrangement example of the above-described periodic fine structure. Here, the spherical fine structure 13 is arranged in an arc shape on the radius R with the condensing point as the origin. Here, αn is an angle formed by the y-axis and the nth spherical microstructure on the radius R. In FIG. 2, when surface plasmons propagate from the y-axis + ∞ direction, plasmons that are scattered by each spherical fine structure are superposed in the same phase on the origin to obtain plasmons enhanced than usual. be able to. Further enhanced near-field light can be obtained by arranging a fine structure as a scattering source at the origin.
[0023]
Here, when the periodic structure has the focal point as the origin and the wave number of the incident plasmon is k, when the nth fine structure is arranged in an arc shape on the radius R in the relationship of the following expression (2), A plasmon lens in which plasmons concentrate can be formed.
kR-kRcosαn = 2πn (2)
Table 1 below shows an arrangement example of the fine structure of the n-th surface with respect to each incident wavelength. Table 1 shows the arrangement of the left half of the microstructure with respect to the y-axis. However, as shown in FIG. 2, the microstructure is also arranged at a position symmetrical to the y-axis on the right side of the y-axis.
In the example shown here, the radius R is set to 5 μm. This radius R needs to be set to be equal to or less than the propagation length of plasmon. Since the propagation length here was 9.1 μm, the radius was 5 μm. Further, the angle α formed by the nth microstructure and the y-axis is desirably 45 degrees or less (αn <45 degrees) as shown in FIG.
[0024]
[Table 1]

[0025]
Next, another embodiment of the optical head device according to the present invention will be described.
FIG. 3 is a perspective view of an optical head device showing another embodiment of the present invention. In this optical head device, a metal film 32 is formed on a plane (right side in the drawing) of a substrate 31 made of a transparent material such as optical glass and having a rectangular parallelepiped shape and optically flat. As the substrate 31, quartz, polycarbonate or the like can be used as in the embodiment shown in FIG. Further, a metal such as Au, Ag, or Al can be used as the metal film 32, and a periodic fine structure 33 is formed on the metal film 32. The detailed structure of the periodic fine structure is the same as that of the embodiment shown in FIG.
[0026]
Next, an optical information recording / reproducing apparatus using the optical head device of the present invention will be described. FIG. 4 is a schematic configuration diagram of an optical information recording / reproducing apparatus showing an embodiment of the present invention. In this optical information recording / reproducing apparatus, near-field light is recorded from the optical head device 42 having the structure shown in FIG. The medium 47 is irradiated. The optical head device 42 is formed in a slider shape, is supported by a holder 43, and runs on a rotating recording medium 47. The recording medium 47 includes a surface protective layer 44, a recording layer 45, and an underlayer 46, and is configured to withstand abrasion with the slider portion by the surface protective layer 44.
[0027]
In FIG. 4, light emitted from a laser light source 41 is converted into a parallel light beam by a collimator lens (not shown), and enters an optical head device 42 having the structure shown in FIG. At this time, it is necessary to control the incident light so as to be p-polarized with respect to the metal film (metal film 12 in FIG. 1) formed on the optical head device 42. The light incident on the optical head device 42 generates surface plasmons at the metal film interface, and the periodic fine structure formed in the optical head device 42 concentrates the plasmons at a predetermined focal point. Generate light. When the optical head device 42 and the recording medium 47 are sufficiently closer than the wavelength of the irradiation light, the generated near-field light is coupled to the recording medium 47 and forms a recording mark on the recording layer 45.
[0028]
In the case of reproduction, the near-field light component transmitted through the recording medium 47 is converted into a parallel light beam by the objective lens 48 and a spot is formed on the photodetector 50 by the imaging lens 49. The information recorded on the recording medium 47 can be reproduced by the brightness of the light intensity on the photodetector 50. Further, by detecting the light beam reflected from the optical head device 42 with the photodetector 51, it is possible to detect the difference in reflectance between the recorded mark of the recording medium 47 and the unrecorded portion of the generated near-field light, Information recorded on the recording medium 47 can be reproduced.
[0029]
As described above, the recording medium 47 includes the surface protective layer 44, the recording layer 45, and the base layer 46 on the lower substrate side of the recording layer, and the surface protective layer 44 is configured to withstand abrasion with the optical head device 42. . As the substrate, glass, plastic, a polymer compound, or the like can be used. For example, a disk substrate can be manufactured by injection molding polycarbonate. Since the outermost surface of the recording medium on the substrate approaches the optical head device 42 constituting the near-field optical probe at a distance shorter than the wavelength and runs at a high speed, a protective layer 44 for preventing the recording layer 45 from being worn is necessary. is there. The protective layer 44 is preferably made of a material that is thin and hardly absorbs light.
[0030]
In the present invention, as a material satisfying the above conditions, a protective film made of diamond-like carbon is used for the protective layer 44 on the outermost surface of the recording medium 47. This protective film can be formed by a film forming apparatus such as sputtering, ion beam sputtering or CVD (Chemical Vapor Deposition). In this example, diamond-like carbon was produced by CVD as the outermost surface protective film. Further, SiN can be used as the protective layer 44. This SiN protective layer can also be formed by a film forming apparatus such as sputtering, ion beam sputtering or CVD. As the protective layer 44, since the near-field light oozes from the probe at a wavelength or less, a material that is thin and hardly absorbs light is desirable in order to make the distance to the recording layer 45 as close as possible.
[0031]
The recording layer 45 can be formed using various known recording materials, and a quaternary phase change optical recording material (for example, AgInSbTe system) is particularly preferable. As the forming method of the recording layer 45, a known forming method corresponding to each material can be adopted. Further, when the recording layer 45 is evaporative like AgInSbTe, a protective layer, for example, ZnS · SiO is formed on or above it. ₂ It is preferable to provide a layer. This protective layer plays the role of preventing oxidation of the recording layer, improving thermal conductivity, and preventing evaporation of the recording material during recording. Examples of the substrate 47 include plastics or polymer compounds, chemically tempered glass (such as aluminosilicate glass), and quartz glass. The thickness is usually 0.5 to 1.5 mm, preferably 0.6 to 1.2 mm. It is.
[0032]
The laser light source 41 shown in FIG. 4 is preferably linearly polarized light, and linearly polarized light may have a polarizing plate inserted therein, but a laser diode (LD: semiconductor laser) or the like itself has linearly polarized light, so that Alternatively, linearly polarized light can be generated in combination with a polarizing plate.
[0033]
Next, FIG. 5 is a schematic configuration diagram of an optical information recording / reproducing apparatus showing another embodiment of the present invention. In this optical information recording / reproducing apparatus, an optical head device 42 ′ having the structure shown in FIG. 3 is used. Then, the near-field light is irradiated to the recording medium 47. In FIG. 5, the same reference numerals as those in FIG. 4 denote the same constituent members. The optical head device 42 ′ is formed in a slider shape, supported by a holder 43, and traversed on a rotating recording medium 47. As described above, the recording medium 47 includes the surface protective layer 44, the recording layer 45, and the base layer 46, and is configured to withstand abrasion with the slider portion by the surface protective layer 44.
[0034]
In FIG. 5, the light emitted from the laser light source 41 is converted into a parallel light beam by a collimator lens (not shown) and enters an optical head device 42 ′ having the structure shown in FIG. At this time, it is necessary to control the incident light so as to be p-polarized with respect to the metal film (metal film 32 in FIG. 3) formed on the optical head device 42 ′. The light incident on the optical head device 42 ′ generates surface plasmons at the metal film interface, and the plasmons are concentrated on a predetermined focal point by the periodic fine structure formed on the optical head device 42 ′. More near-field light is generated. When the optical head device 42 ′ and the recording medium 47 are sufficiently close to the wavelength of the irradiation light, the generated near-field light is coupled to the recording medium 47 and forms a recording mark on the recording layer 45.
[0035]
In the case of reproduction, the near-field light component transmitted through the recording medium 47 is converted into a parallel light beam by the objective lens 48 and a spot is formed on the photodetector 50 by the imaging lens 49. The information recorded on the recording medium 47 can be reproduced by the brightness of the light intensity on the photodetector 50. Further, by detecting the light beam reflected from the optical head device 42 ′ by the photodetector 51 through the mirror 52, the difference in reflectance between the recorded mark of the recording medium 47 and the unrecorded portion of the generated near-field light. By detecting this, the information recorded on the recording medium 47 can be reproduced.
[0036]
【The invention's effect】
As explained above, In the present invention In such an optical head device, a metal film is provided on a plane (an upper surface, a lower surface, or an end surface such as a side surface) formed on an optically flat substrate, and an angle formed by the plane and an optical axis incident on the plane is The angle at which surface plasmons are excited on the metal film, and the periodic fine structure on the metal film, can generate near-field light with high efficiency and stability.
[0037]
Ie Claim 1 The optical head device according to the present invention has a metal film on a plane formed on an optically flat substrate, and an angle formed between the plane and an optical axis incident on the plane is excited by surface plasmon on the metal film. And having a periodic fine structure on the metal film, the periodic structure having the plasmon focusing point as the origin, the wave number of the incident plasmon as k, the incident direction of the plasmon, the origin, and the nth fine structure When the angle formed by αn is αn, the nth microstructure is in an arc shape on the radius R,
kR-kRcosαn = 2πn
Since the phase of the scattered plasmon can be efficiently aligned at the condensing point, the near-field light can be generated with high efficiency and stability.
[0038]
Claim 2 The optical head device according to the present invention has a metal film on a plane formed on an optically flat substrate, and an angle formed between the plane and an optical axis incident on the plane is excited by surface plasmon on the metal film. And has a periodic fine structure on the metal film, and this periodic structure is Plasmonic When the focal point is the origin and the wave number of the incident plasmon is k, the nth fine structure has an arc shape on the radius R,
kR-kRcosαn = 2πn
And,
αn <45 degrees
Since the phase of the scattered plasmon can be efficiently aligned at the focal point, the near-field light can be generated with high efficiency and stability.
[0039]
Claim 3 In the optical head device according to claim 1, Or 2 In addition to the above-described configuration and effects, since the metal film is made of Ag, Au, and Al, surface plasmons can be generated stably and with high efficiency, and as a result, near-field light can be generated with high efficiency and stability.
[0040]
Claim 4 In the optical information recording / reproducing apparatus according to the above, in the optical information recording / reproducing apparatus for recording or reproducing desired information on the recording medium by the near-field light generated from the optical head apparatus held close to the recording medium, the optical head apparatus And claims 1 to 3 By using the optical head device according to any one of the above, the light utilization efficiency is high, a favorable recording mark can be formed, and a signal can be reproduced with a high S / N ratio.
Claims 5 In the optical information recording apparatus according to claim 1, 4 In addition to the above configuration, by using a semiconductor laser as the light source, it is possible to emit linearly polarized light without using a polarizer or the like, so that fine recording marks can be produced at high density, high efficiency and stability at low cost. Can be recorded and played back.
[0041]
Claim 6 In the optical information recording / reproducing apparatus according to claim 1, 4 Or 5 In addition to the above structure, the polarization direction of light incident on the metal film provided in the optical head device is For p-polarized light Therefore, plasmons can be generated with high efficiency, near-field light can be generated with high efficiency and stability, light utilization efficiency is high, good recording marks can be formed, and a high S / N ratio is achieved. The signal can be reproduced.
Claims 7 In the optical information recording / reproducing apparatus according to claim 1, 4 , 5 Or 6 In addition to the above structure, when the substrate of the recording medium is made of plastic or a polymer compound, it can be mass-produced and an optical information recording apparatus can be configured at a lower cost.
[0042]
Claim 8 In the optical information recording / reproducing apparatus according to claim 1, 4 ~ 7 In addition to any of the above structures, a good recording mark can be stably formed by using a recording layer made of AgInSbTe for the recording layer of the recording medium.
Claims 9 In the optical information recording / reproducing apparatus according to claim 1, 4 ~ 8 In addition to any of the above structures, diamond-like carbon is formed on the outermost surface of the recording medium, so that information can be recorded / reproduced with high reliability against surface abrasion.
Further claims 10 In the optical information recording / reproducing apparatus according to claim 1, 4 ~ 8 In addition to any of the above structures, SiN is formed on the outermost surface of the recording medium, so that information can be recorded / reproduced with high reliability against wear on the surface.
[Brief description of the drawings]
FIG. 1 is a perspective view of an optical head device showing an embodiment of the present invention.
2 is a diagram showing an example of the arrangement of microstructures formed on a metal film of the optical head device shown in FIG.
FIG. 3 is a perspective view of an optical head device showing another embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of an optical information recording / reproducing apparatus showing an embodiment of the present invention.
FIG. 5 is a schematic configuration diagram of an optical information recording / reproducing apparatus showing another embodiment of the present invention.
[Explanation of symbols]
11, 31: substrate
12, 32: Metal film
13, 33: Periodic microstructure
41: Laser light source
42, 42 ': Optical head device
43: Holder
44: Protective layer
45: Recording layer
46: Underlayer
47: Recording medium
48: Objective lens
49: Imaging lens
50: Photodetector
51: Photodetector
52: Mirror

Claims (10)

Has a metal film plane formed on an optically flat substrate, the angle between the optical axis incident on the plane and the plane is the angle of the excited surface plasmons in the metal film, the metal Chi lifting a periodic microstructure on the film, and as the origin of the focal point of the periodic structure plasmon, the wave number of the incident plasmon k, the angle of the incident direction and the origin and n-th microstructure of the plasmon αn The nth microstructure is arcuate on radius R,
kR-kR cos αn = 2πn
The optical head device is arranged at a position satisfying the following relationship . The optical head device according to claim 1,
A metal film is provided on a plane formed on an optically flat substrate, and an angle between the plane and an optical axis incident on the plane is an angle at which surface plasmon is excited on the metal film, and the metal If the film has a periodic fine structure, and the periodic structure has the plasmon condensing point as the origin and the wave number of the incident plasmon is k , the nth fine structure has an arc shape on the radius R,
kR-kRcosαn = 2πn
And
An optical head device, wherein the optical head device is disposed at a position satisfying a relationship of αn <45 degrees . The optical head device according to claim 1 or 2 ,
An optical head device , wherein the metal film is made of a metal such as silver (Ag), gold (Au), or aluminum (Al) . In an optical information recording / reproducing apparatus for recording or reproducing desired information on the recording medium by near-field light generated from an optical head device held in proximity to the recording medium ,
An optical information recording / reproducing apparatus using the optical head apparatus according to claim 1 as the optical head apparatus . The optical information recording / reproducing apparatus according to claim 4 .
An optical information recording / reproducing apparatus using a semiconductor laser as a light source . The optical information recording / reproducing apparatus according to claim 4 or 5 ,
An optical information recording / reproducing apparatus , wherein a polarization direction of light incident on a metal film provided in the optical head device is p-polarized with respect to the metal film . The optical information recording / reproducing apparatus according to claim 4, 5 or 6 ,
An optical information recording / reproducing apparatus, wherein the substrate of the recording medium is made of plastic or a polymer compound . The optical information recording / reproducing apparatus according to any one of claims 4 to 7 ,
An optical information recording / reproducing apparatus using a recording layer made of AgInSbTe as a recording layer of the recording medium. The optical information recording / reproducing apparatus according to any one of claims 4 to 8,
An optical information recording / reproducing apparatus , wherein diamond-like carbon is formed on the outermost surface of the recording medium. The optical information recording / reproducing apparatus according to any one of claims 4 to 8 ,
An optical information recording / reproducing apparatus, wherein SiN is formed on the outermost surface of the recording medium.

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