CN100388373C - Super-resolution digital disc with super-lens film structure - Google Patents

Abstract

A super-resolution digital optical disc with a super-lens film structure, comprising a super-lens film (2) and a disc base (3), and a dielectric layer (1), which are dielectric layer (1)/super-lens film (2)/disc base (3) in sequence, wherein the dielectric layer (1) is silicon nitride SiN or ZnS- _SiO2 ; the disc base (3) has pits, the pit size is less than 380nm, and the minimum pit size is 200nm, and the characteristic is that the super-lens film (2) is an Ag(x)Au(1-x) alloy film, wherein the x value varies between 0 and 1. The optical disc structure realizes dynamic reading of information pit size of 200nm or above by using an optical head with a laser wavelength of 650nm red light and a numerical aperture of 0.60. The single-sided single-layer capacity of the optical disc reaches 12-15GB, and the double-sided single-layer capacity reaches 25-30GB.

Description

Super-resolution digital disc with super-lens film structure

technical field

The invention belongs to the field of optical storage in information technology, and is a super-resolution digital disc with a super-lens thin film structure, which is mainly suitable for read-only red light super-resolution digital discs, and can be used for multiple purposes such as audio and video.

Background technique

The rapid development of information technology requires that the optical disc used for information storage must have ultra-high storage density and ultra-fast access rate, which requires that the size of the recording point in the optical disc is getting smaller and smaller. However, as the size of the recording point decreases, the spot size required for reading the recording point also decreases accordingly. It is difficult to read such a small recording point with the existing optical system, because the size of the recording point is smaller than the readout The resolution of the spot, the signal of multiple recording points will appear in the spot, which requires the use of short-wavelength laser and high numerical aperture optical head, but due to the diffraction limit effect of light and the restriction of the numerical aperture of the optical head, the readout Even if the reduction of the spot size is transferred from the current blue light to the purple light, it is only a few times, and the increase of the numerical aperture of the optical head is at the expense of the reduction of the focal depth and the increase of the distortion caused by the eccentricity. Therefore, it is very limited to increase the numerical aperture of the optical head and reduce the laser wavelength to reduce the size of the read spot, so it is very important to study the readout of the record point (super-resolution record point) whose diameter is smaller than the diffraction limit of light. The application value and significance, and it also has great practical application prospects for realizing ultra-high capacity read-only optical discs. For the first time, Yasuda et al. used the film layer structure of "PC substrate/dielectric layer/reflective layer/dielectric layer/mask layer/dielectric layer" to realize the readout of super-resolution recording points in a read-only optical disc (Kouichi Yasuda , Masumi Ono and Katsuhisa Aratani et al.Premastered OpticalDisk by Super-resolution.Jpn.J.Appl.Phys., 1993, 32(11B): 5210-5213), then they changed the optical disk structure to "PC substrate/contrast enhancement layer/dielectric layer/mask layer/dielectric layer/reflective layer/dielectric layer" not only improves the line density of read-only super-resolution optical discs, but also increases the track density (Yutaka K, Kouichi Y, Masumi O et al., Jpn. J. Appl. Phys., 1996, 35 part. 1B 423-428). Yihong Wu et al. theoretically proposed a read-only super-resolution optical disc with a double-mask layer structure of "PC substrate/dielectric layer/upper mask layer/lower mask layer/reflective layer/dielectric layer" to obtain super-resolution recording. Point readout (Yihong Wu, Hock Khoo and Takuyo Kogure et al. Read-only Optical disk with Super-resolution, Appl. Phys. Lett. 1994, 64(24): 3225-3227). Jingsong Wei and Fuxi Gan used a super-resolution reflective film structure to realize the readout of super-resolution information points with a size of 380nm on a device with a laser wavelength of 632.8nm and an optical head with a numerical aperture of 0.40. (Jingsong Wei and Fuxi Gan, "Novel approach to super-resolution pits readout", Opt. Eng. (Lett) 41 (9), 2073-2074 (2002). However, the recording point size read out by the above optical disc structure is only Around the diffraction limit of light, our task is to further read out smaller recording points and obtain a higher signal-to-noise ratio, so that the information recording points on the optical disc are smaller than 380nm.

Contents of the invention

In order to be able to read the information recording points less than 380nm in the read-only optical disc, the present invention proposes a super-resolution digital optical disc with a super-lens film structure, which realizes the recording point size on a dynamic device with a laser wavelength of 650nm and a numerical aperture of 0.60. For readout of 200nm and above, the size of the recording spot is much smaller than the resolution of the dynamic test device.

Technical solution of the present invention is:

A super-resolution digital disc with a super-lens film structure, comprising a super-lens film 2 and a disk base 3, characterized in that: there is also a dielectric layer 1, which in turn is a dielectric layer 1/super-lens film 2/disk base 3, The dielectric layer 1 is silicon nitride SiN or ZnS-SiO ₂ ; the superlens film 2 is Ag, Au or Ag(x)Au(1-x) alloy film, wherein the value of x varies between 0-1; 3 with pits, the pit size is less than 380nm, and the minimum pit size is 200nm. Due to the adoption of the above structure, compared with the prior art, it has excellent performances such as simple structure, low preparation cost and easy process control. The mechanism is that under the action of the readout laser beam, since the superlens film is composed of noble metal and covered with a dielectric layer 1, surface plasmon waves will be excited at the interface of the dielectric layer 1/superlens film 2. , because the surface plasmon wave propagates along the surface, the wave vector is large and the wavelength is short, when it encounters the information recording point, it will be scattered and coupled into propagating light, and the dynamics of smaller super-resolution recording points can be realized by detecting the propagating light read out.

The super-resolution digital disc with the above-mentioned super-lens film structure is characterized in that the Ag, Au or Ag(x)Au(1-x) alloy film material used in the super-lens film 2 has a thickness range of 5-500nm. In the range of 5-500nm, it has excellent performances such as high readout signal-to-noise ratio and stable performance of optical discs.

The above-mentioned super-resolution digital disc with super-lens film structure is characterized in that the dielectric layer 1 is made of silicon nitride SiN or ZnS- _SiO2 with a thickness of 10-500nm, and the thickness range is 10--500nm. In the range of 10--500nm, it has excellent performances such as high readout signal-to-noise ratio and stable disc performance.

The above-mentioned super-resolution digital disc with super-lens film structure is characterized in that the material used for the disc base 3 is polycarbonate or K9 glass, and the thickness of the disc base is 0.6-1.2 mm. Available materials for the disk base 3 are polycarbonate or K9 glass or ordinary quartz glass. Polycarbonate or K9 glass has excellent performances such as good read performance, easy source of material, and compatibility with traditional optical discs.

Technical effect of the present invention:

Compared with the previous technology, the dielectric layer 1 in the super-resolution digital disc with the super-lens thin film structure of the present invention is a protective layer, and is combined with the super-lens thin film layer 2 to reduce the size of the readout spot. Under the dynamic test system with the laser wavelength of 650nm and the numerical aperture of the optical head being 0.60, the readout of the information pit size at or above 200nm can be realized. The read-only CD has a capacity of 12-15GB on one side and a single layer, and a capacity of 25-30GB on both sides and a single layer.

Description of drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention.

Figure 2, the dynamic signal oscilloscope diagram obtained by using SiN as the dielectric layer and Ag as the metalens film.

Figure 3, the dynamic readout signal spectrum obtained by using SiN as the dielectric layer and Au as the metalens film.

Fig. 4, using SiN as the dielectric layer, Ag _0.5 Au _0.5 metalens thin film readout signal spectrum.

Fig. 5 is the spectrum diagram of the readout signal obtained by using ZnS-SiO ₂ as the dielectric layer and Ag as the superlens film.

Figure 6, the spectrum diagram of the readout signal obtained by using ZnS-SiO ₂ as the dielectric layer and Au as the metalens film.

Fig. 7, the frequency spectrum of the signal obtained by using ZnS-SiO ₂ as the dielectric layer and Ag _0.5 Au _0.5 as the metalens film.

Figure 8, the relationship between SiN film thickness and readout signal-to-noise ratio.

Figure 9. Relationship between ZnS- _SiO2 film thickness and readout signal-to-noise ratio.

Figure 10, the relationship between Ag film thickness and readout signal-to-noise ratio.

Figure 11, the relationship between Au film thickness and readout signal-to-noise ratio.

Figure 12, the relationship between Ag _0.5 Au _0.5 film thickness and readout signal-to-noise ratio.

Detailed ways

The embodiment of the present invention is a "read-only red light super-resolution multi-purpose digital disc with a super-lens film structure", as shown in FIG. The dielectric layer 1 is used to protect the superlens thin film layer 2, and combined with the superlens thin film layer 2 is used to reduce the size of the readout spot. The disc substrate 3 is used to prefabricate information dots, and the size of the information dots is 200nm.

Dielectric layer 1 in the embodiment of the present invention is made of silicon nitride or ZnS-SiO ₂ with a thickness of 10-500nm. The value is taken according to the specific situation of implementation, however, when it is lower than 10nm, it will not work, because under this thickness It is difficult to produce high-quality thin films; above 500 nm is also not possible, because at this thickness on the one hand the production costs increase and on the other hand the readout signal decreases. The thickness of the used material of hyperlens film layer 2 is Ag, Au or Ag(x)Au(1-x) alloy thin film of 5-500nm, takes value according to the actual situation of implementation, then not when being lower than 5nm, because in It is difficult to prepare high-quality thin films at this thickness, and at the same time reduce the readout signal-to-noise ratio of the optical disc. It is also not possible when it is higher than 500nm, because there is no surface plasmon wave effect at this thickness, and the dynamic reading of super-resolution information points cannot be realized. out. The dielectric layer 1 , the superlens thin film layer 2 and the disk base 3 jointly form a super-resolution digital optical disc with a superlens thin film structure, as shown in FIG. 1 .

The dielectric layer 1 of the present invention can be made of SiN(x) or ZnS(x)-SiO ₂ (1-x), and the ultralens film 2 can be made of Ag(x), Au(1-x) or Ag(x) Au(1-x) alloy composition (note: parameter x can take any value between 0 and 1). The present invention and its effect are further described below in conjunction with example:

On the polycarbonate substrate with a thickness of 0.6mm, pits with a diameter of 200nm are prefabricated as information points by pressing. The preparation process of the read-only red light super-resolution multi-purpose digital disc with the metalens thin film structure is as follows: using the magnetron sputtering method (sputtering pressure 1.0×10 ^-4 Pa), sequentially plate: noble metal thin film layer 2 and A dielectric layer 1, wherein the dielectric layer 1 is a SiN film with a thickness of 80nm, and the noble metal film layer 2 is an Ag superlens film with a thickness of 40nm. The laser of the device used to detect the signal in the optical disc is a semiconductor laser with a wavelength of 650nm. The numerical aperture of the optical head used is 0.60. According to the diffraction limit formula of light, the diameter of the half-maximum width of the spot is 600nm, far exceeding the pit diameter of 200nm. . Test the read-only red light super-resolution multi-purpose digital disc of the metalens thin film structure in this experiment, then obtained the oscilloscope signal shown in Figure 2, this illustrates "the read-only red light super-resolution multi-purpose optical disc of the super lens thin film structure of the present invention". "Digital optical disk" can realize the readout of information pits with a size of 200nm on a dynamic device with a laser wavelength of 650nm and an optical head with a numerical aperture of 0.60. Spectrum diagram 3 of the dynamic readout signal obtained by using SiN as the dielectric layer and Au as the superlens thin film layer. Spectrum diagram 4 of the dynamic readout signal obtained by using SiN as the dielectric layer and Ag _0.5 Au _0.5 as the superlens thin film layer. Spectrum diagram 5 of the dynamic readout signal obtained by using ZnS-SiO2 as the dielectric layer and Ag as the superlens thin film layer. Spectrum diagram 6 of the dynamic readout signal obtained by using ZnS-SiO2 as the dielectric layer and Au as the superlens thin film layer. Spectrum diagram 7 of the dynamic readout signal obtained by using ZnS-SiO ₂ as the dielectric layer and Ag _0.5 Au _0.5 as the noble metal thin film layer.

Changing the above-mentioned SiN film or ZnS- _SiO2 film thickness can obtain the relationship between the dynamic readout signal and the film thickness shown in Figure 8 and Figure 9, and the relationship is that as the film thickness increases, the signal-to-noise ratio first increases and then decreases. When the thickness of SiN film or ZnS-SiO ₂ film is about 200nm, the signal-to-noise ratio reaches the maximum value.

Change the thickness of Ag thin film or Au thin film or Ag _0.5 Au _0.5 thin film, obtain the relationship between the read signal-to-noise ratio and the film thickness shown in Fig. The noise ratio first increases and then decreases. When the thickness of Ag thin film, Au thin film, Ag _0.5 Au _0.5 thin film is about 300nm, 220nm, 320nm respectively, the signal-to-noise ratio reaches the maximum value.

In summary, adopting the "read-only red light super-resolution multi-purpose digital disc with a hyperlens thin film structure" of the present invention, the information pit size can be realized on a dynamic device where the laser wavelength is 650nm and the numerical aperture of the optical head is 0.60. Readout at 200nm and above.

Claims (4)

1. the super resolution digital optical disc of a super lens membrane structure comprises super lens film (2) and dish base (3), also has dielectric layer (1), and they are followed successively by dielectric layer (1)/super lens film (2)/dish base (3), and dielectric layer (1) is silicon nitride SiN or ZnS-SiO ₂Dish base (3) has the hole point, and the hole spot size is less than 380nm, and the minimum pit spot size is characterized in that at 200nm: super lens film (2) is Ag (x) Au (1-x) alloy firm, and wherein the x value changes between 0-1, does not comprise 0 and 1.

2. the super resolution digital optical disc of super lens membrane structure as claimed in claim 1 is characterized in that the thickness range 5-500nm of Ag (x) Au (1-x) alloy film material that described super lens film (2) is used.

3. the super resolution digital optical disc of super lens membrane structure as claimed in claim 1 or 2 is characterized in that silicon nitride SiN or the ZnS-SiO of dielectric layer (1) by thickness 10-500nm ₂Constitute, thickness range is 10-500nm.

4. the super resolution digital optical disc of super lens membrane structure as claimed in claim 3 is characterized in that described dish base (3) used material is polycarbonate or K9 glass, and the thickness of dish base is 0.6-1.2m.

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