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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 15, Iss. 1 — Jan. 8, 2007
  • pp: 12–23
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Readout contrast beyond diffraction limit by a slab of random nanostructures

Tai Chi Chu, Din Ping Tsai, and Wei-Chih Liu  »View Author Affiliations


Optics Express, Vol. 15, Issue 1, pp. 12-23 (2007)
http://dx.doi.org/10.1364/OE.15.000012


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Abstract

A simplified Fourier optics approach is applied to study how near-field optical disks retrieve evanescent signals through random nanostructure. The statistical properties of the random nanostructures are used to realize the general behavior of near-field optical disks. The mechanism of its super-resolution capability and an analytical expression of the readout contrast of near-field optical disks with random apertures are derived. The resolution of near-field optical disk is determined by the size of the random nanostructure.

© 2007 Optical Society of America

1. Introduction

Nanophtonic devices, such as ultra-high density optical data storage, nano-sized optical telecommunication switches, quantum-confined lasers, nanolithography and nano optical sensor [1–3

1. S. Kawata, M. Ohtsu, and M. Irie, ed., Nano-Optics (Springer, Berlin Heidelberg,2002).

], have made significant progress in recent years. Nevertheless, light in subwavelength optical devices are not easily manipulated because of diffraction limit. If an object is much smaller than the wavelength and the spatial frequency spectrum of the scattered light from the object is broad, the high-spatial-frequency parts that miss the numerical aperture (N.A.) of the lens can not be detected. The limitation of detectable spatial frequencies in the far field determines the diffraction limits of optical system. In order to realize the object of nanophotonics, it is imperative to find practical approaches which overcome diffraction limits.

High spatial frequency fields (evanescent waves) are corresponding to subwavelength fine details of the object, and these components exponentially decay away from the object [4–6

4. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill Inc., Singapore,1996).

]. Those evanescent components are lost in the far field, and subwavelength details are indistinguishable in the far-field region. In 1928, Synge proposed to detect objects by a small hole on a metallic sheet in near-field region [7

7. E. H. Synge, “An application of piezoelectricity to microscopy,” Philos. Mag. 6,356–362 (1928).

]. Using a small aperture close to sample surface can convolute high spatial frequency fields (evanescent waves) from small objects into detectable signals (propagating waves) [8

8. J. M. Vigoureux and D. Courjon, “Detection of nonradiative fields in light of the Heisenberg uncertainty principle and Rayleigh criterion,” Appl. Opt. 31,3170–3177 (1992). [CrossRef] [PubMed]

,9

9. J. M. Vigoureux, F. Depasse, and D. Courjon, “Superrolution of near-field optical microscopy defined from properties of confined electromagnetic waves,” Appl. Opt. 31,3036–3045 (1992). [CrossRef] [PubMed]

]. This concept was first realized by a scanning microwave microscopy with λ/60 resolution in 1972 [10

10. E.A. Ash and G. Nicholls, “ Super-resolution aperture scanning microscope,” Nature 237,510–512 (1972) [CrossRef] [PubMed]

]. With fast progress of fabrication and manipulation techniques, this ideal was accomplished in visible regime by Pohl. et al. in 1984 [11

11. D. W. Pohl, W. Denk, and M. Lanz, “Optical spectroscopy: Image recording with resolution lambda /20,” Appl. Phys. Lett. 44,651–653 (1984). [CrossRef]

]. In conventional near-field optical techniques, near-field optical probes can resolve subwavelength objects far beyond diffraction limits. However, this technology has difficulties of low scanning speed and near-field distance control which are major hurdles on commercial applications.

The idea of using a masking layer to overcome diffraction limit in optical disks appeared as early as in early 1990s [12

12. K. Yasuda, M. Ono, K. Aratani, A. Fukumoto, and M. Kaneko, “Premastered optical disk by superresolution,” Jpn. J. Appl. Phys. 32,5210–5213 (1993) [CrossRef]

,13

13. H. Awano, S. Ohnuki, H. Shirai, and N. Ohta, “Magnetic domain expansion readout for amplification of an ultra high density magneto-optical recording signal,” Appl. Phys. Lett. 69,4257–4259 (1996). [CrossRef]

]. In 1998, a multilayer near-field optical nanostructure was proposed to overcome the diffraction limit by internal disk structures [14

14. J. Tominaga, T. Nakano, and N. Atoda, “An approach for recording and readout beyond the diffraction limit with an Sb thin film,” Appl. Phys. Lett. 73,2078–2080 (1998). [CrossRef]

]. Subsequently, the AgOx-type [15

15. T. Fukaya, D. Büchel, S. Shinbori, J. Tominaga, N. Atoda, D. P. Tsai, and W. C. Lin, “Micro-optical nonlinearity of a silver oxide layer,” J. Appl. Phys. 89,6139–6144 (2001). [CrossRef]

], ZnO-type [16

16. W. C. Lin, T. S. Kao, H. H. Chang, Y. H. Lin, Y. H. Fu, C. T. Wu, K. H. Chen, and D. P. Tsai, “Study of a Super-resolution optical structure: polycarbonate/ZnS-SiO2/ZnO/ZnS-SiO2/Ge2Sb2Te5/ZnS-SiO2,“ Jpn. J. Appl. Phys. 42,1029–1030 (2003). [CrossRef]

] and PtOx-type [17

17. T. Kikukawa, T. Nakano, T. Shima, and J. Tominaga, “Rigid bubble bit formation and huge signal enhancement in super-resolution near-field structure disk with platinum-oxide layer,” Appl. Phys. Lett. 81,4697–4699 (2002). [CrossRef]

] near-field optical disk were developed for higher carrier-to-noise ratio (CNR). A series of studies about the mechanism of AgOx-type near-filed optical disk structure have been reported, and its super-resolution capability is due to the localized surface plasmon enhancements of Ag nanoparticles [18–28

18. D. P. Tsai, J. Kovacs, Z. Wang, M. Moskovits, and V. M. Shalaev, “Photon scanning tunneling microscopy images of optical excitations of fractal metal colloid clusters,” Phys. Rev. Lett. 72,4149–4152 (1994). [CrossRef] [PubMed]

]. The random nanostructures of AgOx layer play an important role in its superior spatial resolution [26

26. T. C. Chu, W.-C. Liu, and D. P. Tsai, “Enhanced resolution induced by random silver nanoparticles in near-field optical disks,” Opt. Commun. 246,561–567 (2005). [CrossRef]

], and work as near-field optical probes which couple evanescent waves into propagating signals. In the pursuit of high-density near-field optical disks, various super-resolution structures have been found to exhibit super-resolution capability, including dielectric, organic, and other complicated structures [29–32

29. F. Zhang, W. Xu, Y. Wang, and F. Gan, “Static optical recording properties of super-resolution near-field structure with Bismuth mask layer,” Jpn. J. Appl. Phys. 43,7802–7806 (2004). [CrossRef]

]. It is necessary to establish a general understanding about the physical mechanism of super-resolution for such a wide variety of near-field optical disks.

In this paper, Fourier optics approach and angular spectrum representation [4–6

4. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill Inc., Singapore,1996).

] are used to analyze the optical effect of a random nanostructure in near-field optical disks. To describe the general property of random nanostructure, its averaged characteristic is considered through the statistical properties. An analytical expression of readout contrast of near-field optical disks with diluted random-distributed apertures is derived. Readout contrasts with random apertures of various densities are simulated numerically.

2. Angular Spectrum Representation of Scattered Fields

If a monochromatic scalar wave propagate in (x,z) plane in a two dimensional model, giving the complex field U(x,0) at z = 0 axis, the Fourier transform of the incident complex field U(x,0),

A(kx)=ʃUx0exp(ikxx)dx,
(1)

is the angular spectrum of U(x,0). The angular spectrum can be regarded as a decomposition of plane waves with wave vector k. The field U(x,z) can be written in terms of the angular spectrum of incident field

Uxz=ʃA(kx)exp(i(kxx+kzz))dkx,
(2)

where kz=k2kx2,k=2πλ, and λ is the wavelength of incident light. The intensity of the component with wave vector kx is

I(kx)=A(kx)2.
(3)

In commercial CD or DVD, the data is recorded by serial recording marks, and the realistic recording mark chains are very complicated. To simplify calculation, the periodic recording mark chain in the optical disk is represented by a grating. The near-field active layer consists of random nanostructures and its optical property can be characterized by a random optical function. Angular spectrum representation is used to calculate far fields of the near-field optical disks, and the model is shown in Fig. 1. The beam width of incident Gaussian wave is a. The far-field intensity of the near-field optical disk is

I(kx)=14aπ72[ʃex'2a2G(x')F(x')eikxx'dx']*[ʃex2a2G(x)F(x)eikxxdx],
(4)

where G(x) is the optical function of the grating and F(x) is the optical function of the random nanostructure in the near-field optical disk. The refractive index of recording mark is different from the surrounding, and the optical reflectance changes when reading laser beam scan from surrounding to a recording mark. In experimental measurements, the reflection contrasts between recording marks and surrounding are represented by Carrier-to-Noise-Ratio (CNR). In order to compare with the experimental CNR of optical disks, far-field intensity differences between on-mark and off-mark situations are calculated to correspond to readout contrasts. The on-mark situation means that the incident light focuses on the recording mark, and off-mark situation means that the incident light focuses between adjacent marks. The grating optical function of on-mark case is

G(x)=12(1+cos(gx)),
(5)

where g =π / L and L is the recording mark size. For the off-mark case, the grating shift a half period.

G(x)=12(1cos(gx)).
(6)

So the far-field intensity difference between on-mark and off-mark situations, which represents readout contrast of an optical disk, is

ΔI(kx)=14aπ72ʃʃdxdx'ex2x'2a2(cos(gx)+cos(gx'))F(x)F(x')eikx(xx').
(7)
Fig. 1. Model of the near-field optical disk with a random nanostructure.

It is noted that the far-field intensity differences of a near-field optical disk with a particular random nanostructure only relates to that specific random nanostructures. To avoid this problem, statistical approach is used to realize general properties of the near-field optical disk with random nanostructures. For the averaged random structure, <F(x)F(x’)> is decided by the statistical properties, autocorrelation function, of random structure. The autocorrelation function can be described as < F(x)F(x') > = σ 2 C(xx') + h 2, where C(xx’) is correlation function of two random functions F(x) and F(x’), σ is root-mean-square of random structure F(x), and h is mean value of F(x). The correlation function usually is assumed to be Gaussian C(xx') = exp(−(xx')2 / l 2), where l is the correlation length. The averaged intensity difference is

ΔI(kx)=14aπ72ʃʃdxdx'ex2x'2a2(cos(gx)+cos(gx'))F(x)F(x')eikx(xx').
=14aπ72eg2a28{h2[exp(a2(kxg2)22)+exp(a2(kx+g2)22)]
+σ2l2a2+l2[exp(a2l2(kxg2)22(2a2+l2))+exp(a2l2(kx+g2)22(2a2+l2))]}.
(8)

The first term of average intensity difference is from mean value h 2 of random structure and is the same as the case of uniform thin film with transmittance h 2. The second term is from the correlation function of random structure. However, the exp(−g2a2/8) term dominates while mark size approaches to 0 (g→∞), and the average intensity differences are close to cases of uniform thin film with subwavelength record marks. But in Eq. (8) the average intensity difference is still subject to diffraction limit and disappears for subwavelength recording marks. The reason is that far-field intensity of on-mark case may be higher or lower than that of off-mark cases because of random structure, and the intensity difference (Ion-mark−Ioff-mark) of recording marks much smaller than diffraction limit could be positive or negative for different random structures. We believe the contrast inversion in the intensity difference signal of is real and can be detected experimentally for small recording marks, although experimental CNR measurements of near-field optical disks concerned only the variations of readout signals along recording mark train. The enhancements of difference signal are lost in the average process, so the reasonable contrasts between on-mark and off-marks cases are absolute values of intensity differences.

It is difficult to average absolute values of intensity differences, so the root mean square (RMS) of far-field intensity differences would provide more reasonable average difference signals. From Eq. (7), the square of intensity difference is

ΔI2(kx)=(14aπ72)2ʃʃʃʃdx1dx1'dx2dx2'ex12x1'2x22x2'2a2(cos(gx1)+cos(gx1'))·(cos(gx2)+cos(gx2'))eikx(x1x1'+x2x2')F(x1)F(x1')F(x2)F(x2').
(9)

The optical function of random nanostructures is the combination of fluctuations at random positions

F(x1)F(x1')F(x2)F(x2')=i,j,l,mFx1xiF(x1',xj)Fx2xlF(x2',xm),
(10)

where the xi, xj, xl, xm are independent random variables which are the center positions of fluctuations. Those random variables are assumed to be uniformly distributed. From Eq. (9) and (10), the square of far-field intensity difference is a function of xi, xj, xl, xm

ΔI2(kx)=i,j,l,mΔI2kxxixjxlxm.
(11)

The expectation value of square of intensity difference is

ΔI2(kx)=i,j,l,mʃʃʃʃdxidxjdxldxmΔI2kxxixjxlxmP(xi)P(xj)P(xl)P(xm)
=CʃdxiΔI2kxxi=xj=xl=xmP(xi)+O(C2),
(12)

where the P(xi), P(xj), P(xl), P(xm) are probability density functions of those random variables and C is the (linear) density of random fluctuations. For a dilute case, the density is small and the first term of Eq. (12) dominates the behavior. It is straightforward to calculate the RMS of intensity differences from the first term of Eq. (12) for dilute cases. The RMS of the difference signals for both dilute and dense cases ae simulated by numerical method. The numerical RMS is calculated from Eq. (9) directly, and 12800 realizations of random nanostructures with the same statistical nature are averaged to obtain the far-field difference signals. Standard deviations of numerical results are under 1% of the readout contrast signals. To make the physical meaning clear, we use readout contrast signals instead of RMS of the far-field difference signals in the following sections.

3. Super-resolution of random nanostructures

F(xi)=i=1Ne(xxi)2D2,
(13)

where xi are uniformly-distributed random positions and N is the amount of apertures. From the first term of Eq. (12) and (13), the readout contrast (RMS of far-field intensity difference) for dilute cases is

ΔI2(kx)=aD4π3(a2+D2)(ea2D2(kx+g2)22(a2+D2)+ea2D2(kxg2)22(a2+D2))
·[(a2+D2)232D[eg2a24+eg2a2D24(a2+D2)]]12.
(14)

The readout contrast of random nanostructure is normalized to a transparent uniform thin film.

Fig. 2 Illustration of readout contrast in spatial frequency domain: (a) Aperture size D is close Gaussian beam width a. (b) Aperture size D is much smaller than the beam width a.

Using the conventional DVD scheme, the wavelength λ is 650 nm and the Gaussian beam width a is 542 nm. Figure 3(a) shows readout contrast with different aperture size for a normal transmitting light, i.e., kx = 0. The readout contrast signals of a uniform thin film are used as reference, and the signals drop around 0.9λ mark size due to diffraction limit. For the cases of D = λ, the size of random apertures is close to the wavelength, so the behavior of readout contrast signal is similar to the reference case. While the size of random apertures is smaller than the wavelength, the signals of small recording marks decrease very slowly. The signals of D = 0.1λ case apparently drop around 0.1λ mark size, because the aperture size decides the resolution limit of random nanostructures. For the cases of D = 0.01λ, the signals are almost flat for mark size larger than 0.02λ, but become weaker than the signals of the D = 0.1λ cases. Fig. 3(b) shows the results for N.A. = 0.6 cases, and these result are similar to the cases of normal transmitting limit. The numerical results of dilute apertures are also calculated to compare with the analytic results. The ratio between aperture area and total calculating regime is 5%. The numerical results are normalized to the analytic readout contrast signals at 0.8λ mark size. The behavior of numerical results agrees very well with the analytic results and it confirms the dilute approximation of Eq. (12).

Fig. 3 Readout contrast signals of analytical results (solid line) and numerical results (mark) with various aperture size for (a) for normal transmitting (kx = 0) cases and (b) N.A. = 0.6 cases.

Both analytical and numerical results demonstrate that readout contrast signals of recording marks smaller than diffraction limit decrease slowly for small random apertures. The readout contrast signals of small random apertures drop only when recording mark size approaches to aperture size. This behavior reveals the general properties of random aperture, i.e., broad spatial frequency of small random apertures convolute out evanescent signals and the size of random apertures determine the resolution capability. Readout contrast signals of large recording mark size smear because of random nanostructure, but the readout contrast signals of small recording mark size are highly enhanced. On the other hand, an equivalent process is to readout the random nanostructures using the diffraction grating with a specific spatial frequency and the matched evanescent wave from the random nanostructures is convoluted into propagating wave.

Fig. 4 Numerical readout contrast signals of dilute case for (a) kx = 0, and (b) N.A. = 0.6 cases. The coverage rate is 65%.

The numerical results of dense cases are simulated to compare with dilute cases. The ratio between aperture area and total calculating regime is 65% in Fig. 4. The readout contrast signals are normalized at 6λ mark size. The readout contrast signals of D = 0.1λ cases drop around 0.1λ mark size which are similar to the dilute situations in Fig. 3. For the cases of D = 0.01λ, the readout contrast signals are almost flat for mark size are larger than 0.01λ. Both the cases of kx = 0 and N.A. = 0.6 exhibit similar behaviors which also appear in the results of dilute situation, though the readout contrast signals in Fig. 4 are about 5 db weaker than those of dilute situation. Those cases with even higher coverage ratio are also simulated and there is no characteristic difference between dilute cases and dense cases, even when the coverage ratio is as high as 99%. This surprising phenomenon can be explained by Babinet’s principle. The distribution of light diffracted by a screen with apertures is the same as the case with complementary screen. So signals of dense cases are similar to those of dilute cases.

4. Waveform of near-field optical disks with random nanostructures

G(x)=12(1+cos(g(x+l))).
(15)

Using Eq. (3), (13) and (15), the transmitting intensity is

Ilxi=14π52(aD2a2+D2)const·+cos(g(a2xia2+D2+l))·e2xi2a2D2(kx+g)24a2D2kx24(a2+D2)+cos(g(a2xia2+D2+l))·e2xi2a2D2(kxg)24a2D2kx24(a2+D2)+cos(2g(a2xia2+D2+l))·e2xi2a2D2(kx+g)24a2D2(kxg)24(a2+D2)
(16)

I2(l)~e11a2D2g216(a2+D2)(ea2D2(kx+g4)2(a2+D2)+ea2D2(kxg4)2(a2+D2))
·(cos(3g·l)e9a4g216(a2+D2)+cos(g·l)ea4g216(a2+D2))+O(ea2g24).
(17)
Fig. 5 (a) Waveform of single frequency case for kx = 0 and D = 0.1λ ; (b) Numerical waveform of two-frequency case for kx = 0 and D = 0.1λ .

In Eq. (17), the exp(−a2g2/4) term decrease dramatically for small recording mark (g→∞), and the exp(−9a4g2/16(a2+D2)) term is much smaller than exp(−a4g2/16(a2+D2)) term which is the dominating term. The analytical RMS of I(l) (waveform) for different mark size (L) is shown in Fig. 5 (a), and the aperture size D is 0.1λ. The RMS of transmitting intensity displays a clear readout waveform while mark size L is 0.5λ(above diffraction limit). The readout waveform are well readable even for mark size smaller than diffraction limit (L = 0.4 λ and 0.35λ ). While mark size L is 0.3λ, which is close to the aperture size (0.1λ), the readout waveform becomes weaker but still distinguishable. The analytical result in Eq. (17) implies that readout contrast signals of near-field optical disks diminish much slower than those of conventional optical disks.

Above results present the readout waveform of a single-frequency pattern, however, realistic recording mark chain in optical disk consists of random patterns of recording marks. Here a two-frequency pattern is calculated to serve as an example. The optical function of two-frequency grating is assigned to be G(x) = 1 + cos(gx+θ ) + cos(1.7gx+θ ), and the phase θ indicates the shift of Gaussian beam, which is corresponding to l in Eq. (15). The simulated RMS of intensity I(θ ) is shown in Fig. 5 (b), and the coverage ratio of random apertures is 5%. Results show that transmitting variations are distinguishable for both cases of 0.77λ and 0.3λ mark size. The intensity minimums of I(θ ) are around 1.25π which is different from the single frequency case( minimum is at π ), and waveforms show asymmetric behaviors. The waveform differences between single frequency and two-frequency cases indicate that multi-frequency signals are possible to be coupled out by random apertures.

5. Near-field optical disks with random nanostructures

The concept of RMS signals in Eq. (12) can be easily applied to a more realistic model of near-field optical disks. The structure of a near-field optical disk is shown in Fig. 5. There is a 15 nm dielectric spacing layer between the random nanostructure and periodic recording layer. Incident Gaussian beam with beam width a illuminates from above through the random nanostructure, then it passes the spacing layer to the periodic recording layer. The optical waves are reflected from the periodic recording layer, and finally, the reflected wave passes through the spacing layer and the random nanostructure again. The far-field signals are obtained from angular spectrum representation of the reflected waves.

Fig. 5 A realistic model of near-field optical disk with random nanostructures.

The optical function of random nanostructures is random Gaussian apertures as in Eq. (13). The wavelength λ is 650 nm and the beam width a is 542 nm. 15000 realizations of random nanostructures with the same statistical properties are used to obtain the readout contrast between on-mark and off-mark situations. The coverage ratio of apertures is 65%. The average RMS signals for N.A. = 0.6 cases are shown in Fig. 6 and all signals are normalized to the far-field signals of 6λ mark size. In the cases without random nanostructures, the far-field signals drop around 0.6λ mark size because of diffraction limit. Signals of smaller recording marks are enhanced for D = 0.1λ and D = 0.01λ cases. For example, in the case of D = 0.1λ, the readout contrast signals decrease slowly for recording marks larger than 0.1λ and drop around 0.1λ mark size. The behaviors of readout contrast signals are similar to results of Fig. 4, only the readout contrast signals decrease more for smaller recording marks. It is because the wave travels extra distance. Those results indicate that contrast between on-mark and off-mark situations is determined by the size of random nanostructures.

Fig. 6 Readout contrasts of numerical results for N.A. = 0.6 for a model of near-field optical disk.

6. Conclusion

Though the complex phenomena of realistic optical disks are not fully included in this model, this theory describes a clear picture about how the random nanostructures in high-density near-field optical disks enhance the optical resolution. It provides an approach to explore optics in subwavelength regime with random nanostructures and lays a foundation for high-density near-field optical storage.

Acknowledgments

This work is supported by National Science Council (NSC95-2112-M-002-036-MY2 and NSC95-2112-M-003-024-MY2) and Ministry of Economical Affair (95-EC-17-A-08-S1-0006) of Taiwan, Republic of China.

References and links

1.

S. Kawata, M. Ohtsu, and M. Irie, ed., Nano-Optics (Springer, Berlin Heidelberg,2002).

2.

M. Ohtsu, ed., Near-Field Nano/Atom Optics and Technology (Springer, Tokyo,1998). [CrossRef]

3.

P. N. Prasad, Nanophotonics (John Wiley & Sons, Inc., Hoboken, New Jersey,2004). [CrossRef]

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E. Wolf and M. Nieto-Vesperinas, “Analyticity of the angular spectrum amplitude of scattered fields and some of its consequences,” J. Opt. Soc. Am. A 2,886–890 (1985). [CrossRef]

7.

E. H. Synge, “An application of piezoelectricity to microscopy,” Philos. Mag. 6,356–362 (1928).

8.

J. M. Vigoureux and D. Courjon, “Detection of nonradiative fields in light of the Heisenberg uncertainty principle and Rayleigh criterion,” Appl. Opt. 31,3170–3177 (1992). [CrossRef] [PubMed]

9.

J. M. Vigoureux, F. Depasse, and D. Courjon, “Superrolution of near-field optical microscopy defined from properties of confined electromagnetic waves,” Appl. Opt. 31,3036–3045 (1992). [CrossRef] [PubMed]

10.

E.A. Ash and G. Nicholls, “ Super-resolution aperture scanning microscope,” Nature 237,510–512 (1972) [CrossRef] [PubMed]

11.

D. W. Pohl, W. Denk, and M. Lanz, “Optical spectroscopy: Image recording with resolution lambda /20,” Appl. Phys. Lett. 44,651–653 (1984). [CrossRef]

12.

K. Yasuda, M. Ono, K. Aratani, A. Fukumoto, and M. Kaneko, “Premastered optical disk by superresolution,” Jpn. J. Appl. Phys. 32,5210–5213 (1993) [CrossRef]

13.

H. Awano, S. Ohnuki, H. Shirai, and N. Ohta, “Magnetic domain expansion readout for amplification of an ultra high density magneto-optical recording signal,” Appl. Phys. Lett. 69,4257–4259 (1996). [CrossRef]

14.

J. Tominaga, T. Nakano, and N. Atoda, “An approach for recording and readout beyond the diffraction limit with an Sb thin film,” Appl. Phys. Lett. 73,2078–2080 (1998). [CrossRef]

15.

T. Fukaya, D. Büchel, S. Shinbori, J. Tominaga, N. Atoda, D. P. Tsai, and W. C. Lin, “Micro-optical nonlinearity of a silver oxide layer,” J. Appl. Phys. 89,6139–6144 (2001). [CrossRef]

16.

W. C. Lin, T. S. Kao, H. H. Chang, Y. H. Lin, Y. H. Fu, C. T. Wu, K. H. Chen, and D. P. Tsai, “Study of a Super-resolution optical structure: polycarbonate/ZnS-SiO2/ZnO/ZnS-SiO2/Ge2Sb2Te5/ZnS-SiO2,“ Jpn. J. Appl. Phys. 42,1029–1030 (2003). [CrossRef]

17.

T. Kikukawa, T. Nakano, T. Shima, and J. Tominaga, “Rigid bubble bit formation and huge signal enhancement in super-resolution near-field structure disk with platinum-oxide layer,” Appl. Phys. Lett. 81,4697–4699 (2002). [CrossRef]

18.

D. P. Tsai, J. Kovacs, Z. Wang, M. Moskovits, and V. M. Shalaev, “Photon scanning tunneling microscopy images of optical excitations of fractal metal colloid clusters,” Phys. Rev. Lett. 72,4149–4152 (1994). [CrossRef] [PubMed]

19.

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20.

F. H. Ho, W. Y. Lin, H. H. Chang, Y. H. Lin, W.-C. Liu, and D. P. Tsai, “Nonlinear optical absorption in the AgOx-type super-resolution near-field structure,” Jap. J. Appl. Phys. 40,4101–4102 (2001). [CrossRef]

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F. H. Ho, H. H. Chang, Y. H. Lin, B.-M. Chen, S.-Y. Wang, and D. P. Tsai, “Functional structures of AgOx thin film for near-field recording,” Jpn. J. Appl. Phys., Part 1 42,1000–1004 (2003). [CrossRef]

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W.-C. Liu and D. P. Tsai, “Nonlinear near-field optical effects of the AgOx-Type super-resolution near-field structure,” Jpn. J. Appl. Phys. 42, Part 1,1031–1032 (2003). [CrossRef]

24.

W.-C. Liu, M.-Y. Ng, and D. P. Tsai, “Surface plasmon effects on the far-field signals of AgOx-type super-resolution near-field structure,” Jpn. J. Appl. Phys. 43,4713–4717 (2004). [CrossRef]

25.

T. C. Chu, W.-C. Liu, and D. P. Tsai, “Near- and far-field optical properties of embedded scatters in AgOx-type super-resolution near-field structures,” Scanning, 26,102–105 (2004).

26.

T. C. Chu, W.-C. Liu, and D. P. Tsai, “Enhanced resolution induced by random silver nanoparticles in near-field optical disks,” Opt. Commun. 246,561–567 (2005). [CrossRef]

27.

J. M. Ji, L. P. Shi, K. G. Lim, X. S. Miao, H. X. Yang, and T. C. Chong, “Enhanced scattering of random-distribution nanoparticles and evanescent field in super-resolution near-field structure,” Jpn. J. Appl. Phys. 44,3620–3622 (2005). [CrossRef]

28.

M.-Y. Ng and W.-C. Liu, “Super-resolution and frequency-dependent efficiency of near-field optical disks with silver nanoparticles,” Opt. Exp. 13,9422–9430 (2005). [CrossRef]

29.

F. Zhang, W. Xu, Y. Wang, and F. Gan, “Static optical recording properties of super-resolution near-field structure with Bismuth mask layer,” Jpn. J. Appl. Phys. 43,7802–7806 (2004). [CrossRef]

30.

Y. H. Fu, F. H. Ho, W.-C. Hsu, S.-Y. Tsai, and D. P. Tsai, “Nonlinear optical properties of the Au-SiO nanocomposite superresolution near-field thin film,” Jpn. J. Appl. Phys. 43,5020–5023 (2004). [CrossRef]

31.

H.-H. Chiang, W.-C. Hsu, S.-Y. Tsai, M.-R. Tseng, S.-P. Hsu, T.-T. Hung, C.-J. Chang, and P. C. Kuo, “Thermal and optical properties of organic dyes for duper-resolution recordable disks,” Jpn. J. Appl. Phys. 42,997–999 (2003). [CrossRef]

32.

T. Shima, M. Kuwahara, T. Fukaya, T. Nakano, and J. Tominaga, “Super-resolutional readout disk with metal-free phthalocyanine recording layer,” Jpn. J. Appl. Phys. 43,L88–L90 (2004). [CrossRef]

33.

T. Kikukawa, T. Kato, H. Shingai, and H. Utsunomiya, “High-density read-only memory disc with super resolution reflective layer,” Jpn. J. Appl. Phys. 40,1624–1628 (2001). [CrossRef]

34.

J. W. Fang, C. C. Wu, A. Liao, W. C. Lin, and D. P. Tsai, “Implementation of practical super-resolution near-field structure system using commercial drive,” Jap. J. Appl. Phys. 45,1383–1384 (2006).. [CrossRef]

OCIS Codes
(050.1220) Diffraction and gratings : Apertures
(050.2770) Diffraction and gratings : Gratings
(070.2580) Fourier optics and signal processing : Paraxial wave optics
(210.4590) Optical data storage : Optical disks

ToC Category:
Diffraction and Gratings

History
Original Manuscript: September 7, 2006
Revised Manuscript: November 16, 2006
Manuscript Accepted: December 27, 2006
Published: January 8, 2007

Citation
Tai Chi Chu, Din Ping Tsai, and Wei-Chih Liu, "Readout contrast beyond diffraction limit by a slab of random nanostructures," Opt. Express 15, 12-23 (2007)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-1-12


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References

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  24. W.-C. Liu, M.-Y. Ng and D. P. Tsai, "Surface plasmon effects on the far-field signals of AgOx-type super-resolution near-field structure," Jpn. J. Appl. Phys. 43, 4713-4717 (2004). [CrossRef]
  25. T. C. Chu, W.-C. Liu, and D. P. Tsai, "Near- and far-field optical properties of embedded scatters in AgOx-type super-resolution near-field structures," Scanning,  26, 102-105 (2004).
  26. T. C. Chu, W.-C. Liu, and D. P. Tsai, "Enhanced resolution induced by random silver nanoparticles in near-field optical disks," Opt. Commun. 246, 561-567 (2005). [CrossRef]
  27. J. M. Ji, L. P. Shi, K. G. Lim, X. S. Miao, H. X. Yang and T. C. Chong, "Enhanced scattering of random-distribution nanoparticles and evanescent field in super-resolution near-field structure," Jpn. J. Appl. Phys. 44, 3620-3622 (2005). [CrossRef]
  28. M.-Y. Ng and W.-C. Liu, "Super-resolution and frequency-dependent efficiency of near-field optical disks with silver nanoparticles," Opt. Exp. 13, 9422-9430 (2005). [CrossRef]
  29. F. Zhang, W. Xu, Y. Wang and F. Gan, "Static optical recording properties of super-resolution near-field structure with Bismuth mask layer," Jpn. J. Appl. Phys. 43, 7802-7806 (2004). [CrossRef]
  30. Y. H. Fu, F. H. Ho, W.-C. Hsu, S.-Y. Tsai and D. P. Tsai, "Nonlinear optical properties of the Au-SiO nanocomposite superresolution near-field thin film," Jpn. J. Appl. Phys. 43, 5020-5023 (2004). [CrossRef]
  31. H.-H. Chiang, W.-C. Hsu, S.-Y. Tsai, M.-R. Tseng, S.-P. Hsu, T.-T. Hung, C.-J. Chang and P. C. Kuo, "Thermal and optical properties of organic dyes for duper-resolution recordable disks," Jpn. J. Appl. Phys. 42, 997-999 (2003). [CrossRef]
  32. T. Shima, M. Kuwahara, T. Fukaya, T. Nakano and J. Tominaga, "Super-resolutional readout disk with metal-free phthalocyanine recording layer," Jpn. J. Appl. Phys. 43, L88-L90 (2004). [CrossRef]
  33. T. Kikukawa, T. Kato, H. Shingai and H. Utsunomiya, "High-density read-only memory disc with super resolution reflective layer," Jpn. J. Appl. Phys. 40, 1624-1628 (2001). [CrossRef]
  34. J. W. Fang, C. C. Wu, A. Liao. W. C. Lin and D. P. Tsai, "Implementation of practical super-resolution near-field structure system using commercial drive," Jap. J. Appl. Phys. 45, 1383-1384 (2006). [CrossRef]

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