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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 8 — Apr. 9, 2012
  • pp: 9064–9078
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Numerical retrieval of thin aluminium layer properties from SPR experimental data

Dominique Barchiesi  »View Author Affiliations


Optics Express, Vol. 20, Issue 8, pp. 9064-9078 (2012)
http://dx.doi.org/10.1364/OE.20.009064


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Abstract

The inverse problem for Surface Plasmon Resonance measurements [1] on a thin layer of aluminium in the Kretschmann configuration, is solved with a Particle Swarm Optimization method. The optical indexes as well as the geometrical parameters are found for the best fit of the experimental reflection coefficient in s and p polarization, for four samples, under three theoretical hypothesis on materials: the metal layer is pure, melted with its oxyde, or coated with oxyde. The influence of the thickness of the metal layer on its optical properties is then investigated.

© 2012 OSA

1. Introduction

In 1959, the optical absorption in the Kretschmann configuration [2

2. E. Kretschmann, “Die bestimmung optischer konstanten von metallen durch anregung von oberflachenplasmaschwingungen,” Z. Phys. 241, 313–324 (1971). [CrossRef]

] due to the excitation of the surface plasma wave between the metal and air has first been seen and discussed by Turbadar [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

], however, without relating this effect to surface plasma waves [3

3. A. Otto and W. Sohler, “Modification of the total reflection modes in a dielectric film by one metal boundary,” Opt. Commun. 3, 254–258 (1971). [CrossRef]

]. Turbadar [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

] published measurements of the reflectance by four aluminium layers deposited on a glass prism, in this setup. The aluminium films were deposited on glass by evaporation from tungsten loops after pre-fusing in vacuum. The pressure during evaporation was about 10−5 mm Hg. The evaporation time was not strictly controlled but was usually less than 30 seconds. The substrate, polish optical glass, was chemically cleaned and then cleaned by ionic bombardment immediately before evaporation. The substrate was made of a right angle prism, with the Al film deposited on its hypotenuse [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

]. The experimental results were compared to theoretical curves, but some discrepancies were found and never explained, especially for small thicknesses of aluminium. The sample was supposed to be a pure Aluminium layer above a glass prism, with bulk optical index.

We propose an explanation of these differences, by comparing the best fits of the experimental data, under the hypothesis of the possible oxydation of aluminium before optical measurements. The possible dependence of the optical index of aluminium with the thickness of the layer is also discussed. This inverse problem method is similar to that proposed in Ref. [4

4. D. Macias and D. Barchiesi, “Identification of unknown experimental parameters from noisy apertureless scanning near-field optical microscope data with an evolutionary procedure,” Opt. Lett. 30, 2557–2559 (2005). [CrossRef] [PubMed]

], but uses the Particle Swarm Method (PSO) [5

5. J. Kennedy and R. Eberhart, “Particle swarm optimization,” in Proceedings of IEEE International Conference on Neural Networks (IV) (IEEE, 1995), pp. 1942–1948.

] instead of the evolutionary method. For plasmonic applications, a recent benchmark has proved that the PSO could be more efficient than an evolutionary method, based on selection procedure [6

6. S. Kessentini, D. Barchiesi, T. Grosges, L. Giraud-Moreau, and M. Lamy de la Chapelle, “Adaptive non-uniform particle swarm application to plasmonic design,” Int. J. Appl. Metaheuristic Comput. 2, 18–28 (2011). [CrossRef]

, 7

7. S. Kessentini, D. Barchiesi, T. Grosges, and M. Lamy de la Chapelle, “Particle swarm optimization and evolutionary methods for plasmonic biomedical applications,” in Proceedings of IEEE Congress on Evolutionary Computation (CEC) (IEEE, 2010), pp. 2315–2320.

]. The PSO is used to retrieve the experimental parameters that were unknown in the original paper by Turbadar [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

]. The PSO and the models are described in the section 2, the results of the inverse problem procedure are proposed in the section 3 before a physical discussion in Sec. 4 and concluding remarks.

2. The inverse problem procedure

2.1. The Particle Swarm Optimization method

2.2. The models

Two multilayer models are proposed to describe the experiments. Both are based on the computation of the reflectance of the metal layer in the Kretschmann configuration [12

12. E. Kretschmann, “The ATR method with focused light - application to guided waves on a grating,” Opt. Commun. 23, 41–44 (1978). [CrossRef]

]. All experimental data were obtained with an illumination wavelength λ0 = 550 nm and the medium above the metal layer was air (relative permittivity εAir=1) [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

]. Figure 1 illustrates the experimental setup, where the aluminium layer is deposited on a glass prism.

Fig. 1 Experimental setup used in Ref. [1].

In the first model, only one metal layer is considered. In the second, one a two layers system is introduced, to be able to introduce aluminium oxyde above the surface of the metal.

2.2.1. Single layer

Figure 1(a) shows the multilayer model of the experiments. The fitness function F (Eq. 1) evaluation requires the computation of the reflectance in both polarizations (s) and (p). These generalized Fresnel coefficients are easy to calculate, assuming monochromatic incoming plane wave [13

13. D. Barchiesi, “Optimization of biosensors,” in New Perspectives in biosensors technology and applications, P. A. Serra, ed. (INTECH Open Access, Rijeka, Croatia, 2011), pp. 105–126.

]:
Rt=|r12+r23exp(2ιew2)1+r12r23exp(2ιew2)|2|1(r01)2|2.
(4)
wi=2π(εiεV sin2(ϕg))1/2/λ0 are the normal to the interface component of the wave vector (see Fig. 1). The coefficients rii+1 depends on the polarization and on the permittivites of two successive media (Fig. 1):
rii+1=wiwi+1wi+wi+1 in(s)polarization,
(5)
rii+1=εi+1wiεiwi+1εi+1wi+εiwi+1 in(p)polarization.
(6)
The model of homogenous gold layer and the performances of the optimization method are fully discussed in Ref. [13

13. D. Barchiesi, “Optimization of biosensors,” in New Perspectives in biosensors technology and applications, P. A. Serra, ed. (INTECH Open Access, Rijeka, Croatia, 2011), pp. 105–126.

].

The following material hypothesis are successively investigated:
  • H1a The layer is made of pure aluminium with bulk complex relative permittivity ε2 = εAl. The vector of unknown parameters is x(t) = (e, εV). This model was used in the reference paper [1

    1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

    ].
  • H1b The layer is made of pure aluminium with unknown complex relative permittivity εAl. The vector of unknown parameters is x(t) = (e, εV, εAl).
  • H1c The layer is made of an homogeneous composite medium (HCM) of aluminium and aluminium oxyde Al2O3, with bulk relative permittivities εAl and εAl2O3. In the Bruggeman formalism, oxyde and metal are both supposed to be dispersed in the HCM [14

    14. D. A. G. Bruggeman, “Berechnung verschiedener physikalischer konstanten von heterogenen substantzen. i. dielektrizitätskonstanten und leifähigkeiten der misckörper aus isotropen substanzen,” Ann. Phys. (Leipzig) 24, 636–679 (1935).

    ]. This formulation is also known in optics as the Geometrical Effective Medium Approximation (GEMA) which was developed for absorbing multilayer structures [15

    15. A. J. Abu El-Haija, “Effective medium approximation for the effective optical constants of a bilayer and a multilayer structure based on the characteristic matrix technique,” J. Appl. Phys. 93, 2590–2594 (2003). [CrossRef]

    ] The vector of unknown parameters is x(t) = (e,εV, fo), where fo is the fraction of aluminium oxyde, therefore fo ∈ [0; 1]. :
    ε2=foεAl2O3+(1fo)εAl,
    (7)
  • H1d The layer is made of a mixing of pure aluminium and aluminium oxyde Al2O3, with respectively bulk relative permittivities εAl2O3 and εAl. The Maxwell-Garnet model [16

    16. W. R. Tinga, W. A. G. Voss, and D. F. Blossey, “Generalized approach to multiphase dielectric mixture theory,” J. Appl. Phys. 44, 3897–3903 (1973). [CrossRef]

    ] of inclusion is used:
    ε2=εAl(1+2fo)εAl2O3+2(1fo)εAl(1fo)εAl2O3+(fo+2)εAl.
    (8)

    The aluminium oxyde is considered as inclusions in the metal. The vector of unknown parameters is x(t) = (e,εV, fo).

The Bruggeman and Maxwell-Garnett models are not equivalent excepted if fo = 0 or fo = 1. The real part of the Bruggeman relative permittivity is lower than the real part of the Maxwell-Garnett relative permittivity, on the contrary of its imaginary part.

2.2.2. Two layers

Figure 1(b) shows the multilayer model of the experiments. The theoretical reflectance can be written
Rt=|r(r01)2|2.|r12+r23e2ιe2w2+r34e2ι(e2w2+e3w3)+r12r23r34e2ιe3w31+r12r23exp(2ιe2w2)+r12r34e2ι(e2w2+e3w3)+r23r34e2ιe3w3|2.
(9)
This model has been used for the optimization of Surface Plasmon Resonance biosensor [18

18. D. Barchiesi, D. Macías, L. Belmar-Letellier, D. Van Labeke, M. Lamy de la Chapelle, T. Toury, E. Kremer, L. Moreau, and T. Grosges, “Plasmonics: Influence of the intermediate (or stick) layer on the efficiency of sensors,” Appl. Phys. B 93, 177–181 (2008). [CrossRef]

] and extended in Ref. [19

19. D. Barchiesi, N. Lidgi-Guigui, and M. Lamy de la Chapelle, “Functionalization layer influence on the sensitivity of surface plasmon resonance (SPR) biosensor,” Opt. Commun. 285, 1619–1623 (2012). [CrossRef]

].

In this case, the aluminium oxyde is supposed to be an homogeneous layer of thickness e3, above the aluminium of thickness e2 with e2 + e3 = e. The following material hypothesis are successively investigated:
  • H2a The bulk complex relative permittivities ε2 = εAl and ε3 = εAl2O3 can be used. The vector of unknown parameters is x(t) = (e2, e3, εV).
  • H2b The complex relative permittivity ε2 = εAl is unknown as it depends on the mode of deposition and on the thickness of the layer. The vector of unknown parameters is x(t) = (e2, e3, εV, εAl = ε2).

3. Numerical fit of the experimental data

In computations, the imaginary part of the permittivity ε2 is only due to the contribution of aluminium. In models H1a, H1c, H1d, and H2a, the bulk value of the relative permittivities of Aluminium and Aluminium oxyde are used. The value given in Ref. [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

] is εAl = (0.79 + 5.3ι)2 = −27.6 + 8.39ι, differs strongly from Palik’s one: εAl = (0.958 + 6.690ι)2 = −43.8 +12.8ι [20

20. E. D. Palik, Handbook of Optical Constants (Academic Press Inc., 1985).

]. The relative permittivity of aluminium oxide is also subject to variations: εAl2O3 = 1.772 = 3.13 [20

20. E. D. Palik, Handbook of Optical Constants (Academic Press Inc., 1985).

], εAl2O3 = 1.72 = 2.89 [21

21. Z. W. Zhao, B. K. T. abd L. Huang, S. Lau, and J. X. Gao, “Influence of thermal annealing on optical properties and structure of aluminium oxide thin films by filtered cathodic vacuum arc,” Opt. Mater. 27, 465–469 (2004). [CrossRef]

]. Therefore, computations using all four combinations of these results help to chose between these values. The best fits are obtained with εAl = (0.958 + 6.690ι)2 = −43.8 + 12.8ι and εAl2O3 = 1.772 = 3.13 [20

20. E. D. Palik, Handbook of Optical Constants (Academic Press Inc., 1985).

].

Figures 25 are the superimposition of the experimental data retrieved from Ref. [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

] (circles) and the computed reflectance from Eq. 4 and 9 (plain curves), for the best parameter set obtained with the models mentioned above.

Fig. 2 Experimental data from Ref. [1] for an evaluation of the thickness of the deposition h1 = 2.5 nm (circles) and computed data for the best parameters (see Tab. 1).
Fig. 3 Experimental data from Ref. [1] for an evaluation of the thickness of the deposition h1 = 8.0 nm (circles) and computed data for the best parameters (see Tab. 1).
Fig. 4 Experimental data from Ref. [1] for an evaluation of the thickness of the deposition h1 = 12.5 nm (circles) and computed data for the best parameters (see Tab. 1).
Fig. 5 Experimental data from Ref. [1] for an evaluation of the thickness of the deposition h1 = 19.0 nm (circles) and computed data for the best parameters (see Tab. 1).

The values obtained from the PSO least square fit of the experimental data seem to be in agreement but a more careful study is required to select the best model for each sample, by benching the fitness, the optical index of the prism and the thicknesses in Tab. 1.

Table 1. Fitness Function F (Eq. 1), the Best Optical Index of the Prism n1, the Best Thickness e Corresponding to hi, the Indicative Thickness, and the Corresponding Relative Permittivity ε2 of the Layer*

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Table 1 gives the best parameters for the four thicknesses h1 in the experiments [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

]: h1 ≈ 2.5 nm, 8 nm, 12.5 nm and 19 nm. The best fit is usually obtained for the minimum of the fitness function, but the corresponding thickness should also be realistic, and therefore close to hi. Our numerical study shows that the best geometrical and material parameters are highly sensitive to the model, and therefore, the agreement between the best and the indicative thickness hi is a criterion of quality of the model.

The value of the optical characteristic of the prism εV is critical to get the correct position of the slope change in the curves (between 40° and 50°) and therefore, the dispersion of the optical index of the prism is slightly dependent on the model. For example, Tab. 1 reveals that both the Geometrical Effective Medium Approximation (H1c) and the Maxwell-Garnett (H1d) models give comparable parameters but the best thickness from these two models are far from the indicative thickness hi excepted for the thinner sample. Therefore, a specific discussion seems to be necessary for each sample.

h12.5 nm. The best optical index of the prism is the same for all models. The best fit is obtained apparently for the two layers models (H2a and H2b). However, for these models, the best thickness includes a thick layer of aluminium oxyde. Surprisingly the worse fitness function (H1c and H1d) corresponds to a thickness closest to the experimental estimation h1. For this model, the Bruggeman and the Maxwell-Garnett formalisms are used and therefore, the inclusion medium and the host medium are both supposed to be dispersed in an homogenized composite medium [22

22. W. S. Weiglhofer, A. Lakhtakia, and B. Michel, “Maxwell garnett and bruggeman formalisms for a particulate composite with bianisotropic host medium,” Microw. Opt. Technol. Lett. 15, 263–266 (1997). [CrossRef]

]. Both models H1c and H1d give an effective relative permittivity of the medium which differs from the bulk one. This deviation can be explained by the presence of oxyde mixed in the metal layer. The fraction of aluminium oxyde is about 34% and therefore the real part of the effective index is greater than this of bulk. Moreover, the imaginary part of the optical index is half of this of bulk. The inclusion of oxyde modifies the absorption of the material and therefore decreases its electric conductivity. the behavior of the relative permittivity (H2b) supports this conclusion. For this very small thickness of aluminium, these results show that the hypothesis of oxydation is relevant.

h18 nm. The variations of the fitness function are important. The best fit is obtained with the two layers model, leaving free the relative permittivity of gold. In this case, the thickness of aluminium is 5.2 nm and the thickness of Al2O3 is 3.2 nm. The best relative permittivity of Aluminium is close to the bulk one, but the best results are obtained for a free relative permittivity of aluminium (H1b and H2a). The corresponding relative permittivities could be compared to the bulk values also indicated in the Table [20

20. E. D. Palik, Handbook of Optical Constants (Academic Press Inc., 1985).

]. The real part of the result of the fit is close the Palik’s one, whereas the imaginary part is close to Turbadar’s one. The increase of the real part of the optical index can only be explained by a transition between the cases of the very small thickness (h1 ≈ 2.5 nm), where the effective medium is less metallic than pure aluminium.

h119 nm. Whatever the model is, the fits of the experimental results have about the same quality: the values of F are close to each other. Therefore the quality of the fit is not sufficient to determine the best model and therefore to conclude on the material nature of the layer, even if the performance of H1a could suggest that the layer can be considered as pure aluminium. On the other hand, the computed thickness can be compared to the indicative hi and therefore, three models could be selected: H1a (the pure metal layer), H2a and H2b (the thickness of oxyde being negligible). The Maxwell-Garnett and the Bruggeman models are not acceptable for this thickness. Under H1d, the best fraction of oxyde is lower than 2%. Therefore, for the sample of thickness h1 ≈ 19 nm, the layer can be considered as pure aluminium. This result is confirmed by the performance of the simplest model H1a, where a single layer of Aluminium is considered, with the relative permittivity of bulk.

The oxydation of Aluminium seems to be a good explanation of the discrepancies between the experimental data and the original computed curves [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

]. The real part of the effective index of the layer is much greater than that of pure aluminum, for small thicknesses. If the thickness is greater than 8 nm, its behavior tends to that of the bulk metal. The imaginary part of the relative permittivity decreases drastically for small thickness. This last behavior is coherent with the hypothesis of inclusions of the oxyde in the metal which decrease its electric conductivity. The increase of the real part in the present case confirms that the possible cristalline structure of aluminum in thin layer cannot be invoked. This material property of nanostructures tends actually to decrease the real part of the optical index [23

23. A. Vial, T. Laroche, and M. Roussey, “Crystalline structure’s influence on the near-field optical properties of single plasmonic nanowires,” Appl. Phys. Lett. 91, 123101 (2007).

]. Therefore, the hypothesis of aluminium oxydation is relevant.

4. Physical discussion

4.1. Perturbation approach

The explanation of the dependence of the reflectance curves with the thickness can now be made. For simplicity, the single layer only is under consideration. The exponential fe = exp(2ιew2) in Eq. 4, in the range of incidence angles: Φg ∈ [25°,65°] governs the physical discussion. Table 2 gives the minima and the maxima of the real and imaginary parts of the function fe.

Table 2. Rounded Numerical Values of fe = exp(2ιew2) Involved in the Reflectance Formula (Eq. 4 and 9)

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  • The very small thickness (e = 2 nm). The first column in Tab. 2 shows that fe is close to 1 and the series of the reflectance can be written:
    Rt=|r12+r231+r12r23DL0+r23(1(r12)2)(1+r12r23)2(fe1)+o(fe1)2|2.|1(r01)2|2
    (10)
    Consequently, two opposite cases can be considered: the very small thickness (h1 = 2.5 nm) where fe ≈ 1 and the small thickness (e = 19.8 nm) where fe ≈ 0, and between then, the intermediate thicknesses 7.7 and 15.8 nm.

    The zero order of the series is predominant and the shape of the curves are hardly dependent on the thickness e. The reflectance is characterized by a drastic change when the angle of illumination overpass the critical angle Phigc=arcsin(ε3/εV)40°. In this case, the plasmon resonance effect is not dominant, even if the effective permittivity of the layer is that of a metal. DL0 is independent on the thickness but involves the relative permittivities of the substrate, the layer and the above medium.

  • The small thickness (e > 20 nm). The last column in Tab. 2 shows that fe is close to 0. This case has been considered in a previous paper [24

    24. A. Otto, “Spectroscopy of surface polaritons by attenuated total reflection” in Optical properties of solids - new developments (North Holland, 1974), pp. 679–729.

    ]. The discussion presented here, makes the link between the resonance, and the series deduced from polynomial division of the numerator by the denominator in the reflectance formula. The reflectance can be approximated:
    Rt=|r12+r23.(1(r12)2)feDL1+o(fe)2|2.|1(r01)2|2
    (11)

    The zero order term does not able to describe the rapid change of slope of the reflectance in p polarization (the sign of the plasmon resonance), on the contrary of the higher order term of the series. This factor DL1 is the product of the Fresnel reflection coefficient of the interface 2 – 3 ( r23) multiplied by (1(r12)2). This last term can be expressed by the product of the Fresnel transmission coefficient of the interfaces 1 – 2 and 2 – 1. DL1 has a resonance behavior as shown in Fig. 6.

Figures 6 and 7 illustrate the closeness of DL0 (resp DL1) and the reflectance curves in (p) and (s) polarization, for very small (resp. small) thickness. The chosen parameters are typical of the results in Tab. 1 for a single layer. Even if the permittivity of the layer is characteristic of a metal in the case of very small thickness, the plasmon resonance cannot be observed. On the contrary, for a thickness around 20 nm, the plasmon can be observed. Consequently, the thickness plays a key role in the plasmon resonance.

Fig. 6 Computed reflectance Rt for p polarization (a) and s polarization (b), in the case of very small thickness. The result is compared to DL0 and DL1.
Fig. 7 Computed reflectance Rt for p polarization (a) and s polarization (b), in the case of small thickness. The result is compared to DL0 and DL1.

Figures 8 and 9 show the transition between these two opposite cases. The plasmon resonance appears in Fig. 9 but not in Fig. 8.

Fig. 8 Computed reflectance Rt for p polarization (a) and s polarization (b), in the case of intermediate thickness. The result is compared to DL0 and DL1.
Fig. 9 Computed reflectance Rt for p polarization (a) and s polarization (b), in the case of intermediate thickness. The result is compared to DL0 and DL1.

Therefore, the thickness is a critical parameters for the surface plasmon resonance. In the case of nanometric thickness, the plasmon cannot be excited and the ultra thin layer modifies the reflectance in a quasi on-off manner. To generate a plasmon resonance, the thickness of aluminium should reach a given threshold, which depends on the deposition mode and on the material. In this case, the shape of the reflectance is strongly linked to the thickness of metal. A S matrix formulation can help to characterize the plasmon resonance.

4.2. The S matrix and the plasmon resonance

The plasmon resonance has been fully described by Otto in Ref. [3

3. A. Otto and W. Sohler, “Modification of the total reflection modes in a dielectric film by one metal boundary,” Opt. Commun. 3, 254–258 (1971). [CrossRef]

] and in [25

25. H. Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings (Springer-Verlag, 1988).

]. The theoretical dispersion relation of plasmons is commonly obtained without illumination, a linear system relating the amplitudes of the fields in all materials, being deduced. Therefore, this homogenous system admits non trivial solution if the determinant of the associated matrix is equal to zero [25

25. H. Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings (Springer-Verlag, 1988).

28

28. A. Kolomenskii, P. Gershon, and H. Schuessler, “Sensitivity and detection limit of concentration and absorption measurements by laser-induced surface-plasmon resonance,” Appl. Opt. 36, 6539–6547 (1997). [CrossRef]

]. This approach is the general application of a general law on resonances, which claims that it corresponds to obtain something from nothing. However, the properties of the S matrix in the plasmon resonance conditions have nevertheless rarely been specified even if this formalism is broadly used to describe resonances in quantum mechanics, acoustics. . . [13

13. D. Barchiesi, “Optimization of biosensors,” in New Perspectives in biosensors technology and applications, P. A. Serra, ed. (INTECH Open Access, Rijeka, Croatia, 2011), pp. 105–126.

].

Fig. 10 Experimental data, real and imaginary part of the determinant D(S−1). The parameters are given in Tab. 1 for the model H1a.
Fig. 11 Experimental data, real and imaginary part of the determinant D(S−1). The parameters are given in Tab. 1 for the model H1a.

Figure 10 shows that the real part of the determinant does not vanish. The change of slope of the reflectance curve is due to the vanishing of the imaginary part of D(S−1). This behavior explains that the shape of the curves is not characteristic of the plasmon resonance, on the contrary of the curves in Fig. 11, for which the real part and the imaginary part of D(S−1) vanish for about the same angle Φg.

5. Conclusion

In this paper, the retrieval of unknown experimental parameters in [1

1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

] has been done with the Particle Swarm Optimization method. The oxydation of the aluminium layer has helped to explain the obtained results, especially in the case of very thin layers. The shape of the reflectance curves in p polarization has been explained in the cases of very thin nanometric layers and of thin layers with thickness greater than about 10 nm. For very thin layer, the shape of the reflectance curve is hardly dependent on the thickness. In the case of thicker layer, the resonance behavior of the first order term of the series, assuming exp(2ιew2) close to 0, can explain the reflectance change of slope and the plasmon resonance. The determinant of the inverse of the S matrix helps to characterize the plasmon resonance. The oxydation of very thin layer could be an explanation of the shape of the reflectance in Kretschmann configuration. The proposed particle swarm method could be applied to thin layers made of other metals and to other inverse problem of experimental studies as phase recovering [33

33. P. Sandoz, T. Gharbi, and G. Tribillon, “Phase-shifting methods for interferometers using laser-diode frequency-modulation,” Opt. Commun. 132, 227–231 (1996). [CrossRef]

], sensors [34

34. A. Courteville, T. Gharbi, and J. Y. Cornu, “Noncontact MMG sensor based on the optical feedback effect in a laser diode,” J. Biomed. Opt. 3, 281–285 (1998). [CrossRef]

] or theoretical studies where the best parameters are searched [35

35. B. Guizal and D. Felbacq, “Electromagnetic beam diffraction by a finite strip grating,” Opt. Commun. 165, 1–6 (1999). [CrossRef]

, 36

36. F. I. Baida, Y. Poujet, J. Salvi, D. Van Labeke, and B. Guizal, “Extraordinary transmission beyond the cut-off through sub-λ annular aperture arrays,” Opt. Commun. 282, 1463–1466 (2009). [CrossRef]

].

Acknowledgments

The first proposal to put to the front the results by Turbadar, and to explain them is due to Andreas Otto. The author wishes to thank Andreas for having provided the idea of this study, and for discussions on this stimulating subject. The ethics about the inclusion of authors according to their participation in the writing of the paper, led him to not accept to be co-author.

This work was supported by the “ Conseil Régional de Champagne Ardenne”, the “ Conseil Général de l’Aube” and the Nanoantenna European Project (FP7 Health-F5-2009-241818).

References and links

1.

T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc. 73, 40–44 (1959). [CrossRef]

2.

E. Kretschmann, “Die bestimmung optischer konstanten von metallen durch anregung von oberflachenplasmaschwingungen,” Z. Phys. 241, 313–324 (1971). [CrossRef]

3.

A. Otto and W. Sohler, “Modification of the total reflection modes in a dielectric film by one metal boundary,” Opt. Commun. 3, 254–258 (1971). [CrossRef]

4.

D. Macias and D. Barchiesi, “Identification of unknown experimental parameters from noisy apertureless scanning near-field optical microscope data with an evolutionary procedure,” Opt. Lett. 30, 2557–2559 (2005). [CrossRef] [PubMed]

5.

J. Kennedy and R. Eberhart, “Particle swarm optimization,” in Proceedings of IEEE International Conference on Neural Networks (IV) (IEEE, 1995), pp. 1942–1948.

6.

S. Kessentini, D. Barchiesi, T. Grosges, L. Giraud-Moreau, and M. Lamy de la Chapelle, “Adaptive non-uniform particle swarm application to plasmonic design,” Int. J. Appl. Metaheuristic Comput. 2, 18–28 (2011). [CrossRef]

7.

S. Kessentini, D. Barchiesi, T. Grosges, and M. Lamy de la Chapelle, “Particle swarm optimization and evolutionary methods for plasmonic biomedical applications,” in Proceedings of IEEE Congress on Evolutionary Computation (CEC) (IEEE, 2010), pp. 2315–2320.

8.

M. Clerc, “A method to improve standard PSO,” Tech. Rep. DRAFT MC2009-03-13, France Telecom R&D (2009).

9.

H. P. Schwefel, Evolution and Optimum Seeking (John Wiley & Sons Inc., 1995).

10.

D. Macías, A. Vial, and D. Barchiesi, “Application of evolution strategies for the solution of an inverse problem in near-nield optics,” J. Opt. Soc. Am. A 21, 1465–1471 (2004). [CrossRef]

11.

D. Barchiesi, “Adaptive non-uniform, hyper-ellitist evolutionary method for the optimization of plasmonic biosensors,” in “Proceedings of IEEE International Conference on Computers & Industrial Engineering (CIE)” (IEEE, 2009), 542–547.

12.

E. Kretschmann, “The ATR method with focused light - application to guided waves on a grating,” Opt. Commun. 23, 41–44 (1978). [CrossRef]

13.

D. Barchiesi, “Optimization of biosensors,” in New Perspectives in biosensors technology and applications, P. A. Serra, ed. (INTECH Open Access, Rijeka, Croatia, 2011), pp. 105–126.

14.

D. A. G. Bruggeman, “Berechnung verschiedener physikalischer konstanten von heterogenen substantzen. i. dielektrizitätskonstanten und leifähigkeiten der misckörper aus isotropen substanzen,” Ann. Phys. (Leipzig) 24, 636–679 (1935).

15.

A. J. Abu El-Haija, “Effective medium approximation for the effective optical constants of a bilayer and a multilayer structure based on the characteristic matrix technique,” J. Appl. Phys. 93, 2590–2594 (2003). [CrossRef]

16.

W. R. Tinga, W. A. G. Voss, and D. F. Blossey, “Generalized approach to multiphase dielectric mixture theory,” J. Appl. Phys. 44, 3897–3903 (1973). [CrossRef]

17.

S. W. Dean, D. Knotkova, and K. Kreislovain ISOCORRAG International Atmospheric Exposure Program: Summary of Results, DS71 (ASTM International, 2010).

18.

D. Barchiesi, D. Macías, L. Belmar-Letellier, D. Van Labeke, M. Lamy de la Chapelle, T. Toury, E. Kremer, L. Moreau, and T. Grosges, “Plasmonics: Influence of the intermediate (or stick) layer on the efficiency of sensors,” Appl. Phys. B 93, 177–181 (2008). [CrossRef]

19.

D. Barchiesi, N. Lidgi-Guigui, and M. Lamy de la Chapelle, “Functionalization layer influence on the sensitivity of surface plasmon resonance (SPR) biosensor,” Opt. Commun. 285, 1619–1623 (2012). [CrossRef]

20.

E. D. Palik, Handbook of Optical Constants (Academic Press Inc., 1985).

21.

Z. W. Zhao, B. K. T. abd L. Huang, S. Lau, and J. X. Gao, “Influence of thermal annealing on optical properties and structure of aluminium oxide thin films by filtered cathodic vacuum arc,” Opt. Mater. 27, 465–469 (2004). [CrossRef]

22.

W. S. Weiglhofer, A. Lakhtakia, and B. Michel, “Maxwell garnett and bruggeman formalisms for a particulate composite with bianisotropic host medium,” Microw. Opt. Technol. Lett. 15, 263–266 (1997). [CrossRef]

23.

A. Vial, T. Laroche, and M. Roussey, “Crystalline structure’s influence on the near-field optical properties of single plasmonic nanowires,” Appl. Phys. Lett. 91, 123101 (2007).

24.

A. Otto, “Spectroscopy of surface polaritons by attenuated total reflection” in Optical properties of solids - new developments (North Holland, 1974), pp. 679–729.

25.

H. Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings (Springer-Verlag, 1988).

26.

M. L. Nesterov, A. V. Kats, and S. K. Turitsyn, “Extremely short-length surface plasmon resonance devices,” Opt. Express 16, 20227–20240, (2008). [CrossRef] [PubMed]

27.

A. V. Zayats, I. I. Smolyaninov, and A. A. Maradudin, “Nano-optics of surface plasmon polaritons,” Phys. Rep. 408, 131–314 (2005). [CrossRef]

28.

A. Kolomenskii, P. Gershon, and H. Schuessler, “Sensitivity and detection limit of concentration and absorption measurements by laser-induced surface-plasmon resonance,” Appl. Opt. 36, 6539–6547 (1997). [CrossRef]

29.

D. Y. K. Ko and J. R. Sambles, “Scattering matrix method for propagation of radiation in stratified media: Attenuated total reflection studies of liquid crystals,” J. Opt. Soc. Am. A 5, 1863–1866 (1988). [CrossRef]

30.

J. M. Vigoureux, “Polynomial formulation of reflection and transmission by stratified planar structures,” J. Opt. Soc. Am. A 8, 1697–1701 (1991). [CrossRef]

31.

L. Li, “Formulation and comparison of two recursive matrix algorithms for modeling layered diffraction gratings,” J. Opt. Soc. Am. A 13, 1024–1035 (1996). [CrossRef]

32.

D. Barchiesi, E. Kremer, V. Mai, and T. Grosges, “A Poincaré’s approach for plasmonics: the plasmon localization,” J. Microscopy 229, 525–532 (2008). [CrossRef]

33.

P. Sandoz, T. Gharbi, and G. Tribillon, “Phase-shifting methods for interferometers using laser-diode frequency-modulation,” Opt. Commun. 132, 227–231 (1996). [CrossRef]

34.

A. Courteville, T. Gharbi, and J. Y. Cornu, “Noncontact MMG sensor based on the optical feedback effect in a laser diode,” J. Biomed. Opt. 3, 281–285 (1998). [CrossRef]

35.

B. Guizal and D. Felbacq, “Electromagnetic beam diffraction by a finite strip grating,” Opt. Commun. 165, 1–6 (1999). [CrossRef]

36.

F. I. Baida, Y. Poujet, J. Salvi, D. Van Labeke, and B. Guizal, “Extraordinary transmission beyond the cut-off through sub-λ annular aperture arrays,” Opt. Commun. 282, 1463–1466 (2009). [CrossRef]

OCIS Codes
(000.4430) General : Numerical approximation and analysis
(100.3190) Image processing : Inverse problems
(240.0310) Optics at surfaces : Thin films
(240.6680) Optics at surfaces : Surface plasmons

ToC Category:
Optics at Surfaces

History
Original Manuscript: February 27, 2012
Revised Manuscript: March 27, 2012
Manuscript Accepted: March 27, 2012
Published: April 3, 2012

Citation
Dominique Barchiesi, "Numerical retrieval of thin aluminium layer properties from SPR experimental data," Opt. Express 20, 9064-9078 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-8-9064


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References

  1. T. Turbadar, “Complete absorption of light by thin metal films,” Proc. Phys. Soc.73, 40–44 (1959). [CrossRef]
  2. E. Kretschmann, “Die bestimmung optischer konstanten von metallen durch anregung von oberflachenplasmaschwingungen,” Z. Phys.241, 313–324 (1971). [CrossRef]
  3. A. Otto and W. Sohler, “Modification of the total reflection modes in a dielectric film by one metal boundary,” Opt. Commun.3, 254–258 (1971). [CrossRef]
  4. D. Macias and D. Barchiesi, “Identification of unknown experimental parameters from noisy apertureless scanning near-field optical microscope data with an evolutionary procedure,” Opt. Lett.30, 2557–2559 (2005). [CrossRef] [PubMed]
  5. J. Kennedy and R. Eberhart, “Particle swarm optimization,” in Proceedings of IEEE International Conference on Neural Networks (IV) (IEEE, 1995), pp. 1942–1948.
  6. S. Kessentini, D. Barchiesi, T. Grosges, L. Giraud-Moreau, and M. Lamy de la Chapelle, “Adaptive non-uniform particle swarm application to plasmonic design,” Int. J. Appl. Metaheuristic Comput.2, 18–28 (2011). [CrossRef]
  7. S. Kessentini, D. Barchiesi, T. Grosges, and M. Lamy de la Chapelle, “Particle swarm optimization and evolutionary methods for plasmonic biomedical applications,” in Proceedings of IEEE Congress on Evolutionary Computation (CEC) (IEEE, 2010), pp. 2315–2320.
  8. M. Clerc, “A method to improve standard PSO,” Tech. Rep. DRAFT MC2009-03-13, France Telecom R&D (2009).
  9. H. P. Schwefel, Evolution and Optimum Seeking (John Wiley & Sons Inc., 1995).
  10. D. Macías, A. Vial, and D. Barchiesi, “Application of evolution strategies for the solution of an inverse problem in near-nield optics,” J. Opt. Soc. Am. A21, 1465–1471 (2004). [CrossRef]
  11. D. Barchiesi, “Adaptive non-uniform, hyper-ellitist evolutionary method for the optimization of plasmonic biosensors,” in “Proceedings of IEEE International Conference on Computers & Industrial Engineering (CIE)” (IEEE, 2009), 542–547.
  12. E. Kretschmann, “The ATR method with focused light - application to guided waves on a grating,” Opt. Commun.23, 41–44 (1978). [CrossRef]
  13. D. Barchiesi, “Optimization of biosensors,” in New Perspectives in biosensors technology and applications, P. A. Serra, ed. (INTECH Open Access, Rijeka, Croatia, 2011), pp. 105–126.
  14. D. A. G. Bruggeman, “Berechnung verschiedener physikalischer konstanten von heterogenen substantzen. i. dielektrizitätskonstanten und leifähigkeiten der misckörper aus isotropen substanzen,” Ann. Phys. (Leipzig)24, 636–679 (1935).
  15. A. J. Abu El-Haija, “Effective medium approximation for the effective optical constants of a bilayer and a multilayer structure based on the characteristic matrix technique,” J. Appl. Phys.93, 2590–2594 (2003). [CrossRef]
  16. W. R. Tinga, W. A. G. Voss, and D. F. Blossey, “Generalized approach to multiphase dielectric mixture theory,” J. Appl. Phys.44, 3897–3903 (1973). [CrossRef]
  17. S. W. Dean, D. Knotkova, and K. Kreislovain ISOCORRAG International Atmospheric Exposure Program: Summary of Results, DS71 (ASTM International, 2010).
  18. D. Barchiesi, D. Macías, L. Belmar-Letellier, D. Van Labeke, M. Lamy de la Chapelle, T. Toury, E. Kremer, L. Moreau, and T. Grosges, “Plasmonics: Influence of the intermediate (or stick) layer on the efficiency of sensors,” Appl. Phys. B93, 177–181 (2008). [CrossRef]
  19. D. Barchiesi, N. Lidgi-Guigui, and M. Lamy de la Chapelle, “Functionalization layer influence on the sensitivity of surface plasmon resonance (SPR) biosensor,” Opt. Commun.285, 1619–1623 (2012). [CrossRef]
  20. E. D. Palik, Handbook of Optical Constants (Academic Press Inc., 1985).
  21. Z. W. Zhao, B. K. T. abd L. Huang, S. Lau, and J. X. Gao, “Influence of thermal annealing on optical properties and structure of aluminium oxide thin films by filtered cathodic vacuum arc,” Opt. Mater.27, 465–469 (2004). [CrossRef]
  22. W. S. Weiglhofer, A. Lakhtakia, and B. Michel, “Maxwell garnett and bruggeman formalisms for a particulate composite with bianisotropic host medium,” Microw. Opt. Technol. Lett.15, 263–266 (1997). [CrossRef]
  23. A. Vial, T. Laroche, and M. Roussey, “Crystalline structure’s influence on the near-field optical properties of single plasmonic nanowires,” Appl. Phys. Lett.91, 123101 (2007).
  24. A. Otto, “Spectroscopy of surface polaritons by attenuated total reflection” in Optical properties of solids - new developments (North Holland, 1974), pp. 679–729.
  25. H. Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings (Springer-Verlag, 1988).
  26. M. L. Nesterov, A. V. Kats, and S. K. Turitsyn, “Extremely short-length surface plasmon resonance devices,” Opt. Express16, 20227–20240, (2008). [CrossRef] [PubMed]
  27. A. V. Zayats, I. I. Smolyaninov, and A. A. Maradudin, “Nano-optics of surface plasmon polaritons,” Phys. Rep.408, 131–314 (2005). [CrossRef]
  28. A. Kolomenskii, P. Gershon, and H. Schuessler, “Sensitivity and detection limit of concentration and absorption measurements by laser-induced surface-plasmon resonance,” Appl. Opt.36, 6539–6547 (1997). [CrossRef]
  29. D. Y. K. Ko and J. R. Sambles, “Scattering matrix method for propagation of radiation in stratified media: Attenuated total reflection studies of liquid crystals,” J. Opt. Soc. Am. A5, 1863–1866 (1988). [CrossRef]
  30. J. M. Vigoureux, “Polynomial formulation of reflection and transmission by stratified planar structures,” J. Opt. Soc. Am. A8, 1697–1701 (1991). [CrossRef]
  31. L. Li, “Formulation and comparison of two recursive matrix algorithms for modeling layered diffraction gratings,” J. Opt. Soc. Am. A13, 1024–1035 (1996). [CrossRef]
  32. D. Barchiesi, E. Kremer, V. Mai, and T. Grosges, “A Poincaré’s approach for plasmonics: the plasmon localization,” J. Microscopy229, 525–532 (2008). [CrossRef]
  33. P. Sandoz, T. Gharbi, and G. Tribillon, “Phase-shifting methods for interferometers using laser-diode frequency-modulation,” Opt. Commun.132, 227–231 (1996). [CrossRef]
  34. A. Courteville, T. Gharbi, and J. Y. Cornu, “Noncontact MMG sensor based on the optical feedback effect in a laser diode,” J. Biomed. Opt.3, 281–285 (1998). [CrossRef]
  35. B. Guizal and D. Felbacq, “Electromagnetic beam diffraction by a finite strip grating,” Opt. Commun.165, 1–6 (1999). [CrossRef]
  36. F. I. Baida, Y. Poujet, J. Salvi, D. Van Labeke, and B. Guizal, “Extraordinary transmission beyond the cut-off through sub-λ annular aperture arrays,” Opt. Commun.282, 1463–1466 (2009). [CrossRef]

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