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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 21 — Oct. 21, 2013
  • pp: 25307–25315
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Triple-layer Fabry-Perot absorber with near-perfect absorption in visible and near-infrared regime

Shiwei Shu, Zhe Li, and Yang Yang Li  »View Author Affiliations


Optics Express, Vol. 21, Issue 21, pp. 25307-25315 (2013)
http://dx.doi.org/10.1364/OE.21.025307


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Abstract

A simple absorber design which enables near-perfect absorption in the visible and near-infrared regions is presented. The absorber is an unpatterned metal/dielectric/metal triple-layer, e.g., a 20 nm-thick metal film as the top layer, a 250 nm-thick dielectric film as the middle layer, and a 200 nm-thick metal film as the bottom layer. It was found that the high-efficiency absorption at specific wavelengths is mainly due to the Fabry-Perot (FP) resonances in the dielectric middle layer which result in trapping of the resonant light in the middle layer and thus enhanced absorption efficiency.

© 2013 Optical Society of America

1. Introduction

Light absorbers have attracted much attention for their great promise in a wide range of applications, such as solar cells, photodetectors, sensors, bolometers, nanoimaging devices and thermal emitters [1

1. N. I. Landy, S. Sajuyigbe, J. J. Mock, D. R. Smith, and W. J. Padilla, “Perfect Metamaterial Absorber,” Phys. Rev. Lett. 100(20), 207402 (2008). [CrossRef]

5

5. B. X. Zhang, Y. H. Zhao, Q. Z. Hao, B. Kiraly, I. C. Khoo, S. F. Chen, and T. J. Huang, “Polarization-independent dual-band infrared perfect absorber based on a metal-dielectric-metal elliptical nanodisk array,” Opt. Express 19(16), 15221–15228 (2011). [CrossRef]

]. Since Landy et al. proposed in 2008 to achieve perfect absorption by using meta-materials with effect impedance equaling to free space, various kinds of super absorber have been proposed and studied [1

1. N. I. Landy, S. Sajuyigbe, J. J. Mock, D. R. Smith, and W. J. Padilla, “Perfect Metamaterial Absorber,” Phys. Rev. Lett. 100(20), 207402 (2008). [CrossRef]

7

7. J. M. Hao, J. Wang, X. L. Liu, W. J. Padilla, L. Zhou, and M. Qiu, “High performance optical absorber based on a plasmonic metamaterial,” Appl. Phys. Lett. 96(25), 251104 (2010). [CrossRef]

]. However, the majority of current designs focus on building an elaborate metallic pattern on a thin (e.g., 20 nm) dielectric spacer film which is attached to a thick metal layer. It is worth noting that most reported absorber designs contain miniature and elaborate structural features (especially for the top metallic layer), setting manufacturing obstacles for the practical applications of super absorbers. In fact, currently most super absorbers working in the visible and near-IR regime are fabricated on a small area using expensive nanofabrication techniques, e.g., the e-beam lithography. Lately, simpler designs of perfect absorber based on layered structures (e.g., a lossy dielectric film on a metal film) have been proposed [8

8. M. A. Kats, D. Sharma, J. Lin, P. Genevet, R. Blanchard, Z. Yang, M. M. Qazilbash, D. N. Basov, S. Ramanathan, and F. Capasso, “Ultra-thin perfect absorber employing a tunable phase change material,” Appl. Phys. Lett. 101(22), 221101 (2012). [CrossRef]

,9

9. S. Shu and Y. Y. Li, “Metallic rugate structures for near-perfect absorbers in visible and near-infrared regions,” Opt. Lett. 37(17), 3495–3497 (2012). [CrossRef]

]. On the other hand, it should be pointed out that a simple triple-layered structure invented in 1952, the Salisbury screen (SS) which typically consists of a metallic ground plane, a lossless dielectric middle layer, and a thin glossy top layer [10

10. B. Munk, Frequency Selective Surfaces: Theory and Design (John Wiley & Sons, 2000).

,11

11. W. W. Salisbury, US Patent No. 2599944 (1952).

], was one of the first near-perfect absorbers, originally designed for the military radar waves. However, the SS was soon surpassed by other designs for the disadvantage of bulky thickness. Here we propose a thin-film type of SS absorber working in visible and near-infrared regime, possessing great optical flexibility and fabrication convenience.

2. Structure model

Fig. 1 Proposed absorber design with an Ag/dielectric/Ag structure in visible and near-IR region. The incident angle is labeled as θ.
The absorber design is schematically shown in Fig. 1, which consists of a metallic top layer, a dielectric middle layer, and a metallic bottom layer, with the respective layer thickness of d1, d2 and d3, and the respective relative permittivity of εr1, εr2 and εr3. The relative permittivity of metals is described using the Lortenz-Drude model [12

12. P. B. Johnson and R. W. Christy, “Optical Constants of the Noble Metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]

,13

13. M. A. Ordal, L. L. Long, R. J. Bell, S. E. Bell, R. R. Bell, R. W. Alexander Jr, and C. A. Ward, “Optical-Properties of the Metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the Infrared and Far Infrared,” Appl. Opt. 22(7), 1099–1119 (1983). [CrossRef]

]. Unless otherwise stated, in this report, d1, d2 and d3, are set to be 20, 250, and 200 nm, respectively, εr2 is set to be 3.42, and the top and bottom layers are made of Ag.

3. Theory study

Besides the mathematical method (MM) presented above, the Transfer Matrix Method (TMM) and the Finite-Difference Time-Domain (FDTD) method (using the commercial software EastFDTD) were also used to check the accuracy of the simulation results. It was found that these three methods are in good agreement (see Fig. 3).
Fig. 3 The absorption spectra for an Ag/dielectric/Ag absorber calculated by the mathematical method (MM) presented in Section 3 (top), the TMM (middle), and the FDTD method (bottom).
It should be pointed out that, for calculating structures with thick bottom layer thicknesses, the MM requires less computation time comparing to the numerical methods.

4. Results and discussion

The absorber structures with both the top and bottom metal layers made of the same type of metal, including Au, Ag, Cu, Al, Ni, are simulated (see Fig. 4).
Fig. 4 Absorption spectra for the absorbers based on different metals: Au, Ag, Cu, Al and Ni.
Among the different metals tested, all show multiple absorption peaks with the 1st, 2nd and 3rd order peaks located around 1200, 600 and 400 nm, respectively. Notably, Au, Ag and Cu show sharp and near-perfect absorption peaks in the visible and NIR region, demonstrating their potential application as perfect absorbers.

It should be pointed out that the working mechanism of the perfect absorber reported here is significantly different from another type that is being intensively investigated which is also based on a metal/dielectric/metal 3-layer structure. Comparing to the one reported here, the other type of perfect absorber usually features a micro-patterned top metal and much thinner (e.g., 20 nm) middle dielectric layer. More importantly, the absorption mechanism of the other type of triple-layer absorber is mainly attributed to the electric resonance of the top metal layer and magnetic resonance created by the top and bottom metal layers, whereas the middle dielectric layer mainly serves as a spacer layer. On the contrary, the high efficiency of the absorbers reported here is mainly attributed to the FP resonance of the middle dielectric layer. Simulation of the electric field distribution over the cross-section of the absorber (see Fig. 5) reveal that (1) most light is trapped in the middle dielectric layer, and (2) the bottom metal layer not only absorbs the transmitted light, but provide a strong reflection and form a Fabry-Perot cavity for the dielectric layer.
Fig. 5 Electric field distribution over the cross-section of the absorber at 1142 nm for an Ag/dielectric/Ag structure.

To reveal the function of each layer, the optical responses of the absorber with either the top metal layer or the bottom metal layer removed were studied (see Fig. 6).
Fig. 6 Absorption spectra for an Ag/dielectric/Ag structure calculated using the FDTD method: (a) only middle and bottom layers, (b) only top and middle layers, (c) three layers.
When either the top or bottom layer is missing, only low and broadened absorption peaks are present over the entire spectrum studied. This indicates the necessities of each layer and their synergetic effects for achieving high absorption.

Fig. 9 Absorption spectra calculated by the FDTD method of an Ag/Si/Ag absorber with either the wavelength-dispersion of complex refractive index (“complex n”) of Si considered, or with εr2 set to 11.7 (“εr2=11.7”) for the entire wavelength range.
For practical purposes, it will be useful to consider that the absorber middle layer possesses a complex refractive index (with absorption coefficient) that is wavelength-dispersive. Take silicon for example, two absorption spectra of an Ag/Si/Ag absorber were simulated (see Fig. 9): one plotted using the wavelength-dispersive complex refractive index of Si [18

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

]; the other calculated with εr2 set to 11.7 for the entire wavelength range. It can be seen that with the absorption coefficient considered, lower absorption peaks with wider full width at half maximum (FWHM) are observed, possibly because the FP resonance is weakened by the lossy middle layer. The shifts of the absorption peaks are caused by the wavelength-dispersion characteristics of Si.

Study on the absorption behaviors with different incident angles show that the peak blue-shifted with increasing incident angle (see Fig. 10).
Fig. 10 Absorption spectra for TE and TM polarizations at different incident angles for an Ag/dielectric/Ag structure. The insets show angular dependence of absorption at λ = 1142 nm.
Notice that the absorption intensity significantly reduces as the incident angle increases, e.g., the intensity of the 1st order peak at 1142 nm reduces to half at 20° for TE polarization and 30° for TM polarization, suggesting the angle sensitivity of the absorbers and its potential application for directional thermal emitters.

4. Conclusion

A simple type of thin-film absorber for visible and near-IR light is theoretically studied. These absorbers feature a simple metal/dielectric/metal 3-layer structure. Different types of metals, including Ag, Au and Cu, are well-suited for constructing this type of absorber with near-perfect absorption. Mechanism study reveals that light absorption is mainly resulted from the FP resonance in the middle dielectric layer. The absorption response is found sensitive to the thicknesses of the top and middle layers and the incident angle. The simple design of the absorbers reported here indicates particularly attractive manufacturing convenience for low-cost mass production, holding great promise for various practical applications.

Acknowledgment

This work was supported by the National Natural Science Foundation of China (Project 51202206), and the City University of Hong Kong (Projects 9667070 and 7003039).

References and links

1.

N. I. Landy, S. Sajuyigbe, J. J. Mock, D. R. Smith, and W. J. Padilla, “Perfect Metamaterial Absorber,” Phys. Rev. Lett. 100(20), 207402 (2008). [CrossRef]

2.

M. Diem, T. Koschny, and C. M. Soukoulis, “Wide-angle perfect absorber/thermal emitter in the terahertz regime,” Phys. Rev. B 79(3), 033101 (2009). [CrossRef]

3.

J. J. Greffet, R. Carminati, K. Joulain, J. P. Mulet, S. P. Mainguy, and Y. Chen, “Coherent emission of light by thermal sources,” Nature 416(6876), 61–64 (2002). [CrossRef]

4.

N. Liu, M. Mesch, T. Weiss, M. Hentschel, and H. Giessen, “Infrared Perfect Absorber and Its Application As Plasmonic Sensor,” Nano Lett. 10(7), 2342–2348 (2010). [CrossRef]

5.

B. X. Zhang, Y. H. Zhao, Q. Z. Hao, B. Kiraly, I. C. Khoo, S. F. Chen, and T. J. Huang, “Polarization-independent dual-band infrared perfect absorber based on a metal-dielectric-metal elliptical nanodisk array,” Opt. Express 19(16), 15221–15228 (2011). [CrossRef]

6.

C. G. Hu, Z. Y. Zhao, X. N. Chen, and X. G. Luo, “Realizing near-perfect absorption at visible frequencies,” Opt. Express 17(13), 11039–11044 (2009). [CrossRef]

7.

J. M. Hao, J. Wang, X. L. Liu, W. J. Padilla, L. Zhou, and M. Qiu, “High performance optical absorber based on a plasmonic metamaterial,” Appl. Phys. Lett. 96(25), 251104 (2010). [CrossRef]

8.

M. A. Kats, D. Sharma, J. Lin, P. Genevet, R. Blanchard, Z. Yang, M. M. Qazilbash, D. N. Basov, S. Ramanathan, and F. Capasso, “Ultra-thin perfect absorber employing a tunable phase change material,” Appl. Phys. Lett. 101(22), 221101 (2012). [CrossRef]

9.

S. Shu and Y. Y. Li, “Metallic rugate structures for near-perfect absorbers in visible and near-infrared regions,” Opt. Lett. 37(17), 3495–3497 (2012). [CrossRef]

10.

B. Munk, Frequency Selective Surfaces: Theory and Design (John Wiley & Sons, 2000).

11.

W. W. Salisbury, US Patent No. 2599944 (1952).

12.

P. B. Johnson and R. W. Christy, “Optical Constants of the Noble Metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]

13.

M. A. Ordal, L. L. Long, R. J. Bell, S. E. Bell, R. R. Bell, R. W. Alexander Jr, and C. A. Ward, “Optical-Properties of the Metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the Infrared and Far Infrared,” Appl. Opt. 22(7), 1099–1119 (1983). [CrossRef]

14.

H. Lochbihler, “Surface polaritons on gold-wire gratings,” Phys. Rev. B 50(7), 4795–4801 (1994). [CrossRef]

15.

C. P. Huang, S. B. Wang, X. G. Yin, Y. Zhang, H. Liu, Y. Y. Zhu, and C. T. Chan, “Enhanced electromagnetic pressure in a sandwiched reflection grating,” Phys. Rev. B 86(8), 085446 (2012). [CrossRef]

16.

C. P. Huang, X. G. Yin, Y. Zhang, S. B. Wang, Y. Y. Zhu, H. Liu, and C. T. Chan, “Deep subwavelength Fabry-Perot-like resonances in a sandwiched reflection grating,” Phys. Rev. B 85(23), 235410 (2012). [CrossRef]

17.

J. Zhou, L. Jin, and E. Y.-B. Pun, “Tunable multichannel nonreciprocal perfect absorber based on resonant absorption,” Opt. Lett. 37(13), 2613–2615 (2012). [CrossRef]

18.

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

OCIS Codes
(140.4780) Lasers and laser optics : Optical resonators
(240.0310) Optics at surfaces : Thin films
(310.1620) Thin films : Interference coatings

ToC Category:
Thin Films

History
Original Manuscript: July 9, 2013
Revised Manuscript: September 26, 2013
Manuscript Accepted: September 27, 2013
Published: October 16, 2013

Citation
Shiwei Shu, Zhe Li, and Yang Yang Li, "Triple-layer Fabry-Perot absorber with near-perfect absorption in visible and near-infrared regime," Opt. Express 21, 25307-25315 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-21-25307


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References

  1. N. I. Landy, S. Sajuyigbe, J. J. Mock, D. R. Smith, and W. J. Padilla, “Perfect Metamaterial Absorber,” Phys. Rev. Lett.100(20), 207402 (2008). [CrossRef]
  2. M. Diem, T. Koschny, and C. M. Soukoulis, “Wide-angle perfect absorber/thermal emitter in the terahertz regime,” Phys. Rev. B79(3), 033101 (2009). [CrossRef]
  3. J. J. Greffet, R. Carminati, K. Joulain, J. P. Mulet, S. P. Mainguy, and Y. Chen, “Coherent emission of light by thermal sources,” Nature416(6876), 61–64 (2002). [CrossRef]
  4. N. Liu, M. Mesch, T. Weiss, M. Hentschel, and H. Giessen, “Infrared Perfect Absorber and Its Application As Plasmonic Sensor,” Nano Lett.10(7), 2342–2348 (2010). [CrossRef]
  5. B. X. Zhang, Y. H. Zhao, Q. Z. Hao, B. Kiraly, I. C. Khoo, S. F. Chen, and T. J. Huang, “Polarization-independent dual-band infrared perfect absorber based on a metal-dielectric-metal elliptical nanodisk array,” Opt. Express19(16), 15221–15228 (2011). [CrossRef]
  6. C. G. Hu, Z. Y. Zhao, X. N. Chen, and X. G. Luo, “Realizing near-perfect absorption at visible frequencies,” Opt. Express17(13), 11039–11044 (2009). [CrossRef]
  7. J. M. Hao, J. Wang, X. L. Liu, W. J. Padilla, L. Zhou, and M. Qiu, “High performance optical absorber based on a plasmonic metamaterial,” Appl. Phys. Lett.96(25), 251104 (2010). [CrossRef]
  8. M. A. Kats, D. Sharma, J. Lin, P. Genevet, R. Blanchard, Z. Yang, M. M. Qazilbash, D. N. Basov, S. Ramanathan, and F. Capasso, “Ultra-thin perfect absorber employing a tunable phase change material,” Appl. Phys. Lett.101(22), 221101 (2012). [CrossRef]
  9. S. Shu and Y. Y. Li, “Metallic rugate structures for near-perfect absorbers in visible and near-infrared regions,” Opt. Lett.37(17), 3495–3497 (2012). [CrossRef]
  10. B. Munk, Frequency Selective Surfaces: Theory and Design (John Wiley & Sons, 2000).
  11. W. W. Salisbury, US Patent No. 2599944 (1952).
  12. P. B. Johnson and R. W. Christy, “Optical Constants of the Noble Metals,” Phys. Rev. B6(12), 4370–4379 (1972). [CrossRef]
  13. M. A. Ordal, L. L. Long, R. J. Bell, S. E. Bell, R. R. Bell, R. W. Alexander, and C. A. Ward, “Optical-Properties of the Metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the Infrared and Far Infrared,” Appl. Opt.22(7), 1099–1119 (1983). [CrossRef]
  14. H. Lochbihler, “Surface polaritons on gold-wire gratings,” Phys. Rev. B50(7), 4795–4801 (1994). [CrossRef]
  15. C. P. Huang, S. B. Wang, X. G. Yin, Y. Zhang, H. Liu, Y. Y. Zhu, and C. T. Chan, “Enhanced electromagnetic pressure in a sandwiched reflection grating,” Phys. Rev. B86(8), 085446 (2012). [CrossRef]
  16. C. P. Huang, X. G. Yin, Y. Zhang, S. B. Wang, Y. Y. Zhu, H. Liu, and C. T. Chan, “Deep subwavelength Fabry-Perot-like resonances in a sandwiched reflection grating,” Phys. Rev. B85(23), 235410 (2012). [CrossRef]
  17. J. Zhou, L. Jin, and E. Y.-B. Pun, “Tunable multichannel nonreciprocal perfect absorber based on resonant absorption,” Opt. Lett.37(13), 2613–2615 (2012). [CrossRef]
  18. E. D. Palik, Handbook of Optical Constants of Solids (Academic Press, 1985).

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