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- Publisher
- Hindawi Publishing Corporation
- Copyright
- Copyright © 2011 Yuu Wakabayashi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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- 1687-563X
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- 1687-5648
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- 10.1155/2011/867271
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Abstract
Hindawi Publishing Corporation Advances in OptoElectronics Volume 2011, Article ID 867271, 6 pages doi:10.1155/2011/867271 Research Article A TM-Pass/TE-Stop Polarizer Based on a Surface Plasmon Resonance Yuu Wakabayashi, Junji Yamauchi, and Hisamatsu Nakano Faculty of Engineering, Hosei University, 3-7-2 Kajino-cho, Koganei, Tokyo 184-8584, Japan Correspondence should be addressed to Yuu Wakabayashi, yuu.wakabayashi.27@gs-eng.hosei.ac.jp Received 15 June 2010; Accepted 16 July 2010 Academic Editor: Ana Vukovic Copyright © 2011 Yuu Wakabayashi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A TM-pass/TE-stop polarizer consisting of a metal film sandwiched between dielectric gratings is investigated using the finite- difference time-domain method. At normal incidence with respect to the grating plane, a transmissivity of more than 94% and a reflectivity of more than 98% are obtained at λ = 1.55 μm for the TM and TE waves, respectively. The extinction ratio is more than 17 dB over a wavelength range of 1.50 μmto1.75 μm. A high extinction ratio is maintained at oblique incidence, although the wavelength range shifts towards longer wavelengths. The TM-pass/TE-stop operation is also achieved with a modified structure, in which a dielectric grating is sandwiched between metal films. 1. Introduction range, in which the high ER is observed, shifts towards longer wavelengths. There are a great number of papers devoted to the study To alleviate the fabrication difficulty, we also deal of light propagation in periodic structures [1]. One of with a modified structure, in which a dielectric grating the important applications of the periodic structures is to is sandwiched between metal films. The TM-pass/TE-stop construct a polarizer, which is used in optical communica- operation is achieved at λ = 1.55 μm, although the transmis- tions and sensing devices. Recently, high transmission of the sivity is low compared with that obtained from the original transverse magnetic (TM) wave through a thin metal film structure. has been suggested and discussed [2–4]. The transmission is closely related to a surface plasmon (SP) resonance [5]. The SP resonance is realized using a thin metal film sandwiched 2. Configuration and Numerical Method between dielectric gratings. We should also note that recent Figure 1 illustrates the periodic structure of the polarizer, in interest has been directed toward plasmon waveguides which a two-dimensional model is treated. The configuration operating at λ 1.55 μm (optical communication band) is similar to that treated in [2, 3]. We illuminate a uniform [6, 7]. plane wave of either the TE or the TM wave from the input In this paper, the SP-based enhanced transmission side and intend to extract the TE wave as a reflected field at through a thin metal film is investigated in more detail in the input side and the TM wave as a transmission field at the optical communication band. The finite-difference time- the output side. Note that from a different aspect, a similar domain (FDTD) method is used for the analysis. To obtain structure was also investigated as a low-loss surface plasmon a high transmissivity for the TM wave and a high reflectivity Bragg grating [8]. for the transverse electric (TE) wave with a subsequent high extinction ratio (ER), we appropriately choose the width and The refractive indices of the dielectric materials are taken thickness of the dielectric grating. In addition to normal to be n = 3.715 and n = 2.049. The width and thickness of H L incidence with respect to the grating plane, we consider the the dielectric grating are designated as w and t ,respectively. case of oblique incidence. It was found that the wavelength The widths of the low- and high-index dielectric regions 2 Advances in OptoElectronics 0.45 25 Air 0.4 0.35 12.5 0.3 t w w d n n H L n 0.25 0 0.2 Air 0.15 −12.5 Figure 1: Configuration. 0.1 0.05 −25 0.45 1 0.10.2 0.30.4 Width of dielectric grating, w (μm) 0.4 0.88 Figure 3: Extinction ratio observed at the output (λ = 1.55 μm). 0.35 0.75 0.3 0.63 for w = 0.29 μmand t = 0.22 μm. We, therefore, adopt these 0.25 0.5 d configuration parameters in the following discussion. 0.2 0.38 The determined periodicity is consistent with the follow- ing relationship at normal incidence, that is, θ = 0 : 0.15 0.25 2π 0.1 0.13 k = k sin θ ± , (2) sp 0 0.05 0 where k is the free-space wavenumber; Λ(=2w) is the 0.10.2 0.30.4 periodicity; k is the propagation constant of the SP mode, sp Width of dielectric grating, w (μm) which can be obtained by the eigenmode analysis. Note that Figure 2: Transmissivity of TM wave (λ = 1.55 μm). in the eigenmode analysis the refractive index of the dielectric grating is approximately modeled as a homogeneous layer (2) with second-order effective index for the TM wave (n ), TM which is calculated by the effective medium theory [1]: are set to be the same, that is, w = w . The Drude model is used to express the dispersion of a metal. The refractive 1/2 index and thickness of the metal (Ag) film are chosen to be 1 Λ 2 (2) 2 −2 −2 6 2 n = n + π f 1 − f n − n n n , TM TM H L TM TE n = 0.144 − j 11.214 at λ = 1.55 μm[9]and t = 0.03 μm. 3 λ m m To analyze the present polarizer, we adopt the FDTD (3) method together with the periodic boundary condition, to where λ is the free-space wavelength, and f is the grating fill which the field transformation technique [10] is applied. 0 factor. n and n are the first-order effective indices for the The piecewise linear recursive convolution technique [11]is TE TM TE and TM waves, which are, respectively, expressed as employed so as to treat the structure involving the metal film. The numerical parameters are chosen to be Δx = Δz = 5nm. 1/2 2 2 2 n = n + f n − n , We consider the case where a linearly polarized plane wave is TE L H L (4) incident towards the +z direction whose angle of incidence is −1/2 −2 −2 −2 n = n + f n − n . defined by θ. TM L H L To obtain a high transmissivity for the TM wave with a subsequent high ER, we determine the configuration param- 3. Wavelength Characteristics eters of dielectric gratings. Figures 2 and 3, respectively, show the transmissivity for the TM wave and the ER at λ = 1.55 μm Figure 4 shows the reflectivity and transmissivity at normal as a joint function of w and t . The angle of incidence is incidence as a function of wavelength. For the TE wave, the typically fixed to be θ = 0 .The ER is defined by reflectivity is close to unity over a wide range of wavelengths. The maximum transmissivity for the TM wave is calculated T to be 94% at λ = 1.55 μm. The ratio of the transmitted TM ER = 10 log , (1) T field to the reflected field is less than −30 dB. This means TE that the nontransmitted power is almost absorbed in the where T and T are the transmissivities for the TM and metal film. It should be noted that the double-humped TM TE TE waves, respectively. Calculation shows that the transmis- behavior is observed in the transmissivity. This behavior is sivity reaches a maximum value of 94% with an ER of 20 dB caused by the fact that the structure supports asymmetric Thickness of dielectric grating, t (μm) Transmissivity Thickness of dielectric grating, t (μm) Extinction ratio (dB) Advances in OptoElectronics 3 1.6 10 TE wave 1.4 7.5 0.8 0.6 1.2 TM wave 0.4 2.5 0.2 0.8 −0.2 −0.10 0.10.2 1.41.5 1.61.71.8 x (μm) Wavelength (μm) TE wave (a) Transmissivity Reflectivity 1.6 10 Figure 4: Wavelength characteristics at normal incidence (θ = 0 ). 1.4 7.5 and symmetric modes, which, respectively, correspond to the first and second SP modes [12]. Figures 5(a) and 5(b) show the H -field distributions observed at λ = 1.69 μm 1.2 and 1.55 μm, respectively. Only the fields observed in single cells are presented due to the periodicity. The high-index region is situated from x =−0.145 μmto x = 0.145 μm. The 2.5 field in Figure 5(a) exhibits the asymmetric distribution with respect to the middle plane of the metal film, while that in Figure 5(b) exhibits the symmetric distribution. The ERs observed at the input and output sides are 0.8 0 −0.2 −0.10 0.10.2 presented in Figure 6. The present polarizer maintains a high x (μm) ER of more than 17 dB for the TM wave (at the output) over a wavelength range of 1.50 μmto1.75 μm. The maximum (b) ER is calculated to be approximately 20 dB at λ = 1.55 μm. Figure 5: Field distributions at (a) λ = 1.69 μm and (b) λ = The ER for the TE wave (at the input) is more than 30 dB at 1.55 μm. λ = 1.55 μm. We next study the case of oblique incidence, where θ is typically set to be 20 . Figures 7 and 8, respectively, show the transmissivity and the ER each as a function of wavelength. Therefore, the wavelength at which the SP mode is excited For reference, the data at normal incidence shown in Figures at normal incidence is separated into two wavelengths. In 4 and 6 are again plotted. The maximum transmissivity Figure 7, the first two modes are excited at λ = 1.53 μm sp is obtained at λ = 1.62 μm, and then the triple-humped and λ = 1.79 μm, which are separated from λ = 1.69 μm sp sp ◦ − behavior is observed in this wavelength range. Figure 8 also for θ = 0 . Only the second mode determined by k can be sp − + shows that the region where the high ER is maintained shifts seen at λ = 1.63 μm because the other one (λ = 1.33 μm) sp sp towards longer wavelengths. This behavior can be explained is beyond the scale. As a result, the triple-humped behavior in terms of (2). At normal incidence, only the SP mode of the transmissivity at oblique incidence is observed in this whose propagation constant is determined by ±2π/Λ is wavelength range. excited, propagating in opposite directions along the metal- dielectric interface. However, when the angle of incidence is 4. Modified Structure varied from θ = 0 , this symmetry is broken. In other words, (2) provides the following two relationships: In the preceding section, we have studied the characteristics of the polarizer consisting of the metal film sandwiched 2π k = k sin θ + , between dielectric gratings. This polarizer requires that the sp structure be symmetric with respect to the metal film to (5) 2π excite the SP mode. It is, however, not easy to fabricate the k = k sin θ − . sp Λ symmetrical structure at a lightwave frequency, since a set of Reflectivity, transmissivity z (μm) z (μm) 4 Advances in OptoElectronics 30 25 0 0 1.41.5 1.61.71.81.9 1.41.5 1.61.71.81.9 Wavelength (μm) Wavelength (μm) Output 0 Input 20 Figure 8: Extinction ratio as a function of wavelength. Figure 6: Extinction ratio at normal incidence (θ = 0 ). 0.8 Air 0.6 0.4 TM wave t w d w n n H n m 0.2 L Air 1.41.5 1.61.71.8 Figure 9: Configuration of a modified structure. Wavelength (μm) TE wave Figure 7: Transmissivity as a function of wavelength. dielectric gratings must be placed precisely. In this section, 0.8 we, therefore, investigate a more practical configuration. We propose the configuration shown in Figure 9,in 0.6 which a single dielectric grating is sandwiched between metal TE wave films. The refractive indices are the same as those treated in the previous section. It should be noted that the absorption TM wave 0.4 loss is closely related to the thickness of the metal film. Since there exist the two metal films in the modified structure, 0.2 we have decreased the metal thickness to sufficiently reduce the loss, so that t is taken to be 0.01 μm. To achieve the TM-pass/TE-stop operation at λ = 1.55 μm, we have carried out some preliminary calculations similar to those shown 1.41.5 1.61.7 in Figure 2 and finally chose t = 0.44 μmand w = w = Wavelength (μm) 0.25 μm. Transmissivity Figures 10 and 11 show the data corresponding to those Reflectivity shown in Figures 4 and 6, respectively. It was found that a transmissivity of more than 76% for the TM wave and a Figure 10: Wavelength characteristics. Transmissivity Extinction ratio (dB) Reflectivity, transmissivity Extinction ratio (dB) Advances in OptoElectronics 5 more than 94% for the TM wave is obtained at λ = 1.55 μm. A high ER of more than 17 dB is observed over a wavelength range of 1.50 μmto1.75 μm. The high ER region is also 15 maintained at oblique incidence, although the wavelength range shifts towards longer wavelengths. Further consideration has been devoted to a more practical model in which a dielectric grating is sandwiched between metal films. The TM-pass/TE-stop operation is achieved at λ = 1.55 μm with a transmissivity of more than 76%. The ER at the output side is calculated to be 12 dB. Acknowledgments The authors would like to thank Mr. Koji Sumida for his basic 1.41.5 1.61.7 investigations of the present work. This paper was supported Wavelength (μm) in part by MEXT, Grant-in-Aid for Scientific Research (c) Output (22560350). Input Figure 11: Extinction ratio as a function of wavelength. References [1] R. Magnusson and D. Shin, “Diffractive optical components,” in Encyclopedia of Physical Science and Technology, vol. 4, pp. 421–440, Academic Press, New York, NY, USA, 3rd edition, [2] V. M. Fitio and Y. V. Bobitski, “High transmission of system “dielectric grating thin metal film—dielectric grating”,” in Proceedings of the 7th International Conference on Laser and 0.8 Fiber-Optical Networks Modeling (LFNM ’05), pp. 163–166, 8 September 2005. [3] J. Yamauchi, K. Sumida, and H. Nakano, “A TMpass/ TE-stop 0.6 polarizer consisting of a metal film sandwiched with dielectric gratings,” in Proceedings of the 10th International Symposium on Contemporary Photonics Technology, vol. G-15, pp. 93–94, Tokyo, Japan, 2007. 0.4 [4] J. Yamauchi, T. Yamazaki, K. Sumida, and H. Nakano, “TM/TE wave splitters using surface plasmon polaritons,” in Integrated −0.2 −0.10 0.10.2 Photonics and Nanophotonics Research and Applications,Salt Lake City, Utah, USA, July 2007. x (μm) [5] J. M. Steele, C. E. Moran, A. Lee, C. M. Aguirre, and N. J. Figure 12: Field distribution (λ = 1.55 μm). Halas, “Metallodielectric gratings with subwavelength slots: optical properties,” Physical Review B, vol. 68, no. 20, Article ID 205103, 7 pages, 2003. [6] T. Nikolajsen, K. Leosson, and S. I. Bozhevolnyi, “Surface reflectivity of more than 94% for the TE wave are obtained plasmon polariton based modulators and switches operating at λ = 1.55 μm, although the transmissivity is low compared at telecom wavelengths,” Applied Physics Letters, vol. 85, no. with that obtained from the original structure discussed 24, pp. 5833–5835, 2004. in Section 3. In contrast with the original structure, the [7] K.-Y. Jung,F.L.Teixeira, andR.M.Reano, “Au/SiO nanoring enhanced transmission can be explained in terms of the plasmon waveguides at optical communication band,” Journal of Lightwave Technology, vol. 25, no. 9, pp. 2757–2765, 2007. Fabry-Per ´ ot-like resonance in the cavity between the metal films [13]. The field distribution observed at λ = 1.55 μm [8] J.-W. Mu and W.-P. Huang, “A low-loss surface plasmonic Bragg grating,” Journal of Lightwave Technology, vol. 27, no. is illustrated in Figure 12, which clearly indicates a standing 4, pp. 436–439, 2009. wave behavior in the high-index region. The ERs at the [9] P.B.Johnson andR.W.Christy,“Opticalconstants of the output and input sides are calculated to be 12 dB and 18 dB noble metals,” Physical Review B, vol. 6, no. 12, pp. 4370–4379, at λ = 1.55 μm, respectively. [10] A. Taflove and S. Hagness, Computational Electrodynamics: 5. Conclusion The Finite-Difference Time-Domain Method,ArtechHouse, Norwood, Mass, USA, 2000. A TM-pass/TE-stop polarizer using the surface plasmon [11] D. F. Kelley and R. I. Luebbers, “Piecewise linear recursive con- resonance has been analyzed by the FDTD method. At volution for dispersive media using FDTD,” IEEE Transactions normal incidence, calculation shows that a transmissivity of on Antennas and Propagation, vol. 44, no. 6, pp. 792–797, 1996. Extinction ratio (dB) z (μm) 6 Advances in OptoElectronics [12] P. Berini, “Plasmon-polariton waves guided by thin lossy metal films of finite width: bound modes of symmetric structures,” Physical Review B, vol. 61, no. 15, pp. 10484–10503, 2000. [13] E. Popov, S. Enoch, G. Tayeb, M. Nevier ` e, B. Gralak, and N. Bonod, “Enhanced transmission due to nonplasmon resonances in one- and two-dimensional gratings,” Applied Optics, vol. 43, no. 5, pp. 999–1008, 2004. 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Published: Aug 22, 2010