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High tunable optical properties of monolayer corrugated hetero-colloidal crystals
Materials Letters 116 (2014) 382–385
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
High tunable optical properties of monolayer corrugated hetero-colloidal crystals Z.Q. Liu a, G.Q. Liu a,n, J. Chen b, Y. Hu a, X.N. Zhang a, Z.J. Zheng a a b
Laboratory of Nanomaterials and Sensors, College of Physics and Communication Electronics, Jiangxi Normal University, Nanchang 330022, China College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
art ic l e i nf o
a b s t r a c t
Article history: Received 14 September 2013 Accepted 21 November 2013 Available online 28 November 2013
We design and fabricate a novel quasi-three dimensional corrugated hetero-colloidal crystal. Both measured and calculated results show a high tunable optical transmission response of the proposed structure via changing the geometry parameters of the coated dielectric film. Two different dielectric materials with low and relative higher refractive index are used as the coated films and different optical responses are achieved. Dual largely deepened transmission dips with a much bigger frequency shift are observed in the structure with a dielectric film consisting of higher dielectric constant materials. Our findings could provide potential applications in light harvesting and optical circuits. & 2013 Elsevier B.V. All rights reserved.
Keywords: Optical materials and properties Metallic composites Microstructure
1. Introduction Colloidal crystals (CCs) display many properties analogous to semiconductors, including the appearance of pass bands and band gaps [1–3]. Large-area monolayer CCs could be fabricated by the well-developed self-assembly or spin-coating methods [4,5]. Numerous applications based on the two dimensional (2D) CCs have been explored and developed since it emerged [3,6,7]. However, most efforts were focused on the applications by using the 2D CCs as the precursor templates. For instance, 2D CCs have been employed as masks or templates for evaporation, deposition, etching, and imprinting, etc [8–11]. Light harvesting, flow modulation, and significant enhancement in the sunlight absorption have been presented by the exploration of photonic guided modes (GMs) supported by the monolayer CCs or the colloids [12–14]. Recently, CC heterostructures [3] have been introduced to extend many attractive features of their semiconductor counterparts into the optical domain. Compared with the single CCs, heterostructures can generate many complex functions in compact components such as waveguides and resonant cavities [3,15]. However, almost all the reports were based on the modulations on the light propagation or scattering by three-dimensional (3D) CCs or 2D planar CCs [14–20]. Far less attention has been focused on the heterostructure-like crystal based on the 2D CC. In this work, we fabricate monolayer hetero-colloidal crystals (HCCs) based on the 2D CCs via the physical vapor deposition of silica (SiO2, ε ¼2.13) or titanium oxide (TiO2, ε ¼6.25) dielectric
n
Corresponding author. Tel./fax: þ 86 79 18 120370. E-mail addresses: [email protected], [email protected] (G.Q. Liu).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.11.087
material onto the CC substrates to form the semi-shell corrugated film. Both the experimental and simulation results present strong optical modulations in both intensity and frequency. For the HCC with a TiO2 film, strongly enhanced light coupling and confinement effects are achieved, accompanied by much deeper transmission dips in the transmission spectra. Our findings could provide potential applications for the light flow modulation and light energy harvesting. 2. Experimental details Monodisperse polystyrene (PS) spheres with 980 nm in diameter (polydispersity o3%, refractive index n ¼1.59) were purchased from Duke Sci. Cor. PS spheres were firstly oscillated and diluted to 1 wt% by de-ionized water and then self-assembled on a cleaned quartz substrate to form a 2D CC. Following this, a dielectric film (SiO2 or TiO2) with certain thickness was deposited on top of the CC via the physical vapor deposition to form the HCC. Schematic diagrams of the 2D CC and HCC are shown in Fig. 1 (a) and (b), respectively. The transmission spectra were measured using a commercial UV–vis–IR spectrometer under normal incident light irradiation. The sample structures were characterized by the scanning electron microscopy (SEM, S-3400 N). Simulation calculations were performed with the 3D finite-difference time-domain method [21]. Each PS sphere is assumed to be half-coated by the dielectric film as shown in Fig. 1b. Periodic boundary conditions for the unit cell are adopted and the computational domain is terminated by perfect matching layers. The illumination light is along the z axis with its electric polarization along the x axis.
Z.Q. Liu et al. / Materials Letters 116 (2014) 382–385
383
Fig. 1. Schematic diagrams of (a) 2D CC and (b) HCC. (c) Optical photo of the fabricated CC and SEM images of (d) CC and (e) HCC. Inset: diffraction pattern.
Fig. 2. (a) Measured transmission spectra with an offset by 10% from each other of HCCs with different SiO2 film height. (b) Position shifts of transmission dips at the long and short wavelength ranges as a function of h.
3. Results and discussion A high-quality 2D CC consisting of PS spheres is self-assembled as the optical photo and SEM image shown in Fig. 1c and d. The clear diffractive pattern with different orders obtained with a 633 nm laser irradiation normal to the sample also confirms the high-quality of the sample (see the inset). After a dielectric film is then deposited on this CC, a HCC is formed as shown in Fig. 1e. The semi-shell corrugated coating film is clearly observed here. The height (h) of the dielectric film is defined as the distance between the top of the dielectric film and the top of the sphere along z axis. Fig. 2a shows the measured transmission spectra of the HCC by varying the thickness of the SiO2 film coated on the 2D CC. The transmission spectrum of the conventional 2D CC (h¼0 nm) presents a main dip (at long wavelength range for the low-order GM) at λ ¼1270 nm and a sub-dip (at short wavelength range for the high-order GM) at λ ¼1055 nm. With increasing h, obvious amplitude modifications on the transmission dips are obtained. The dip at short wavelength range becomes more obvious while for the dip at long wavelength range becomes weak. Moreover, by profiling the positions of transmission minimum in GM bands as a function of h, the red-shift of the dip at short wavelength range is three-times larger than that at long wavelength range (Fig. 2b). These features might result from the light coupling and confinement efficiencies for different photonic GMs [7,22]. Fig. 3 shows the calculated transmission spectra and corresponding electric field intensity distributions of the structures. The calculated spectra agree well with the measured ones. As shown in
Fig. 3a, a main dip at λ ¼1212 nm and a sub-dip at λ ¼1008 nm is obtained for the conventional CC. With h ¼450 nm, dual transmission dips at λ ¼1236 nm and 1070 nm are observed, accompanied by the reduced depths and obvious red-shifts. For the CC, the electric field intensity distributions at λ¼ 1212 nm (Fig. 3b) and at λ¼ 1008 nm (Fig. 3c) respectively present the confined and leaky photonic GMs. With h ¼450 nm, at λ ¼1236 nm the main electric field intensity is still confined in the PS sphere and without obvious energy leaky into the silica film (Fig. 3d), again confirming that the GM here is a cavity mode. At λ ¼1070 nm the main electric field intensity is observed in the silica film (Fig. 3e), indicating the excitation of leaky GM. We further study the optical properties of the HCCs by replacing SiO2 with TiO2 as the deposition film. Measured transmission spectra of the HCCs with different h are shown in Fig. 4a. With h increasing, stronger and stronger double transmission dips with continuous red-shifts (Fig. 4b) are observed, quite different from those of the HCCs with a SiO2 film in Fig. 2b, suggesting different optical responses of the structure due to high dielectric constant materials used. Fig. 4c shows the calculated transmission spectra of HCCs with different TiO2 film height. With h¼150 nm, two strong transmission dips at λ¼1368 nm and 1140 nm are observed, in good agreement with the measured ones. Main electric field intensity distributions as shown in Fig. 4d are concentrated at the interface between the TiO2 film and the PS sphere, indicating strong optical field coupling and confinement effects and confirming the red-shift of the dip at λ ¼1368 nm due to the main electric filed distributed in the higher dielectric constant film. It should be
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Z.Q. Liu et al. / Materials Letters 116 (2014) 382–385
Fig. 3. (a) Calculated transmission spectra of HCCs with different SiO2 film height. (b) and (c) Electric field intensity distributions for the conventional CC at λ ¼ 1212 nm and 1008 nm, respectively. (d) and (e) Electric field intensity distributions for the HCC with h ¼ 450 nm at λ ¼ 1236 nm and 1070 nm, respectively. The black dashed circle marks the sphere.
Fig. 4. (a) Measured transmission spectra with the offset by 10% from each other of HCCs with different TiO2 film height. (b) Position shifts of the transmission dips at the long and short wavelength ranges as a function of h. (c) Calculated transmission spectra of HCCs with different TiO2 film height. (d) and (e) Electric field intensity distributions for the HCC with h ¼150 nm at λ ¼1368 nm and 1140 nm, respectively. The black dashed circle marks the sphere.
noted that the high dielectric constant film coated on the sphere could even change the original confinement of the low order GM to be a hybrid-like photonic mode distributed in both the coating film and the sphere. For the dip at λ¼ 1140 nm, the main electric field intensity distributions are in the sphere and at the outer surface of the TiO2 film (Fig. 4d), suggesting the strong coupling of optical field by the high dielectric constant material.
4. Conclusions We have fabricated novel monolayer HCCs and demonstrated the high tunable optical transmission response by using different dielectric materials. As for the structure with a low refractive index dielectric film, the transmission spectra show shallowing transmission dips with different frequency shift evolutions. As for the structure with a high dielectric constant film, double largely deepened transmission dips with similar frequency shift
evolutions are achieved. In addition, the photonic GMs in the CC could be highly modulated by the outer coated dielectric film. These may provide potential applications in the sub-wavelength nano-optics, light absorption, and photonic circuits.
Acknowledgments Work was funded by the National Natural Science Foundation of China (Nos.11004088, 11264017, 11304059), Natural Science Foundation of Jiangxi Province (No. 20122BAB202006), Scientific and Technological Supporting Projects of Jiangxi Province (No.20112BBE50033). References [1] Guo W, Wang M, Xia W, Dai L. J Mater Res 2012;27:1663–71. [2] Zhang Y, Fu M, Wang J, He D, Wang Y. Opt Mater 2012;34:1758–61.
Z.Q. Liu et al. / Materials Letters 116 (2014) 382–385
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Istrate E, Sargent EH. Rev Mod Phys 2006;78:455–81. Freymann G, Kitaev V, Lotsch BV, Ozin GA. Chem Soc Rev 2013;42:2528–54. Jiang P, Prasad T, McFarland MJ, Colvin VL. Appl Phys Lett 2006;89:011908. Ding B, Hrelescu C, Arnold N, Isic G, Klar TA. Nano Lett 2013;13:3786. Romanov SG, Korovin AV, Regensburger A, Peschel U. Adv Mater 2011;23:2515–33. Hall AS, Friesen SA, Mallouk TE. Nano Lett 2013;13:2623–7. Zhang J, Li Y, Zhang X, Yang B. Adv Mater 2010;22:4249–69. Ye X, Qi L. Nano Today 2011;6:608–31. Yang S, Lei Y. Nanoscale 2011;3:2768–82. Mitsui T, Wakayama Y, Onodera T, Hayashi T, Ikeda N, Sugimoto Y. Adv Mater 2010;22:3022–6. Kang G, Park H, Shin D, Baek S, Choi M, Yu D. Adv Mater 2013;25:2617–23.
385
[14] Ding B, Bardosova M, Povey I, Pemble ME, Romanov SG. Adv Funct Mater 2010;20:853–60. [15] Takahashi Y, Inui Y, Chihara M, Asano T, Terawaki R, Noda S. Nature 2013;498:470–4. [16] Liu GQ, Li L, Gong LX, Tang FL, Wang Q. Mater Lett 2012;68:466–8. [17] Liu GQ, Liu ZQ, Huang K, Chen YH, Li L, Tang FL, et al. Mater Lett 2013;93:42–4. [18] Liu ZQ, Feng TH, Dai QF, Wu LJ, Lan S. Chin Phys B 2009;18:2383–8. [19] Istrate E, Sargent EH. J Opt A 2002;4:S242. [20] Tomljenovic-Hanic S, Martijn de Sterke C, Steel MJ. Opt Express 2006;14:12451–6. [21] Liu ZQ, Liu GQ, Zhou H, Liu X, Huang K, Chen Y. Nanotechnology 2013;24:155203. [22] Farcau C, Astilean S. J Opt A 2007;9:S345–9.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
High tunable optical properties of monolayer corrugated hetero-colloidal crystals Z.Q. Liu a, G.Q. Liu a,n, J. Chen b, Y. Hu a, X.N. Zhang a, Z.J. Zheng a a b
Laboratory of Nanomaterials and Sensors, College of Physics and Communication Electronics, Jiangxi Normal University, Nanchang 330022, China College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
art ic l e i nf o
a b s t r a c t
Article history: Received 14 September 2013 Accepted 21 November 2013 Available online 28 November 2013
We design and fabricate a novel quasi-three dimensional corrugated hetero-colloidal crystal. Both measured and calculated results show a high tunable optical transmission response of the proposed structure via changing the geometry parameters of the coated dielectric film. Two different dielectric materials with low and relative higher refractive index are used as the coated films and different optical responses are achieved. Dual largely deepened transmission dips with a much bigger frequency shift are observed in the structure with a dielectric film consisting of higher dielectric constant materials. Our findings could provide potential applications in light harvesting and optical circuits. & 2013 Elsevier B.V. All rights reserved.
Keywords: Optical materials and properties Metallic composites Microstructure
1. Introduction Colloidal crystals (CCs) display many properties analogous to semiconductors, including the appearance of pass bands and band gaps [1–3]. Large-area monolayer CCs could be fabricated by the well-developed self-assembly or spin-coating methods [4,5]. Numerous applications based on the two dimensional (2D) CCs have been explored and developed since it emerged [3,6,7]. However, most efforts were focused on the applications by using the 2D CCs as the precursor templates. For instance, 2D CCs have been employed as masks or templates for evaporation, deposition, etching, and imprinting, etc [8–11]. Light harvesting, flow modulation, and significant enhancement in the sunlight absorption have been presented by the exploration of photonic guided modes (GMs) supported by the monolayer CCs or the colloids [12–14]. Recently, CC heterostructures [3] have been introduced to extend many attractive features of their semiconductor counterparts into the optical domain. Compared with the single CCs, heterostructures can generate many complex functions in compact components such as waveguides and resonant cavities [3,15]. However, almost all the reports were based on the modulations on the light propagation or scattering by three-dimensional (3D) CCs or 2D planar CCs [14–20]. Far less attention has been focused on the heterostructure-like crystal based on the 2D CC. In this work, we fabricate monolayer hetero-colloidal crystals (HCCs) based on the 2D CCs via the physical vapor deposition of silica (SiO2, ε ¼2.13) or titanium oxide (TiO2, ε ¼6.25) dielectric
n
Corresponding author. Tel./fax: þ 86 79 18 120370. E-mail addresses: [email protected], [email protected] (G.Q. Liu).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.11.087
material onto the CC substrates to form the semi-shell corrugated film. Both the experimental and simulation results present strong optical modulations in both intensity and frequency. For the HCC with a TiO2 film, strongly enhanced light coupling and confinement effects are achieved, accompanied by much deeper transmission dips in the transmission spectra. Our findings could provide potential applications for the light flow modulation and light energy harvesting. 2. Experimental details Monodisperse polystyrene (PS) spheres with 980 nm in diameter (polydispersity o3%, refractive index n ¼1.59) were purchased from Duke Sci. Cor. PS spheres were firstly oscillated and diluted to 1 wt% by de-ionized water and then self-assembled on a cleaned quartz substrate to form a 2D CC. Following this, a dielectric film (SiO2 or TiO2) with certain thickness was deposited on top of the CC via the physical vapor deposition to form the HCC. Schematic diagrams of the 2D CC and HCC are shown in Fig. 1 (a) and (b), respectively. The transmission spectra were measured using a commercial UV–vis–IR spectrometer under normal incident light irradiation. The sample structures were characterized by the scanning electron microscopy (SEM, S-3400 N). Simulation calculations were performed with the 3D finite-difference time-domain method [21]. Each PS sphere is assumed to be half-coated by the dielectric film as shown in Fig. 1b. Periodic boundary conditions for the unit cell are adopted and the computational domain is terminated by perfect matching layers. The illumination light is along the z axis with its electric polarization along the x axis.
Z.Q. Liu et al. / Materials Letters 116 (2014) 382–385
383
Fig. 1. Schematic diagrams of (a) 2D CC and (b) HCC. (c) Optical photo of the fabricated CC and SEM images of (d) CC and (e) HCC. Inset: diffraction pattern.
Fig. 2. (a) Measured transmission spectra with an offset by 10% from each other of HCCs with different SiO2 film height. (b) Position shifts of transmission dips at the long and short wavelength ranges as a function of h.
3. Results and discussion A high-quality 2D CC consisting of PS spheres is self-assembled as the optical photo and SEM image shown in Fig. 1c and d. The clear diffractive pattern with different orders obtained with a 633 nm laser irradiation normal to the sample also confirms the high-quality of the sample (see the inset). After a dielectric film is then deposited on this CC, a HCC is formed as shown in Fig. 1e. The semi-shell corrugated coating film is clearly observed here. The height (h) of the dielectric film is defined as the distance between the top of the dielectric film and the top of the sphere along z axis. Fig. 2a shows the measured transmission spectra of the HCC by varying the thickness of the SiO2 film coated on the 2D CC. The transmission spectrum of the conventional 2D CC (h¼0 nm) presents a main dip (at long wavelength range for the low-order GM) at λ ¼1270 nm and a sub-dip (at short wavelength range for the high-order GM) at λ ¼1055 nm. With increasing h, obvious amplitude modifications on the transmission dips are obtained. The dip at short wavelength range becomes more obvious while for the dip at long wavelength range becomes weak. Moreover, by profiling the positions of transmission minimum in GM bands as a function of h, the red-shift of the dip at short wavelength range is three-times larger than that at long wavelength range (Fig. 2b). These features might result from the light coupling and confinement efficiencies for different photonic GMs [7,22]. Fig. 3 shows the calculated transmission spectra and corresponding electric field intensity distributions of the structures. The calculated spectra agree well with the measured ones. As shown in
Fig. 3a, a main dip at λ ¼1212 nm and a sub-dip at λ ¼1008 nm is obtained for the conventional CC. With h ¼450 nm, dual transmission dips at λ ¼1236 nm and 1070 nm are observed, accompanied by the reduced depths and obvious red-shifts. For the CC, the electric field intensity distributions at λ¼ 1212 nm (Fig. 3b) and at λ¼ 1008 nm (Fig. 3c) respectively present the confined and leaky photonic GMs. With h ¼450 nm, at λ ¼1236 nm the main electric field intensity is still confined in the PS sphere and without obvious energy leaky into the silica film (Fig. 3d), again confirming that the GM here is a cavity mode. At λ ¼1070 nm the main electric field intensity is observed in the silica film (Fig. 3e), indicating the excitation of leaky GM. We further study the optical properties of the HCCs by replacing SiO2 with TiO2 as the deposition film. Measured transmission spectra of the HCCs with different h are shown in Fig. 4a. With h increasing, stronger and stronger double transmission dips with continuous red-shifts (Fig. 4b) are observed, quite different from those of the HCCs with a SiO2 film in Fig. 2b, suggesting different optical responses of the structure due to high dielectric constant materials used. Fig. 4c shows the calculated transmission spectra of HCCs with different TiO2 film height. With h¼150 nm, two strong transmission dips at λ¼1368 nm and 1140 nm are observed, in good agreement with the measured ones. Main electric field intensity distributions as shown in Fig. 4d are concentrated at the interface between the TiO2 film and the PS sphere, indicating strong optical field coupling and confinement effects and confirming the red-shift of the dip at λ ¼1368 nm due to the main electric filed distributed in the higher dielectric constant film. It should be
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Z.Q. Liu et al. / Materials Letters 116 (2014) 382–385
Fig. 3. (a) Calculated transmission spectra of HCCs with different SiO2 film height. (b) and (c) Electric field intensity distributions for the conventional CC at λ ¼ 1212 nm and 1008 nm, respectively. (d) and (e) Electric field intensity distributions for the HCC with h ¼ 450 nm at λ ¼ 1236 nm and 1070 nm, respectively. The black dashed circle marks the sphere.
Fig. 4. (a) Measured transmission spectra with the offset by 10% from each other of HCCs with different TiO2 film height. (b) Position shifts of the transmission dips at the long and short wavelength ranges as a function of h. (c) Calculated transmission spectra of HCCs with different TiO2 film height. (d) and (e) Electric field intensity distributions for the HCC with h ¼150 nm at λ ¼1368 nm and 1140 nm, respectively. The black dashed circle marks the sphere.
noted that the high dielectric constant film coated on the sphere could even change the original confinement of the low order GM to be a hybrid-like photonic mode distributed in both the coating film and the sphere. For the dip at λ¼ 1140 nm, the main electric field intensity distributions are in the sphere and at the outer surface of the TiO2 film (Fig. 4d), suggesting the strong coupling of optical field by the high dielectric constant material.
4. Conclusions We have fabricated novel monolayer HCCs and demonstrated the high tunable optical transmission response by using different dielectric materials. As for the structure with a low refractive index dielectric film, the transmission spectra show shallowing transmission dips with different frequency shift evolutions. As for the structure with a high dielectric constant film, double largely deepened transmission dips with similar frequency shift
evolutions are achieved. In addition, the photonic GMs in the CC could be highly modulated by the outer coated dielectric film. These may provide potential applications in the sub-wavelength nano-optics, light absorption, and photonic circuits.
Acknowledgments Work was funded by the National Natural Science Foundation of China (Nos.11004088, 11264017, 11304059), Natural Science Foundation of Jiangxi Province (No. 20122BAB202006), Scientific and Technological Supporting Projects of Jiangxi Province (No.20112BBE50033). References [1] Guo W, Wang M, Xia W, Dai L. J Mater Res 2012;27:1663–71. [2] Zhang Y, Fu M, Wang J, He D, Wang Y. Opt Mater 2012;34:1758–61.
Z.Q. Liu et al. / Materials Letters 116 (2014) 382–385
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Istrate E, Sargent EH. Rev Mod Phys 2006;78:455–81. Freymann G, Kitaev V, Lotsch BV, Ozin GA. Chem Soc Rev 2013;42:2528–54. Jiang P, Prasad T, McFarland MJ, Colvin VL. Appl Phys Lett 2006;89:011908. Ding B, Hrelescu C, Arnold N, Isic G, Klar TA. Nano Lett 2013;13:3786. Romanov SG, Korovin AV, Regensburger A, Peschel U. Adv Mater 2011;23:2515–33. Hall AS, Friesen SA, Mallouk TE. Nano Lett 2013;13:2623–7. Zhang J, Li Y, Zhang X, Yang B. Adv Mater 2010;22:4249–69. Ye X, Qi L. Nano Today 2011;6:608–31. Yang S, Lei Y. Nanoscale 2011;3:2768–82. Mitsui T, Wakayama Y, Onodera T, Hayashi T, Ikeda N, Sugimoto Y. Adv Mater 2010;22:3022–6. Kang G, Park H, Shin D, Baek S, Choi M, Yu D. Adv Mater 2013;25:2617–23.
385
[14] Ding B, Bardosova M, Povey I, Pemble ME, Romanov SG. Adv Funct Mater 2010;20:853–60. [15] Takahashi Y, Inui Y, Chihara M, Asano T, Terawaki R, Noda S. Nature 2013;498:470–4. [16] Liu GQ, Li L, Gong LX, Tang FL, Wang Q. Mater Lett 2012;68:466–8. [17] Liu GQ, Liu ZQ, Huang K, Chen YH, Li L, Tang FL, et al. Mater Lett 2013;93:42–4. [18] Liu ZQ, Feng TH, Dai QF, Wu LJ, Lan S. Chin Phys B 2009;18:2383–8. [19] Istrate E, Sargent EH. J Opt A 2002;4:S242. [20] Tomljenovic-Hanic S, Martijn de Sterke C, Steel MJ. Opt Express 2006;14:12451–6. [21] Liu ZQ, Liu GQ, Zhou H, Liu X, Huang K, Chen Y. Nanotechnology 2013;24:155203. [22] Farcau C, Astilean S. J Opt A 2007;9:S345–9.