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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 23 — Nov. 18, 2013
  • pp: 28083–28094
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A high throughput supra-wavelength plasmonic bull’s eye photon sorter spatially and spectrally multiplexed on silica optical fiber facet

Hesam Edin Arabi, Hang-Eun Joe, Tavakol Nazari, Byung-Kwon Min, and Kyunghwan Oh  »View Author Affiliations


Optics Express, Vol. 21, Issue 23, pp. 28083-28094 (2013)
http://dx.doi.org/10.1364/OE.21.028083


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Abstract

This paper presents a plasmonic bull’s eye consisting of a micron-sized hole and a concentric nano-antenna metallic ring surrounded by periodic circular grooves on a thin gold film. The unique metallic nano-ring imbedded in the supra-wavelength-sized hole acts as an amplifying and filtering component to simultaneously provide a significantly lower spectral noise and a higher power transmission at the resonance wavelength, in comparison to prior sub-wavelength bull’s eyes. Systematic numerical analyses based on finite-difference time-domain method were carried out to find the impacts of the structural parameters. Experimentally we integrated three proposed plasmonic structure on a cleaved facet of an optical fiber that can act as a spatially and spectrally multiplexed photon sorter. Transmission characteristics of the proposed devices were characterized in terms of the spectral response and signal to noise ratio. Potential applications of the fiber optic photon sorter were also discussed.

© 2013 Optical Society of America

1. Introduction

The surface plasmon polaritons (SPPs) on a hole array in metal film have generated intense research interests due to their unique enhanced optical transmission (EOT) and sub-wavelength scalability in optoelectronics [1

1. C. Genet and T. W. Ebbesen, “Light in tiny holes,” Nature 445(7123), 39–46 (2007). [CrossRef] [PubMed]

]. In recent years, plasmonic structures have rapidly expanded their applications in biosensing [2

2. K. Byun, “Development of nanostructured plasmonic substrates for enhanced optical biosensing,” J. Opt. Soc. Korea 14(2), 65–76 (2010). [CrossRef]

], nano-scale networking [3

3. A. Dolatabady and N. Granpayeh, “All optical logic gates based on two dimensional plasmonic waveguides with nanodisk resonators,” J. Opt. Soc. Korea 16(4), 432–442 (2012). [CrossRef]

], nano-optical trapping [4

4. M. L. Juan, M. Righini, and R. Quidant, “Plasmonic nano-optical twisters,” Nat. Photonics 5(6), 349–356 (2011). [CrossRef]

], nano-imaging, super-lensing [5

5. S. Kawata, Y. Inouye, and P. Verma, “Plasmonics for near-field nano-imaging and superlensing,” Nat. Photonics 3(7), 388–394 (2009). [CrossRef]

], high efficient LEDs, solar cells [6

6. K. Okamoto and Y. Kawakami, “Nano structure controlled plasmonics towards high-efficiency light-emitting diodes and solar cells,” Renewable Energy Proceeding (2010).

], and spectral imaging [7

7. E. Laux, C. Genet, T. Skauli, and T. W. Ebbesen, “Plasmonic photon sorters for spectral and polarimetric imaging,” Nat. Photonics 2(3), 161–164 (2008). [CrossRef]

], to name a few. In the context of spectral imaging, the sub-wavelength-sized bull’s eye (sub-λ-BE) consisting of a central nano scale hole flanked by concentric periodic circular grooves on a metal film, has been of particular interests [8

8. S. Carretero-Palacios, O. Mahboub, F. J. Garcia-Vidal, L. Martin-Moreno, S. G. Rodrigo, C. Genet, and T. W. Ebbesen, “Mechanisms for extraordinary optical transmission through bull’s eye structures,” Opt. Express 19(11), 10429–10442 (2011). [CrossRef] [PubMed]

]. In prior sub-λ-BEs, the hole diameter was kept smaller than the resonance wavelength and the periodic circular grooves act like an antenna for the incoming light by converting it to SPPs to result in the resonant EOT through the hole. Detailed structural optimization and subsequent optical characteristics of sub-λ-BEs have been carried out in prior reports [8

8. S. Carretero-Palacios, O. Mahboub, F. J. Garcia-Vidal, L. Martin-Moreno, S. G. Rodrigo, C. Genet, and T. W. Ebbesen, “Mechanisms for extraordinary optical transmission through bull’s eye structures,” Opt. Express 19(11), 10429–10442 (2011). [CrossRef] [PubMed]

10

10. F. F. Ren, K. W. Ang, J. Ye, M. Yu, G. Q. Lo, and D. L. Kwong, “Split bull’s eye shaped aluminum antenna for plasmon-enhanced nanometer scale germanium photodetector,” Nano Lett. 11(3), 1289–1293 (2011). [CrossRef] [PubMed]

]. Despite flexible tunability of EOT resonant wavelength, conventional sub-λ-BEs have an inherent shortcoming of very low power transmission due to their sub-wavelength daperture size [8

8. S. Carretero-Palacios, O. Mahboub, F. J. Garcia-Vidal, L. Martin-Moreno, S. G. Rodrigo, C. Genet, and T. W. Ebbesen, “Mechanisms for extraordinary optical transmission through bull’s eye structures,” Opt. Express 19(11), 10429–10442 (2011). [CrossRef] [PubMed]

, 9

9. O. Mahboub, S. C. Palacios, C. Genet, F. J. Garcia-Vidal, S. G. Rodrigo, L. Martin-Moreno, and T. W. Ebbesen, “Optimization of bull’s eye structures for transmission enhancement,” Opt. Express 18(11), 11292–11299 (2010). [CrossRef] [PubMed]

].This paper presents a new category of bull’s eyes that can provide much higher transmission compare to sub-λ-BEs for practical applications.

In this study we introduce a new category of the plasmonic bull’s eye, which consists of a central hole with a supra-wavelength scale diameter exceeding 1μm with a metallic nano-ring antenna concentrically imbedded there within, along with periodic circular grooves on a gold thin film deposited on the facet of a silica optical fiber. Firstly we numerically proved that the proposed supra-wavelength bull’s eye (supra-λ-BE) structure can provide a larger EOT throughput with a significantly less spectral noise by an optimal balance between the functions of the larger central hole and the nano-antenna ring. We further fabricated a single supra-λ-BE and then three supra-λ-BEs multiplexed on the facet of a hard polymer cladding fiber (HPCF) to investigate their optical characteristics, for the first time.

Metallic nano-antennas have shown unique optical properties including the optical excitation of surface plasmon resonance, strong localization of energy at nanometer scale, enhancement of electric field, and resonance wavelength tunability [11

11. N. Large, J. Aizpurua, V. K. Lin, S. L. Teo, R. Marty, S. Tripathy, and A. Mlayah, “Plasmonic properties of gold ring-disk nano-resonators: fine shape details matter,” Opt. Express 19(6), 5587–5595 (2011). [CrossRef] [PubMed]

,12

12. A. Moreau, G. Granet, F. I. Baida, and D. Van Labeke, “Light transmission by subwavelength square coaxial aperture arrays in metallic films,” Opt. Express 11(10), 1131–1136 (2003). [CrossRef] [PubMed]

]. Among the metallic nano-antennas, circular rings have been center of research interests because they exhibited a strong localized surface plasmon resonance which can be spectrally tuned simply by varying the ring thickness and its radius [13

13. J. Aizpurua, P. Hanarp, D. S. Sutherland, M. Käll, G. W. Bryant, and F. J. García de Abajo, “Optical properties of gold nanorings,” Phys. Rev. Lett. 90(5), 057401 (2003). [CrossRef] [PubMed]

]. Nano-antenna rings are known to be polarization-insensitive, which would make a good match with polarization-insensitive structures such as bull’s eyes.

2. Design and characterization

In the proposed supra-λ-BE shown in Fig. 1(a), the total transmission intensity is given by [19

19. H. Lezec and T. Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express 12(16), 3629–3651 (2004). [CrossRef] [PubMed]

];
Tc(λ)=A1(λ;nsilica,L)TH(λ;nair,d,h)A2(λ;nair,L)fc(λ;NA,L)
(1)
A1 and A2 represent the plasmonic features of the bull’s eye. TH represents intrinsic transmission of the hole. fc is the fraction of the total power collected by the objective of the detector. Here A1 is the modulation function corresponding to the interference between SPPs on the Gold/Silica interface and incident light. A2 corresponds to the interference between SPPs on Gold/Air interface and light emerging from the central hole. For simplicity the lateral parameters of the circular grooves (a,p,w,s) in Fig. 1(b) are labeled as L. The refractive indices of silica and air are denoted by nsilica and nair respectively.

In this study we applied two strategies to increase the total EOT throughput at the resonance wavelength, Tc(λr). Firstly, the intrinsic transmission of the hole, TH(λr), was enhanced by both increasing the hole size and placing an optimal metallic nano-antenna ring as shown in Fig. 1(b). Secondly, modulation functions A1(λr) and A2(λr) were maximized by optimizing the groove parameters, L [9

9. O. Mahboub, S. C. Palacios, C. Genet, F. J. Garcia-Vidal, S. G. Rodrigo, L. Martin-Moreno, and T. W. Ebbesen, “Optimization of bull’s eye structures for transmission enhancement,” Opt. Express 18(11), 11292–11299 (2010). [CrossRef] [PubMed]

].

2.1 Aperture design

In prior sub-λ-BEs, the hole diameter defines the cut-off wavelength and TH(λr)is maximized only if the hole size, d, remains in the sub-wavelength range near d~λr/2 [9

9. O. Mahboub, S. C. Palacios, C. Genet, F. J. Garcia-Vidal, S. G. Rodrigo, L. Martin-Moreno, and T. W. Ebbesen, “Optimization of bull’s eye structures for transmission enhancement,” Opt. Express 18(11), 11292–11299 (2010). [CrossRef] [PubMed]

]. In contrast, in this supra-λ-BE we increased the hole size as large as d~2λr. However, there is a complicated trade-off between the plasmonic features (A1 and A2), and the aperture feature (TH). It is well-known that the larger the hole size of a bull’s eye is, the lower the impact of SPPs coupling becomes [8

8. S. Carretero-Palacios, O. Mahboub, F. J. Garcia-Vidal, L. Martin-Moreno, S. G. Rodrigo, C. Genet, and T. W. Ebbesen, “Mechanisms for extraordinary optical transmission through bull’s eye structures,” Opt. Express 19(11), 10429–10442 (2011). [CrossRef] [PubMed]

, 9

9. O. Mahboub, S. C. Palacios, C. Genet, F. J. Garcia-Vidal, S. G. Rodrigo, L. Martin-Moreno, and T. W. Ebbesen, “Optimization of bull’s eye structures for transmission enhancement,” Opt. Express 18(11), 11292–11299 (2010). [CrossRef] [PubMed]

, 20

20. S. H. Chang, S. Gray, and G. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]

]. As the hole size increases the plasmonic local dipole magnitude emerging on the rim of the hole decreases, to result in a weaker coupling between the directly transmitted light and SPPs [20

20. S. H. Chang, S. Gray, and G. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]

]. We used a commercial finite difference time domain (FDTD) simulation package (Lumerical Solutions Inc.), to find the impact of the hole size on transmission and the results are summarized in Fig. 2
Fig. 2 The optical power transmission through a bull’s eye (grooves number = 7, p = 500 nm, a = 1600 nm, s = 120 nm, w = 250 nm, h = 300 nm, d = 0.5~2.0 μm). The transmission spectra were normalized to that of a grooveless bull’s eye with d = 1.5 μm.
. Here we fixed the groove parameters as p = 500 nm, a = 1600 nm s = 120 nm, w = 250 nm, h = 300 nm, number of grooves = 7, and varied only the hole diameter d = 0.5~2.0 μm. Note that in Fig. 2 we did not include the nano-antenna ring yet. The transmission spectra are normalized to that of a grooveless bull’s eye with d = 1.5 μm.

In the sub-λ-BE regime with d = 0.5 μm (black curve in Fig. 2), the plasmonic factors A1(λr) and A2(λr) strongly contributed to the EOT peak located near λr = 730 nm. Yet by increasing the hole size, TH shows a stronger contribution, with a decreasing contrast of the EOT peak against the overall transmission background (green and red curves in Fig. 2). If the hole size further exceeds 1.5 μm, d>2.5λr, the plasmonic feature is lost as in the top blue curve in Fig. 2.

Figure 3
Fig. 3 Electric field intensity at 30 nm above a bull’s eye (grooves number = 7, p = 500 nm, a = 1600 nm, s = 120 nm, w = 250 nm, h = 300 nm),with hole size of (a) 0.5μm, (b) 1.5μm, (c) 2.0μm. Solid and dashed curves represent the intensities of the bull’s eye with and without the grooves respectively.
illustrates the contribution of TH as well as plasmonic parameters to EOT at different hole sizes. Solid curves in Fig. 3 are electric field intensities at 30nm above the bull’s eye, and dashed curves are those of the grooveless bull’s eye representing electric field intensities of a weakly plasmonic apertures (A1 and A2 <<TH). As red dashed curves indicated in Fig. 3(a) and 3(c), TH has less contribution in d = 0.5μm, and more dominant contribution in d = 2.0μm. However, at the hole size of d = 1.5μm there is a trade-off between TH and plasmonic parameters to give rise to an unique electric field intensity that can be further optimized by changing structural parameters.

In order to simultaneously suppress the spectral noise and increase the EOT peak, we proposed a new idea to imbed a nano-antenna ring inside the supra-wavelength-size hole, as shown in the inset of Fig. 4
Fig. 4 The normalized power transmission of a supra-λ-BE without the nano-antenna ring (blue curve) and with the nano-antenna ring (red curve). (grooves number = 11, p = 500 nm, a = 1600 nm, s = 120 nm, w = 250 nm, d = 1.5 μm, h = 300 nm, c = 130 nm, and r = 240 nm).
.

In theoretical analyses, we found that the nano-antenna ring can increase the EOT peak about 20%, while reduces the background transmission about 22~52%. See red curve in Fig. 4. The nano-antenna ring plays the key role of amplifying and filtering in the supra-λ-BE.

To better understand the role of the nano-antenna ring in the supra-λ-BE, the intensity profile of light was investigated along the propagation axis, z, at the resonance (Fig. 5(a)
Fig. 5 The electric filed intensity profile along the propagation axis, z, for the supra-λ-BE (a) at the resonance wavelength, λr = 721 nm (b) at a non-resonance wavelength, λ = 689 nm. Here the panels i (i’) and ii (ii’) present the case without and with the nano-antenna ring, respectively. (c) The intensity distribution of the beam rendered by the supra-λ-BE for the cases of i, ii, i', and ii' at z = 1μm. Structural parameters were: grooves number = 12, p = 500 nm, a = 1600 nm, s = 120 nm, w = 250 nm, d = 1.5 μm, h = 300 nm, c = 130 nm, and r = 240 nm.
) and a non-resonance wavelength (Fig. 5(b)) using FDTD. As shown in Fig. 5(a), in Silica/Gold interface, the electromagnetic wave reemitted by nano-antenna ring at the resonance wavelength of λr = 721nm (panel ii) is in-phase with that of the bull’s eye resulting in a stronger filed enhancement compare to the case without the nano-antenna ring (panel i). The intensity distribution in panel ii indicate that both sides of the nano-antenna ring contribute to the electric field enhancement. Here the field enhancement in Air/Gold interface refers to the solely electromagnetic coupling between the inner and outer walls of the ring [13

13. J. Aizpurua, P. Hanarp, D. S. Sutherland, M. Käll, G. W. Bryant, and F. J. García de Abajo, “Optical properties of gold nanorings,” Phys. Rev. Lett. 90(5), 057401 (2003). [CrossRef] [PubMed]

].

On the contrary, as in Fig. 5(b), at a non-resonance wavelength λ = 689 nm, the electromagnetic wave reemitted by the nano-antenna ring is not phase-matched with that of the bull’s eye (panel ii') giving significantly less throughput than the case without nano-antenna ring (panel i'). Figure 5(c) depicts more clearly the intensity profiles of the beam rendered by the supra-λ-BE for the cases of i, ii, i', and ii' at the distance of z = 1μm. The comparison between i and ii in Fig. 5(c) confirms that the nano-antenna plays an amplifying role to boost the EOT at the resonance wavelength. Comparison between the intensity profile of i' and ii' in Fig. 5(c) also indicates unique role of spectral filtering of the nano-antenna ring to suppress transmission at non-resonance wavelengths.

Figure 6
Fig. 6 The electric filed intensity profile in the Silica/Gold interface of the structures showed in Fig. 5(a) and 5(b), at (a) the resonance wavelength, λr = 721 nm (b) at a non-resonance wavelength, λ = 689 nm. The shaded area illustrates the position of the central hole.
demonstrates more clearly the mechanism of destructive and constructive electric field interface of the structures in panel (ii) and (ii'). The shaded area in Fig. 6 illustrates the position of the central hole. As shown in Fig. 6(a) the constructive interference of electric fields in Silica/Gold interface results in a stronger field intensity distribution, the red dashed line, near the rim of the hole, x = 0.75~2μm, compared to that of the structure in panel (i) (blue solid curve). However, in Fig. 6(b) the destructive interference at a non-resonance wavelength results in a weaker electric filed intensity, red dashed curve, on the rim compared to that of the structure in panel (i') (blue solid curve).

Further numerical study on nano-antenna rings showed that the filtering strength of the supra-λ-BE can be maximized by properly adjusting the nano-ring parameters (c:thickness and, r: inner radius). Figure 7
Fig. 7 The normalized transmission of EOT peak (solid lines) and its spectral averaged background noise (dashed lines) as a function of (a) r: inner radius, and (b) c: thickness of the nano-antenna ring. In (a), c = 130nm. In (b), r = 240nm (for p = 500nm) and r = 270nm (for p = 450nm). Other grooves parameters are a = 1600nm, s = 120nm, w = 250nm, h = 300nm, and groove’s number = 7.
shows how the normalized transmission behaves as we vary these nano-ring parameters. The solid lines are the EOT intensities and the dashed lines are the averaged background spectral noise. Here we chose two periodicity p = 450, 500nm. The most efficient spectral filtering could be obtained when the contrast between EOT and the averaged noise is maximized. As Fig. 7(a) and 7(b) indicate the transmission contrast of the supra-λ-BEs can be further maximized with the conditions 1) c = 130nm, r = 240nm for a supra-λ-BE with p = 500nm, and c = 130nm, r = 270nm for p = 450nm. These results indicated that the ring radius should be increased when the grooves period was decreased in order to get maximum transmission contrast.

2.2 Bull's eye design

Tc(λr) was further maximized by the modulation functions A1(λr) and A2(λr) with optimal lateral parameters (L: a, p, w, s). FDTD simulation results showed that at the resonance wavelength of λr = 620~740 nm the maximum transmission was obtained when p = 420~500 nm, w = 250~300 nm, and s = 120 nm, satisfying the optimal approximations: w/p~0.5, s/w~0.4 as already confirmed in prior sub-λ-BEs [9

9. O. Mahboub, S. C. Palacios, C. Genet, F. J. Garcia-Vidal, S. G. Rodrigo, L. Martin-Moreno, and T. W. Ebbesen, “Optimization of bull’s eye structures for transmission enhancement,” Opt. Express 18(11), 11292–11299 (2010). [CrossRef] [PubMed]

]. Spacing parameter, a, was known to play a key role in the constructive coupling of SPPs [8

8. S. Carretero-Palacios, O. Mahboub, F. J. Garcia-Vidal, L. Martin-Moreno, S. G. Rodrigo, C. Genet, and T. W. Ebbesen, “Mechanisms for extraordinary optical transmission through bull’s eye structures,” Opt. Express 19(11), 10429–10442 (2011). [CrossRef] [PubMed]

]. Figure 8
Fig. 8 EOT peak intensity variation as a function of the spacing parameter, a, in the proposed supra-λ-BE (grooves number = 7, a = 1500 nm, s = 120 nm, w = 250 nm, d = 1.5 μm, h = 300 nm, c = 130 nm, and r = 240 nm) for two groove periods of p = 500 nm and 450 nm.
shows the EOT peak variation as a function of the spacing parameter, a, for two different groove periods, p = 500 nm and 450 nm. Maxima in Fig. 8 indicate that the constructive interference of SPPs with transmitted light can be maximized at an optimal spacing parameter (a = amax), which are summarized in Table 1

Table 1. Resonance wavelength λr, SPP wavelength λSP, and optimal spacing parameter amax for different groove period, p. λSP at Silica/Gold interface was obtained using both the dispersion relation, Eq. (2) and approximation, Eq. (3). The rest of parameters are the same as in Fig. 4.

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. The wavelength of SPPs, λSP, traveling in the Gold/Silica interface at resonance is given by a dispersion relation [10

10. F. F. Ren, K. W. Ang, J. Ye, M. Yu, G. Q. Lo, and D. L. Kwong, “Split bull’s eye shaped aluminum antenna for plasmon-enhanced nanometer scale germanium photodetector,” Nano Lett. 11(3), 1289–1293 (2011). [CrossRef] [PubMed]

]:

λSP=λrεg+εsεgεs
(2)

Here εg and εs represent the frequency dependent permittivity of the gold film and the silica substrate respectively. As shown in Table1, we could confirm an optimal spacing parameter approximation as in prior sub-λ-Bes [8

8. S. Carretero-Palacios, O. Mahboub, F. J. Garcia-Vidal, L. Martin-Moreno, S. G. Rodrigo, C. Genet, and T. W. Ebbesen, “Mechanisms for extraordinary optical transmission through bull’s eye structures,” Opt. Express 19(11), 10429–10442 (2011). [CrossRef] [PubMed]

]:
λSP2amax2m
(3)
where m is an integer.

3. Device fabrication

Figure 9
Fig. 9 Schematic fabrication process steps for inscribing the single supra-λ-BE on the fiber facet.
schematically shows the fabrication process of the single supra-λ-BE on silica optical fiber facet. HPCF was cleaved vertically using an ultrasonic cleaver to prepare an optical quality facet. A 150-nm-thick sacrificial gold layer was deposited on the HPCF facet using a thermal evaporation technique to overcome charging problem in the following focused ion beam (FIB) process. Circular grooves with the depth of 120 nm were milled on the fiber facet using a FIB setup (SII Nanotechnology SMI 3050). The sacrificial layer on the fiber was wet-etched by using Potassium Iodide (KI) solution which does not have any reaction with silica, and then the prepared facet was re-coated by 300-nm-thick gold film. Finally the central supra-λ hole and the nano-antenna ring were inscribed at the center of the grooves using FIB.

4. Experiments and results

Figure 10(a)
Fig. 10 (a) FIB micrographs of a supra-λ-BE (grooves number = 11, p = 500 nm, a = 1600 nm, w = 250 nm, s = 120 nm, d = 1.5 μm, h = 300 nm, c = 130 nm, r = 240 nm) fabricated on the metalized end-facet of a HPCF. Inset is the micrograph of the nano-antenna ring. (b) The normalized transmission spectra of the supra-λ-BE: experimentally measured spectrum (black solid curve). The blue dashed and red dotted curves are simulation results with and without nano-antenna ring, respectively. The transmission contrasts of EOT peaks against the background were 6.1 dB and 6.7 dB for theoretical and experimental observation, respectively.
shows the FIB micrograph of a fabricated device with a single supra-λ-BE on fiber, where the inset diagram magnifies the central hole and nano-antenna ring. In order to measure the transmission characteristics of the proposed device, a white light source was coupled to the HPCF’s input end. The normalized transmission spectrum of the supra-λ-BE is shown in Fig. 10(b) (black solid curve), measured by a UV-visible spectrum analyzer (Maya 2000), along with simulation results (red dotted and blue dashed curves). An EOT peak at 725 nm was observed and correlated to SPP sat the Gold/Silica interface, consistent to Fig. 4 and Table 1. In contrast, SPPs at the Gold/Air interface had a negligible influence on EOT peak power, since the evanescent waves at Gold/Air interface are exited through indirect illumination of the incident light. Additionally, due to asymmetry of ambient dielectrics on two sides of the gold film the resonant frequency of SPP in Air/Gold interface and that of the Silica/Gold doesn’t coincide resulting in low contribution of the Air/Gold interface to EOT [21

21. A. Krishnan, T. Thio, T. J. Kim, H. J. Lezec, T. W. Ebbesen, P. A. Wolff, J. Pendry, L. Martin-Moreno, and F. J. Garcia-Vidal, “Evanescently coupled resonance in surface plasmon enhanced transmission,” Opt. Commun. 200(1-6), 1–7 (2001). [CrossRef]

]. Other broad peak observed in the spectral range λ<725 nm are attributed to higher order SPP modes [22

22. T. Thio, K. M. Pellerin, R. A. Linke, H. J. Lezec, and T. W. Ebbesen, “Enhanced light transmission through a single subwavelength aperture,” Opt. Lett. 26(24), 1972–1974 (2001). [CrossRef] [PubMed]

]. The background noise in the transmission observed in this range is known to originate from the defects in the grooves [23

23. B. Jia, H. Shi, J. Li, Y. Fu, C. Du, and M. Gu, “Near-field visualization of focal depth modulation by step corrugated plasmonic slits,” Appl. Phys. Lett. 94(15), 151912 (2009). [CrossRef]

]. Using FDTD analyses, the EOT peak was predicted at 721 nm (dashed blue curve in Fig. 10(b)) showing a good agreement with the experimental measurements.

In order to quantitatively investigate the contribution of nano-antenna ring to EOT, we defined ‘transmission contrast’, which is the difference in the dB scale between the EOT peak intensity and that of the background in the spectral domain. In Fig. 10(b), the transmission contrast in the fabricated supra-λ-BE with the nano-antenna ring was measured to be 6.7 dB, which is in a good agreement with 6.1 dB predicted by FDTD simulation. While the transmission contrast in the absence of the ring is predicted as low as 3.7 dB (see red dotted curve).

Having successfully established the fabrication process for the single supra-λ-BE on fiber, we further imbedded three distinctive supra-λ-BEs on the HPCF facet, in order to realize a spatially and spectrally multiplexed plasmonic photon sorter on fiber. Figure 11(a)
Fig. 11 (a) A plasmonic photon sorter fabricated on the end-facet of a HPCF. (b) Microscopic image of the photon sorter when white light was launched in to fiber. (c)FIB micrograph of the photon sorter composed of three distinctive supra-λ-BEs spatially and spectrally multiplexed on the optical fiber facet. (d) The transmission spectra of the plasmonic photon sorter. Black solid line is for the measured data and three peaks 1~3 are attributed to EOTs of three supra-λ-BEs. The dotted lines are simulation results base on FDTD.
and 11(c) illustrate FIB micrographs of a fabricated three supra-λ-BEs on the end-facet of a HPCF. Figure 11(b) shows the end facet of the fiber when white light was launched into the fiber . Three supra-λ-BEs were spatially multiplexed in a linear array with the pitch of 25 μm on the facet of optical fiber, without any overlapping grooves as shown in Fig. 11(c). Note that this linear structure is different from prior report based on a free standing foil where the sub-λ-BEs were arranged in a triangle with significantly overlapping the grooves [7

7. E. Laux, C. Genet, T. Skauli, and T. W. Ebbesen, “Plasmonic photon sorters for spectral and polarimetric imaging,” Nat. Photonics 2(3), 161–164 (2008). [CrossRef]

]. Detailed structural parameters are summarized in Table 2

Table 2. Structural parameters of three supra-λ-BEs on the fiber optic photon sorter.

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.

The transmission spectrum of the fabricated photon sorter was measured by coupling a white light source to the HPCF input end and the results are summarized in the black solid line of Fig. 11(d). In experiments, we measured three strong peaks denoted by 1, 2, and 3 as shown in Fig. 11(d) and they are attributed to the EOT resonances of three supra-λ-BEs. The FDTD simulations were carried out for each supra-λ-BE and the results are overlaid in dotted lines in Fig. 11(d). The experimentally measured EOT resonance wavelengths are listed in Table 3

Table 3. Spectral characteristics of three supra-λ-BEs on the fiber optic photon sorter. Numbers in the parenthesis were numerically obtained using FDTD.

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, along with corresponding simulation results in the parentheses. The measured spectral positions of these EOT peaks showed a fair agreement with the FDTD simulation results and we could confirm that spatially and spectrally multiplexing of supra-λ-BEs were realized on the fiber facet, for the first time. It is also very noteworthy to find that transmission contrast for each EOT also showed a very good agreement between the measurements and FDTD simulation as in Table 3. The difference between the experiments and the simulation are mainly attributed to inevitable structural imperfections introduced in the fabrication processes. Interestingly in the experiment a higher normalized transmission at EOT peaks was observed (3.4~3.8 in the normalized scale on the right axis of Fig. 11(d)) than the numerical prediction (1.6~2.4 in the normalized scale on the left axis of Fig. 11(d)).

Each EOT showed a Gaussian-like beam with the beam diameter of ~2 μm measured at the axial distance of ~1 μm from the exit surface, which is also consistent to FDTD simulations in Fig. 5(c). The three beams were spatially separable within this range.

The spectral domain (627~734 nm) of the device corresponds to the responsive range of Si photo-detector, and the full width at half maximum beam diameter of ~2 μm is highly comparable to Si photonic waveguide devices [24

24. M. J. R. Heck, H. Chen, A. W. Fang, B. R. Koch, D. Liang, H. Park, M. N. Sysak, and J. E. Bowers, “Hybrid silicon photonics for optical interconnects,” IEEE J. Sel. Top. Quantum Electron. 17(2), 333–346 (2011). [CrossRef]

]. In terms of this spectral domain matching and beam diameter, the proposed device can have a high compatibility to Si photonics and the authors are investigating feasibility of further integration of the device with Si waveguides and photo-detectors for optical interconnection applications.

5. Conclusion

In summary, we both theoretically and experimentally demonstrated a new potential solution to overcome the fundamental bottleneck of prior sub-wavelength bull’s eye devices: inherently low transmission. To challenge this issue we proposed a unique supra-λ-BE structure, which is composed of the central hole enlarged to ~2 times of wavelength and a concentric nano-antenna ring imbedded there within. Optimizing the structural parameters, we theoretically predicted that the supra-λ-BE can provide significantly increased transmission intensity by more than 20% and enhanced peak-to-background ratio over 6 dB at the SPP resonances. Single supra-λ-BE was firstly inscribed on the HPCF facet and we confirmed experimentally the impacts of proposed structure by observing enhanced transmission and peak-to-background ratio. We then further integrated three distinctive supra-λ-BEs to form a 1 × 3 array on the fiber facet multiplexing plasmonic resonance both spectrally and spatially. This fiber-optic plasmonic photon sorter showed enhanced optical transmission peaks in the spectral range from 627~734 nm with a beam diameter of ~2 μm, which are highly compatible to silicon photonic devices. Further applications in optical interconnection in silicon photonics are being pursued by the authors.

Acknowledgment

This work was supported in part by the Brain Korea 21Project, in part by the NRF of Korea and a grant funded by the Korea government (MEST) (2011-00181613, 2012M3A7 B4049800), in part by the Seoul R&BD Program (PA110081), in part by the Samsung Electro-Mechanics (2013-8-1221), and in part by the LG Display (2011-8-2160).

References and links

1.

C. Genet and T. W. Ebbesen, “Light in tiny holes,” Nature 445(7123), 39–46 (2007). [CrossRef] [PubMed]

2.

K. Byun, “Development of nanostructured plasmonic substrates for enhanced optical biosensing,” J. Opt. Soc. Korea 14(2), 65–76 (2010). [CrossRef]

3.

A. Dolatabady and N. Granpayeh, “All optical logic gates based on two dimensional plasmonic waveguides with nanodisk resonators,” J. Opt. Soc. Korea 16(4), 432–442 (2012). [CrossRef]

4.

M. L. Juan, M. Righini, and R. Quidant, “Plasmonic nano-optical twisters,” Nat. Photonics 5(6), 349–356 (2011). [CrossRef]

5.

S. Kawata, Y. Inouye, and P. Verma, “Plasmonics for near-field nano-imaging and superlensing,” Nat. Photonics 3(7), 388–394 (2009). [CrossRef]

6.

K. Okamoto and Y. Kawakami, “Nano structure controlled plasmonics towards high-efficiency light-emitting diodes and solar cells,” Renewable Energy Proceeding (2010).

7.

E. Laux, C. Genet, T. Skauli, and T. W. Ebbesen, “Plasmonic photon sorters for spectral and polarimetric imaging,” Nat. Photonics 2(3), 161–164 (2008). [CrossRef]

8.

S. Carretero-Palacios, O. Mahboub, F. J. Garcia-Vidal, L. Martin-Moreno, S. G. Rodrigo, C. Genet, and T. W. Ebbesen, “Mechanisms for extraordinary optical transmission through bull’s eye structures,” Opt. Express 19(11), 10429–10442 (2011). [CrossRef] [PubMed]

9.

O. Mahboub, S. C. Palacios, C. Genet, F. J. Garcia-Vidal, S. G. Rodrigo, L. Martin-Moreno, and T. W. Ebbesen, “Optimization of bull’s eye structures for transmission enhancement,” Opt. Express 18(11), 11292–11299 (2010). [CrossRef] [PubMed]

10.

F. F. Ren, K. W. Ang, J. Ye, M. Yu, G. Q. Lo, and D. L. Kwong, “Split bull’s eye shaped aluminum antenna for plasmon-enhanced nanometer scale germanium photodetector,” Nano Lett. 11(3), 1289–1293 (2011). [CrossRef] [PubMed]

11.

N. Large, J. Aizpurua, V. K. Lin, S. L. Teo, R. Marty, S. Tripathy, and A. Mlayah, “Plasmonic properties of gold ring-disk nano-resonators: fine shape details matter,” Opt. Express 19(6), 5587–5595 (2011). [CrossRef] [PubMed]

12.

A. Moreau, G. Granet, F. I. Baida, and D. Van Labeke, “Light transmission by subwavelength square coaxial aperture arrays in metallic films,” Opt. Express 11(10), 1131–1136 (2003). [CrossRef] [PubMed]

13.

J. Aizpurua, P. Hanarp, D. S. Sutherland, M. Käll, G. W. Bryant, and F. J. García de Abajo, “Optical properties of gold nanorings,” Phys. Rev. Lett. 90(5), 057401 (2003). [CrossRef] [PubMed]

14.

L. A. Dunbar, M. Guillaumée, F. de León-Pérez, C. Santschi, E. Grenet, R. Eckert, F. López-Tejeira, F. J. García-Vidal, L. Martín-Moreno, and R. P. Stanley, “Enhanced transmission from a single subwavelength slit aperture surrounded by grooves on a standard detector,” Appl. Phys. Lett. 95(1), 011113 (2009). [CrossRef]

15.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002). [CrossRef] [PubMed]

16.

A. Dhawan and J. Muth, “Engineering surface plasmon based fiber-optic sensors,” Mater. Sci. Eng. B 149(3), 237–241 (2008). [CrossRef]

17.

S. Koehl, A. Liu, and M. Paniccia, “Integrated silicon photonics: Harnessing the data explosion,” Opt. Photon. News 22, 24–29 (2011). [CrossRef]

18.

A. Alduino, L. Liao, R. Jones, M. Morse, B. Kim, W. Lo, J. Basak, B. Koch, H. Liu, H. Rong, M. Sysak, C. Krause, R. Saba, D. Lazar, L. Horwitz, R. Bar, S. Litski, A. Liu, K. Sullivan, O. Dosunmu, N. Na, T. Yin, F. Haubensack, I. Hsieh, J. Heck, R. Beatty, H. Park, J. Bovington, S. Lee, H. Nguyen, H. Au, K. Nguyen, P. Merani, M. Hakami, and M. Paniccia, “Demonstration of a high speed 4-channel integrated silicon photonics WDM link with hybrid silicon lasers,” in Integrated Photonics Research, Silicon and Nanophotonics and Photonics in Switching, OSA Technical Digest (CD), Optical Society of America(2010). http://www.opticsinfobase.org/abstract.cfm?URI=IPRSN-2010-PDIWI5 [CrossRef]

19.

H. Lezec and T. Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express 12(16), 3629–3651 (2004). [CrossRef] [PubMed]

20.

S. H. Chang, S. Gray, and G. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]

21.

A. Krishnan, T. Thio, T. J. Kim, H. J. Lezec, T. W. Ebbesen, P. A. Wolff, J. Pendry, L. Martin-Moreno, and F. J. Garcia-Vidal, “Evanescently coupled resonance in surface plasmon enhanced transmission,” Opt. Commun. 200(1-6), 1–7 (2001). [CrossRef]

22.

T. Thio, K. M. Pellerin, R. A. Linke, H. J. Lezec, and T. W. Ebbesen, “Enhanced light transmission through a single subwavelength aperture,” Opt. Lett. 26(24), 1972–1974 (2001). [CrossRef] [PubMed]

23.

B. Jia, H. Shi, J. Li, Y. Fu, C. Du, and M. Gu, “Near-field visualization of focal depth modulation by step corrugated plasmonic slits,” Appl. Phys. Lett. 94(15), 151912 (2009). [CrossRef]

24.

M. J. R. Heck, H. Chen, A. W. Fang, B. R. Koch, D. Liang, H. Park, M. N. Sysak, and J. E. Bowers, “Hybrid silicon photonics for optical interconnects,” IEEE J. Sel. Top. Quantum Electron. 17(2), 333–346 (2011). [CrossRef]

OCIS Codes
(060.2310) Fiber optics and optical communications : Fiber optics
(130.3120) Integrated optics : Integrated optics devices
(240.6680) Optics at surfaces : Surface plasmons
(220.4241) Optical design and fabrication : Nanostructure fabrication
(310.6628) Thin films : Subwavelength structures, nanostructures

ToC Category:
Plasmonics

History
Original Manuscript: July 17, 2013
Revised Manuscript: October 4, 2013
Manuscript Accepted: October 29, 2013
Published: November 8, 2013

Citation
Hesam Edin Arabi, Hang-Eun Joe, Tavakol Nazari, Byung-Kwon Min, and Kyunghwan Oh, "A high throughput supra-wavelength plasmonic bull’s eye photon sorter spatially and spectrally multiplexed on silica optical fiber facet," Opt. Express 21, 28083-28094 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-23-28083


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References

  1. C.  Genet, T. W.  Ebbesen, “Light in tiny holes,” Nature 445(7123), 39–46 (2007). [CrossRef] [PubMed]
  2. K.  Byun, “Development of nanostructured plasmonic substrates for enhanced optical biosensing,” J. Opt. Soc. Korea 14(2), 65–76 (2010). [CrossRef]
  3. A.  Dolatabady, N.  Granpayeh, “All optical logic gates based on two dimensional plasmonic waveguides with nanodisk resonators,” J. Opt. Soc. Korea 16(4), 432–442 (2012). [CrossRef]
  4. M. L.  Juan, M.  Righini, R.  Quidant, “Plasmonic nano-optical twisters,” Nat. Photonics 5(6), 349–356 (2011). [CrossRef]
  5. S.  Kawata, Y.  Inouye, P.  Verma, “Plasmonics for near-field nano-imaging and superlensing,” Nat. Photonics 3(7), 388–394 (2009). [CrossRef]
  6. K. Okamoto and Y. Kawakami, “Nano structure controlled plasmonics towards high-efficiency light-emitting diodes and solar cells,” Renewable Energy Proceeding (2010).
  7. E.  Laux, C.  Genet, T.  Skauli, T. W.  Ebbesen, “Plasmonic photon sorters for spectral and polarimetric imaging,” Nat. Photonics 2(3), 161–164 (2008). [CrossRef]
  8. S.  Carretero-Palacios, O.  Mahboub, F. J.  Garcia-Vidal, L.  Martin-Moreno, S. G.  Rodrigo, C.  Genet, T. W.  Ebbesen, “Mechanisms for extraordinary optical transmission through bull’s eye structures,” Opt. Express 19(11), 10429–10442 (2011). [CrossRef] [PubMed]
  9. O.  Mahboub, S. C.  Palacios, C.  Genet, F. J.  Garcia-Vidal, S. G.  Rodrigo, L.  Martin-Moreno, T. W.  Ebbesen, “Optimization of bull’s eye structures for transmission enhancement,” Opt. Express 18(11), 11292–11299 (2010). [CrossRef] [PubMed]
  10. F. F.  Ren, K. W.  Ang, J.  Ye, M.  Yu, G. Q.  Lo, D. L.  Kwong, “Split bull’s eye shaped aluminum antenna for plasmon-enhanced nanometer scale germanium photodetector,” Nano Lett. 11(3), 1289–1293 (2011). [CrossRef] [PubMed]
  11. N.  Large, J.  Aizpurua, V. K.  Lin, S. L.  Teo, R.  Marty, S.  Tripathy, A.  Mlayah, “Plasmonic properties of gold ring-disk nano-resonators: fine shape details matter,” Opt. Express 19(6), 5587–5595 (2011). [CrossRef] [PubMed]
  12. A.  Moreau, G.  Granet, F. I.  Baida, D.  Van Labeke, “Light transmission by subwavelength square coaxial aperture arrays in metallic films,” Opt. Express 11(10), 1131–1136 (2003). [CrossRef] [PubMed]
  13. J.  Aizpurua, P.  Hanarp, D. S.  Sutherland, M.  Käll, G. W.  Bryant, F. J.  García de Abajo, “Optical properties of gold nanorings,” Phys. Rev. Lett. 90(5), 057401 (2003). [CrossRef] [PubMed]
  14. L. A.  Dunbar, M.  Guillaumée, F.  de León-Pérez, C.  Santschi, E.  Grenet, R.  Eckert, F.  López-Tejeira, F. J.  García-Vidal, L.  Martín-Moreno, R. P.  Stanley, “Enhanced transmission from a single subwavelength slit aperture surrounded by grooves on a standard detector,” Appl. Phys. Lett. 95(1), 011113 (2009). [CrossRef]
  15. H. J.  Lezec, A.  Degiron, E.  Devaux, R. A.  Linke, L.  Martin-Moreno, F. J.  Garcia-Vidal, T. W.  Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002). [CrossRef] [PubMed]
  16. A.  Dhawan, J.  Muth, “Engineering surface plasmon based fiber-optic sensors,” Mater. Sci. Eng. B 149(3), 237–241 (2008). [CrossRef]
  17. S.  Koehl, A.  Liu, M.  Paniccia, “Integrated silicon photonics: Harnessing the data explosion,” Opt. Photon. News 22, 24–29 (2011). [CrossRef]
  18. A. Alduino, L. Liao, R. Jones, M. Morse, B. Kim, W. Lo, J. Basak, B. Koch, H. Liu, H. Rong, M. Sysak, C. Krause, R. Saba, D. Lazar, L. Horwitz, R. Bar, S. Litski, A. Liu, K. Sullivan, O. Dosunmu, N. Na, T. Yin, F. Haubensack, I. Hsieh, J. Heck, R. Beatty, H. Park, J. Bovington, S. Lee, H. Nguyen, H. Au, K. Nguyen, P. Merani, M. Hakami, and M. Paniccia, “Demonstration of a high speed 4-channel integrated silicon photonics WDM link with hybrid silicon lasers,” in Integrated Photonics Research, Silicon and Nanophotonics and Photonics in Switching, OSA Technical Digest (CD), Optical Society of America(2010). http://www.opticsinfobase.org/abstract.cfm?URI=IPRSN-2010-PDIWI5 [CrossRef]
  19. H.  Lezec, T.  Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express 12(16), 3629–3651 (2004). [CrossRef] [PubMed]
  20. S. H.  Chang, S.  Gray, G.  Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]
  21. A.  Krishnan, T.  Thio, T. J.  Kim, H. J.  Lezec, T. W.  Ebbesen, P. A.  Wolff, J.  Pendry, L.  Martin-Moreno, F. J.  Garcia-Vidal, “Evanescently coupled resonance in surface plasmon enhanced transmission,” Opt. Commun. 200(1-6), 1–7 (2001). [CrossRef]
  22. T.  Thio, K. M.  Pellerin, R. A.  Linke, H. J.  Lezec, T. W.  Ebbesen, “Enhanced light transmission through a single subwavelength aperture,” Opt. Lett. 26(24), 1972–1974 (2001). [CrossRef] [PubMed]
  23. B.  Jia, H.  Shi, J.  Li, Y.  Fu, C.  Du, M.  Gu, “Near-field visualization of focal depth modulation by step corrugated plasmonic slits,” Appl. Phys. Lett. 94(15), 151912 (2009). [CrossRef]
  24. M. J. R.  Heck, H.  Chen, A. W.  Fang, B. R.  Koch, D.  Liang, H.  Park, M. N.  Sysak, J. E.  Bowers, “Hybrid silicon photonics for optical interconnects,” IEEE J. Sel. Top. Quantum Electron. 17(2), 333–346 (2011). [CrossRef]

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