3.6. Investigación Concluyente
3.6.1. Objetivos de la investigación cuantitativa
We would like to acknowledge the funding of TEN program from Canadian Institute for Photonic Innovations (CIPI). We acknowledge the technical support on the 3- D FDTD from Lumerical Inc. The simulations were performed using the parallel computing resources of WESTGRID and SHARCNET.
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(b)Figure 3.8: Effects of local dielectric environment at the surface of gold nanoparticles. (a) extinction spectra of different coating thickness. (b) spectral shift
References
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[3] S. Linden, J. Kuhl, and H. Giessen, “Controlling the interaction between light and gold nanoparticles: selective suppression of extinction,” Phys. Rev. Lett., vol. 86, no. 20, pp. 4688–4691, 2001.
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73 [9] J. Homola, J. Ctyroky, M. Skalsky, J. Hradilova, and P. Kolarova, “A surface plasmon resonance based integrated optical sensor,” Sensors and Actuators B: Chemical, vol. 39, no. 1-3, pp. 286 – 290, 1997.
[10] J. Dostalek, J. Ctyroky, J. Homola, E. Brynda, M. Skalsky, P. Nekvindova, J. Spirkova, J. Skvor, and J. Schrofel, “Surface plasmon resonance biosensor based on integrated optical waveguide,” Sensors and Actuators B: Chemical, vol. 76, no. 1-3, pp. 8 – 12, 2001.
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[12] M. Skorobogatiy and A. V. Kabashin, “Photon crystal waveguide-based surface plasmon resonance biosensor,” Applied Physics Letters, vol. 89, p. 143518, 2006. [13] P. Debackere, S. Scheerlinck, P. Bienstman, and R. Baets, “Surface plasmon interferometer in silicon-on-insulator: novel concept for an integrated biosensor: Reply,” Opt. Express, vol. 15, no. 21, pp. 13 651–13 653, 2007.
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Chapter 4
Periodic Arrays of Gold Nanodisks
Coupled with Evanescent Spectroscopy
1
4.1
Introduction
The extensive research interest in nanometer-dimension metallic nanoparticles has been mainly driven by their broad impact on the emerging disciplines of nanoengi- neering and nano-optics. Gold nanoparticles, in particular, have been the focus of numerous investigations in recent years because of the promises offered by their opti- cal, electronic, and chemical properties [1–4]. The unique optical property is due to the localized surface plasmon resonance (LSPR) of the gold nanoparticles, which is a collective oscillation of the free electron gas confined in a nanoscale volume. The LSPR provides a remarkable enhancement in the evanescent electromagnetic field at the surface of the nanoparticles, which have found important applications in surface enhanced Raman spectroscopy [5, 6] and LSPR sensing [7–12].
By patterning the gold nanoparticles into a periodic array, additional effects arise due to the interaction of the gold nanoparticles with the photonic crystal (PC) lattice [13]. Such an interaction can result in unique optical properties useful for ma- nipulating light at the nanoscale and leads to strong local field enhancements. Meier et al. have theoretically studied the dipolar interactions of periodic arrays of nanopar- ticles, and predicted the array effects on the plasmon peak and the radiative damping [14]. Lamprecht et al. [15] first experimentally demonstrated the significant varia- tions in the plasmon resonances of these periodic structures with lattice constants due to the in-phase superposition of scattered light. Linden et al. [16, 17] experi- mentally presented the selective suppression of the extinction of a periodic array of
1. A version of this chapter is in preparation for publication. H. Jiang, T. Manifar, A. Bakhtazad, H. Hojjati, J. Sabarinathan and S. Mittler, ’Periodic array of gold nanodisks coupled with evanescent spectroscopy’.
75 gold particles on an indium tin oxide waveguide. The sharp grating-induced plasmon mode of the periodic array of metal nanoparticles has been studied theoretically and experimentally [18–21].
Waveguide evanescent spectroscopy is based on the concept of exciting the micro/nano-objects using the evanescent field of the waveguide and collecting the transmitted light [22]. Combining the gold nanoparticles with a waveguide can couple the LSPR with the evanescent field, providing interesting nano-optical phenomenon, such as enhanced cross-talk [23, 24]. The biosensing approach based on gold nanopar- ticles immobilized on the surface of waveguide has been studied [25, 26]. In previous work, we have theoretically studied the gold-nanoparticle-based photonic crystal on top of a slab waveguide for sensing applications [26].
In this study, light is propagating as a TE0 or TM0 waveguide mode in a channel waveguide. The fabricated waveguide channel is tapered to a 100 µm width in the region overlapping with the gold nanoparticle arrays. Therefore, the waveguide beneath the gold nanoparticle arrays can be approximated as a slab waveguide. The pattern of the chosen gold nanodisks is a square lattice 2-D periodic array as depicted schematically in Figure 4.1. The LSPR is probed by the evanescent field of the waveguide mode. The unique property of this configuration is that the wave-vector of the light is in the same plane as the periodicities, which is the frequently used configuration in studying the 2-D dielectric photonic crystal structures [13]. We have chosen ion-exchanged glass waveguides as the substrate [27, 28], but this approach can be easily translated to other types of waveguides, especially to step index waveguides fabricated out of polymers or inorganic dielectrics.