Deep-Subwavelength CMOS Hybrid Plasmonic Waveguide

Valentyn S. Volkov Department of Technology and Innovation, University of Southern Denmark, Odence, Denmark Laboratory of Nanooptics and Plasmonics, Mocsow Institute of Physics and Technology, Dolgoprudny, Russia Dmitry Yakubovsky Laboratory of Nanooptics and Plasmonics, Mocsow Institute of Physics and Technology, Dolgoprudny, Russia Roman Kirtaev Laboratory of Nanooptics and Plasmonics, Mocsow Institute of Physics and Technology, Dolgoprudny, Russia Dmitry Fedyanin Laboratory of Nanooptics and Plasmonics, Mocsow Institute of Physics and Technology, Dolgoprudny, Russia

Surface plasmon polaritons (SPPs) have been regarded as the key to break down the fundamental diffraction limit in conventional photonics systems, as they offer the unique potential to guide and route light at the truly nometer scale [1]. In the past years, a variety of deep-subwavelength plasmonic structures have been proposed and investigated, including dielectric-loaded SPP waveguides [2], V-groove waveguides [3] and metal nanowires [4]. One of the most distinguished works among them is the recent demonstration of hybrid plasmonic structures that naturally integrate high-index semiconductor materials and metal waveguides, hence successfully overcoming the conventional constraints imposed by traditional guiding mechanisms in previously studied SPP waveguides, i.e. the fundamental trade-off between mode confinement and propagation loss [5]. However, for practical implementation, such waveguides must be integrated on a silicon chip and be fabricated using a standard CMOS fabrication process, which is not really achievable with ’’traditional’’ plasmonic metals (gold and silver).

In this work, we present hybrid plasmonic waveguides based on the horizontal Cu(150 nm)-SiO₂(10nm)-Si₃N₄(400nm×400nm) structure fabricated with a CMOS-compatible process (Fig. 1), and characterize it at telecommunication wavelengths by use of the scanning near-field optical microscope (SNOM). Using SNOM imaging and end-fire coupling with a tapered fiber connected to a tunable laser at telecommunication wavelengths (1450–1580 nm), we demonstrate efficient and strongly-confined subwavelength SPP mode guiding at moderate propagation losses and investigate optical properties of the proposed waveguide structure. These results may facilitate the application of the present structure in high-density photonic integration.

Figure 1. SEM image of the fabricated plasmonic waveguide integrated with the funnel structure.

[1] W. L. Barnes, A. Dereux, and T. W. Ebbesen, Nature 424, 824(2003).

[2] T. Holmgaard and S. Bozhevolnyi, Phys. Rev. B 75(24), 245405 (2007).

[3] V. S. Volkov et al., Nano Lett. 7(4), 880 (2007).

[4] E. Verhagen et al., Phys. Rev. Lett. 102(20), 203904 (2009).

[5] V. J. Sorger et al., Nat. Comm. 2, 331(2011).

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