Design and Characterization of Dielectric-Loaded Plasmonic Directional Couplers

Abstract

Abstract-Ultracompact directional couplers (DCs) based on dielectric-loaded surface plasmon-polariton waveguides (DLSPPWs) are analyzed using the effective index method (EIM), with the coupling, both in the parallel interaction region and inand out-coupling regions, being taken into account. Near-field characterization of fabricated DCs performed with a scanning near-field optical microscope verifies the applicability of the EIM in the analysis and design of DLSPPW-based wavelength-selective DCs. The design approach applicable to a large variety of integrated optical waveguides is developed, enabling the realization of DCs in which optical signals at two different wavelengths are coupled into two separate output channels. The developed approach ensures minimization of the crosstalk and overall DC length via simultaneous adjustment of the waveguide separation and length of the interaction region. As an example, the design of a DLSPPW-based DC for complete separation of telecommunication signals at the wavelengths = 1400 nm and = 1600 nm between two output channels separated by 6 m is worked out, resulting in the total device length of 52.3 m. In addition, the design of an ultracompact DLSPPW-based DC waveguide crossing that ensures a very low crosstalk over a large wavelength band in the telecommunication range is considered.

Active Nanophotonic Circuitry Based on Dielectric‐loaded Plasmonic Waveguides

“…Clear beating of the DLSPPW mode between coupled waveguides was experimentally observed using the leakage radiation microscopy ( Figure 5 b). [ 110,111 ] The strength of coupling between the waveguides is represented by a coupling length L c , the distance along the waveguide at which the energy of the propagating mode is fully transferred to the neighboring one. The increase of the coupling length with the distance between the waveguides has an exponential dependence ( Figure 5 c).…”

“…The length of the waveguides can be chosen so at a given wavelength after few oscillations between the waveguides, the mode can be fully localized in one of them, while for mode at another wavelength, having longer (or shorter) coupling length, the number of oscillations may be such that the mode will be fully localized in another waveguide. Directional couplers, comprising input and output S-bends have been realised [ 138,111 ] (Figure 14 ). As predicted by the theory (Section 2), the coupling length L c was found to have a strong dependence on the separation distance (cf.…”

Liquid crystal-based dielectric loaded surface plasmon polariton optical switches

“…Among these, the dielectric loaded surface plasmon polariton (DLSPP) waveguide offers some distinctive advantages 4 and has been employed in numerous passive wavelength-selective optical components. [5][6][7][8][9] In particular, DLSPP waveguides are capable of providing strong confinement in both transverse directions and permit the design of low-loss bend elements, while keeping overall propagation losses relatively low. Moreover, by thermally tuning the refractive index of the dielectric material used as loading, active components can be implemented.…”

Nonlinear switching in tapered plasmonic couplers

“…One of the key elements of integrated photonic circuits, a directional coupler, is based on cross-talk coupling between two neighboring waveguides. Such directional couplers for plasmonic waves have been studied theoretically and even demonstrated experimentally for different geometries [5]- [7]. Directional couplers have been also suggested for converting the modes of an optical dielectric waveguide into plasmonic modes propagating along a thin metal stripe [8].…”