Friedrich-Alexander-Universität Erlangen-Nürnberg

Optical circuitry, antennas, directional couplers and discrete diffraction with surface plasmon polaritons

Optical circuitry, antennas, directional couplers and discrete diffraction with surface plasmon polaritons

Subwavelength SPP waveguides for optical nanocircuitry

Subwavelength, plasmonic waveguides open the way to the manipulation of light in photonic circuits at the nanoscale. Surface Plasmon Polaritons (SPP) allow for focusing light to scales below the Abbe diffraction limit. Highly integrated waveguiding becomes possible, whereas the diffraction limit in classical waveguides inhibits integration in the size scales of current CPU generations (down to ~50 nm). Compared with competing techniques as dielectric waveguides, plasmonic slab waveguides or dielectric loaded SPP waveguides, gap SPP waveguides allow for the strongest field confinement, achieving real subwavelength operation. At the same time, in gap SPP waveguides, compared to alternative SPP waveguide geometries, losses are reduced though still higher than in waveguides with lower confinement. Existing and new waveguide geometries are first simulated with Finite Elements Method (FEM) calculations. In the second step we fabricate such waveguides with Focused Ion Beam (FIB) milling into thin metal films and finally investigate them with near field (Near Field Scanning Optical Microscope, NSOM) and far field technologies. 

Figure 1 Fundamental mode of a plasmonic gap waveguide: Electric field. FEM calculation. (c) Arian Kriesch

Directional couplers and discrete diffraction

Directional couplers, connecting different transmission lines, are fundamental building blocks in macroscopic fiber optics and in the microwave domain. Transferring this concept into the nanoworld is a promising challenge as it allows for transferring light from one subwavelength waveguide to the other. Coupling in the size of a wavelength has recently been realized in dielectric waveguides. We successfully fabricate subwavelength SPP waveguides with pitch around 120 nm. Combined with loaded optical antennas and near field as well as far field measurement techniques, those allow for the detailed investigation of small scale coupling and serve as a component for discrete diffraction in larger waveguide arrays.

Collaboration with Arian Kriesch, Ulf Peschel, Daniel Ploss, Jing Wen, IOIP Uni Erlangen / MPL and Stanley Burgos, Harry A. Atwater, Thomas J. Watson Labroratory of Applied Physics, California Institute of Technology



Figure 2 (a) Nanocircuitry compound, forming a subwavelength directional SPP coupler. (b)Coupling is visible in the right emission spot. (c) Arian Kriesch


  1. Wen, J., Banzer, P., Kriesch, A., Ploss, D., Schmauss, B., & Peschel, U. (2011). Experimental cross-polarization detection of coupling far-field light to highly confined plasmonic gap modes via nanoantennas. Applied Physics Letters, 98(10), 101109. AIP. doi:10.1063/1.3564904
  2. Wen, J., Romanov, S., & Peschel, U. (2009). Excitation of plasmonic gap waveguides by nanoantennas. Optics Express, 17(8), 5925. OSA. doi:10.1364/OE.17.005925
  3. Kriesch, A., Ploss, D., Wen, J., Banzer, P., & Peschel, U. (2011). Probing nanoplasmonic waveguides and couplers with optical antennas. CLEO/Europe and EQEC 2011 Conference Digest. Optical Society of America. Retrieved from
  4. Wen, J., Banzer, P., Ploss, D., Kriesch, A., Schmauss, B., & Peschel, U. (2010). Excitation of Gap Plasmonic Waveguides by Nano Antennas. Quantum Electronics and Laser Science Conference. Optical Society of America. Retrieved from







SAOT provides an interdisciplinary research and education program of excellence within a broad international network of distinguished experts to promote innovation and leadership in the areas

Optical Metrology
Optical Material Processing
Optics in Medicine
Optics in Communication and Information Technology
Optical Materials and Systems
and Computational Optics.