Dispersing Light with Surface Plasmon Polaritonic Crystals

Spectral dispersion of light on a finite-size surface plasmon polaritonic (SPP) crystal has been studied. The angular wavelength separation of one or more orders of magnitude higher than in other state-of-the-art wavelength-splitting devices available to date has been demonstrated. The two-stage process is responsible for the dispersion value, which involves conversion of the incident light into SPP Bloch modes of a nanostructure followed by the SPP Bloch waves refraction at the SPP crystal boundary. The high spectral dispersion achievable in plasmonic devices may be useful for integrated high-resolution spectroscopy in nanophotonic, optical communication and lab-on-a-chip applications.

Figure 1

(a) Electron microscope image of the SPP crystal used in the experiments; (b) Principle of the SPPC induced dispersion showing a finite-size SPPC, a set of scatterers used for SPP visualization, and illumination conditions; (c) Experimental setup: TLS—tunable laser source; WLS—white light source (unpolarized); PM—power meter; OSA—optical spectrum analyzer; PAN—polarization analyzer; IRC—infrared camera; (d) Schematics of the band structure of the SPP crystal in the vicinity of $\Gamma$ point of the Brillouin zone; the circle indicates the states accessible with normally incident Gaussian laser beam; (e) The experimentally measured SPP dispersion of the crystal shown in (a) in the range of wavelengths used in the following experiments.

Figure 2

Series of images of the intensity distributions over the metal surface for the different polarizations of the incident light as indicated by the arrows. The illuminating light wavelength is $\lambda =1523\mathrm{nm}$.

Figure 3

Series of images of the intensity distributions over the metal surface for the different wavelengths and polarizations of the incident light: (a), (c) $\lambda =1524.4\mathrm{nm}$, (b), (d) $\lambda =1524.8\mathrm{nm}$, (e) $\lambda =1552.0\mathrm{nm}$ (incident light polarization is indicated by arrows); (f) unpolarized white light. Some of the representative scatterers are indicated by the squares D on the images.

Figure 4

(a) The wavelength dependencies of the intensity averaged over the scatterers D1 and D2 marked on the images in Fig. 3 for vertical (circles) and horizontal (squares) polarizations of the incident light as indicated in Fig. 3. (b) Cross sections along the four scatterers between the scatterers D1 and D2 for different wavelengths of the incident light. Please note that due to nonlinearity of the imaging camera response, the contrast may be suppressed on the presented plots.