Surface plasmon polariton cavities

Surface plasmon polaritons (SPPs), electromagnetic surface waves propagating along metal-dielectric interface with an evanescently decaying electric field intensity into the neighboring media, show unique physical properties attracting great interest for applications in fields such as nanophotonics, spectroscopy, lithography, imaging and biosensing. Selective loading of metal or a dielectric thin film on a plasmonic surface forms a plasmonic cavity which provides a lateral confinement along the propagation direction. Localization of electromagnetic field in plasmonic cavities provides opportunities for new applications ranging from cavity quantum electrodynamics to nonlinear optics. Metallic loss, however, limits the quality factor of the plasmonic cavities.

Experimental dispersion curves showing the bandgap and cavity state for 15:0 μm long cavities with grating groove depths of (a) 15 nm, (b) 30 nm, and (c) 50 nm. DFPM images of three cavities with grating groove depths of (d) 15 nm, (e) 30 nm, and (f) 50 nm. DFPM imaging is performed at an incidence angle of ∼42:5°, and the wavelength of the incident light is ∼615 nm. (g) Line profiles perpendicular to the long axis of the cavities indicate the intensity of the scattered SPP waves from the cavity region. FDTD calculated twodimensional electric field distribution at the cavity wavelength for 15:0 μm long three plasmonic cavities with grating groove depth of (h) 15 nm, and (i) 50 nm. As the depth of the grating groove increases, localization of SPPs in the cavities increases as well. The white colored bars indicate a 15:0 μm long distance. The vertical length of the images in (h) and (i) is ∼2 μm long. [PDF]

In this research field we are studying one and two dimensional cavity arrays made from uniform, biharmonic and Moiré surfaces. A high-Q plasmonic cavity can be achieved on metallic Moiré surfaces formed by superimposing two periodic patterns with slightly different periodicities.  Using intercavity coupling as a parameter, we create conditions for traveling and standing wave configurations and observe the conditions for light coupling.  Using arrays of grating cavities, we have shown the first ever slow plasmon propagation. We are currrently studying exciton-plasmon interaction  on plasmonic cavities. Dye and quantum dot based excitons are being studied for improved emission characteristics leading a cavity based plasmonic laser. Large Rabi splittings we recently observed are encouraging steps in this direction.Finally, we plan to study interaction of various light emitting media with such cavities with the aim to constructing a plasmonic laser.

AFM images of Moiré surfaces with a superperiod of (a) 9.0 and (b) 2:5 μm. Line profiles extracted from (c) the AFM image in (a), and (d) the AFM image in (b).

Bilkent University Advanced Research Laboratories