(407b) UV Surface Plasmon Resonance Modification By Graphene Pi Plasmon Resonance

UV surface plasmon resonance modification by

Graphene Pi plasmon resonance

Xueling Cheng¹, Sourangsu Banerji¹, Jieying Mao²,
Sara Arezoomandan¹, Ting Zhang², Steve Blair¹ Berardi
Sensale-Rodriguez¹ and Yunshan wang³

text-indent:-.25in">1.    
Department of Electrical and Computer
Engineering, University of Utah

text-indent:-.25in">2.    
Department of Physics and
Astronomy, University of Utah

text-indent:-.25in">3.    
Department of Chemical
Engineering, University of Utah

Despite of increasing understandings of UV
plasmonic materials, materials that can enable active tuning of UV plasmonic
resonance has not been reported. Here, we demonstrate modification of UV SPR on
an aluminum (Al) hole-array by coupling Graphene π plasmon resonance with Al SPR.
Graphene monolayer exhibits an abnormal
absorption peak in the UV region (270-290nm) due to π
plasmon resonance. The location and intensity of the absorption peak depends on
the position of Fermi-level, which can be adjusted by electric or chemical
doping. Al SPR is shown here to be modified by coupling Graphene π plasmon
resonance with Al SPR.

FDTD simulation shows modification of Al
hole-array transmission by adding a single layer of Graphene on top. The shifts
of transmission dips after adding a Graphene layer shows a distinct transition
at around the Graphene π plasmon position. For transmission dips that are located
at shorter wavelength compared to Graphene π
plasmon, up to 8nm blue shifts occur after adding Graphene. On the other hand, up
to 20nm red shifts occur for transmission dips that are at longer wavelength
relative to Graphene π plasmon(fig.1). This
change in the sign of shifts of transmission dips in Figure.2 corresponds to the
change in the sign of the real permittivity of Graphene (fig.3). The amount of
shifts diminishes as the transmission dip moves further away from Graphene π
plasmon resonance into the visible spectrum. Experimentally we have observed
redshifts of SPR dips but not blue shifts possibly due to poor light collection
below 250nm. Besides, FDTD
simulations shows enhanced near-field intensity after coupling Graphene with Al
hole array. The observed tunability and the enhanced local electric fields can
find applications in tunable UV LED, label free biosensors, etc.

Figure 1. Al hole array with or without graphene for hole
array period equals to 200nm (left) and 280 nm (right)

Figure 2. Wavelength
shift after loading graphene Figure 3. Permittivity
of graphene

Figure 4. For
hole array period equals to 280 nm, FDTD shows the near field intensity of the
device without graphene (a) top surface and (b)cross-section, and the near
field intensity of the device with graphene (c) top surface and (d)
cross-section.

font-family:" times new roman> 

font-family:" times new roman>