Dispersive Lossy Media for Narrowing Plasmon Linewidths

Narrow plasmon linewidths are often desirable for plasmonic devices such as biosensors. Loss is often associated with broad linewidths, and much effort is spent in reducing losses in metals. Although losses can be effectively reduced by a variety of methods such as, reducing surface roughness, and including optical gain to counter the loss, losses will never be fully eliminated from a system [1]. Rather than avoiding loss, we focus on how the linewidth can be reduced in the presence of loss. In this paper, we show how a dispersive lossy surrounding dielectric can narrow the plasmon linewidth. We support this claim with experimental scattering measurements using a dark field microscope, as well as with Green function calculations.