Subwavelength Line Imaging Using Plasmonic Waveguides

We investigate the subwavelength imaging capacity of a 2-D fanned-out plasmonic waveguide array, formed by air channels surrounded by gold metal layers for operation at near-infrared wavelengths, via finite-element simulations. High resolution is achieved on one side of the device by tapering down the channel width, while simultaneously maintaining propagation losses of a few decibels. On the other, low-resolution, side output couplers are designed to optimize coupling to free space and to minimize channel cross talk via surface plasmons. Point sources separated by λ/15 can still be clearly distinguished. Moreover, up to 90% of the power of a point dipole is coupled to the device. Applications are high-resolution linear detector arrays and, by operating the device in reverse, high-resolution optical writing.