We present an iterative design method for the coupling and the mode conversion of arbitrary modes to focused surface plasmons using a large array of aperiodically randomly located slits in a thin metal lm. As the distance between the slits is small and the number of slits is large, significant mutual coupling occurs between the slits which makes an accurate computation of the field scattered by the slits difficult. We use an accurate modal source radiator model to efficiently compute the fields in a significantly shorter time compared with three-dimensional (3D) full-field rigorous simulations, so that iterative optimization is efficiently achieved. Since our model accounts for mutual coupling between the slits, the scattering by the slits of both the source wave and the focused surface plasmon can be incorporated in the optimization scheme. We apply this method to the design of various types of couplers for arbitrary fiber modes and a mode demultiplexer that focuses three orthogonal fiber modes to three different foci. Finally, we validate our design results using fully vectorial 3D nite-difference time-domain (FDTD) simulations.
The energy consumption per transmitted bit is becoming a crucial figure of merit for communication channels. In this paper, we study the design trade-offs in photodetectors, utilizing the energy per bit as a benchmark. We propose a generic model for a photodetector that takes optical and electrical properties into account. Using our formalism, we show how the parasitic capacitance of photodetectors can drastically alter the parameter values that lead to the optimal design. Given certain energy-per-bit and bandwidth requirements, is it possible that a photodetector optimized for the energy per bit would be noise limited? We identify different noise sources and model them in the simplest useful approximation in order to calculate this noise limit. Finally, we apply our theory to a practical case study for an integrated plasmonic photodetector, showing that energies per bit below 100 attojoules are feasible despite metallic losses and within noise limitations without the introduction of an optical cavity or voltage amplifying receiver circuits.
Numerical calculations with nite-dierence time-domain (FDTD) on metallic nanostructures in a broad optical
spectrum require an accurate approximation of the permittivity of dispersive materials. In this paper, we present
the algorithms behind B-CALM (Belgium-California Light Machine), an open-source 3D-FDTD solver operating
on Graphical Processing Units (GPUs) with multi-pole dispersion models. Our modied architecture shows a
reduction in computing times for multi-pole dispersion models. We benchmark B-CALM by computing the
absorption eciency of a metallic nanosphere on a broad spectral range with a six-poles Drude-Lorentz model
and compare it with Mie theory.
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