Agent swarms: Cooperation and coordination under stringent communications constraint.

Here we consider the communications tactics appropriate for a group of agents that need to "swarm" together in a challenging communications environment. Swarms are increasingly important in a number of applications, including land, air, sea and space exploration, and their constituent agents could be satellites, drones, or other autonomous vehicles. A particularly difficult problem is to autonomously connect a swarm of agents together in a situation where stringent communication constraints are present, whether due to a need for stealth, restricted on-board power, external requirements to avoid certain broadcast directions, or equipment & hardware limitations.

Customizing longitudinal electric field profiles using spatial dispersion in dielectric wire arrays.

We show how spatial dispersion can be used as a mechanism to customize the longitudinal profiles of electric fields inside modulated wire media, using a fast and remarkably accurate 1D inhomogeneous model. This customization gives fine control of the sub-wavelength behaviour of the field, as has been achieved recently for transverse fields in simpler slotted-slab media. Our scheme avoids any necessity to run a long series of computationally intensive 3D simulations of specific structures, in order to iteratively converge (or brute-force search) to an empirical 'best-performance' design according to an abstract figure-of-merit.

Comment on "Correct definition of the Poynting vector in electrically and magnetically polarizable medium reveals that negative refraction is impossible.".

Physically valid electromagnetic continuity equations can be generated from either the usual form of the Poynting vector E x H or the alternative E x B form. However, the continuity equations are not identical, which means that quantities following from E x H cannot always be compared directly to those from E x B. In particular, the work done on the bound current densities are attributed differently in the two representations.

Harmonic extended supercontinuum generation and carrier envelope phase dependent spectral broadening in silica nanowires.

Numerical simulations are used to study the interaction dynamics between pump spectral broadening and third harmonic generation during supercontinuum generation in a highly nonlinear fused silica nanowire using sub-100 fs pump pulses. In particular, we show that the superposition of the generated third harmonic with the spectrally-broadened pump pulse exhibits significant dependence on the input pump carrier envelope phase, and we examine this dependence as a function of pulse duration and propagation distance.

Ultrashort-pulse modulation in adiabatically prepared Raman media.

We demonstrate the efficient modulation of an approximately 100-femtosecond pulse in a Raman medium coherently prepared by nanosecond pulses. Raman sidebands of the ultrashort pulse spanning 360 THz are generated with an efficiency of >5%. We show that the mechanism permitting the sidebands to be generated is the preparation of a significant vibrational coherence in the medium that is robust to disturbance by an intense short pulse.