Modeling a femtosecond filament array waveguide for guiding pulsed infrared laser radiation

A hollow cylindrical plasma waveguide, which cladding consists of a large number of a chaotically distributed plasma filaments induced by the propagation of femtosecond (fs) laser pulses in air, is shown to support guided modes of pulsed infrared (IR) laser radiation. Taking into account the discontinuity and the finiteness of the waveguide cladding, the loss coefficient loss of the laser radiation is calculated for different spatial configurations. We report how the waveguide loss depends on its structural parameters like normalized plasma diameter, distance between filaments, core-radius, cladding's thickness, and filaments' electron density. For typical plasma parameters, the loss of the fs plasma waveguide is found to be lower than that of freely propagating IR laser beams to distances in the order of the filamentation length. This fact allows the delivery of collimated pulsed laser light over long distances in atmospheric air, which is necessary for optical-based remote sensing and the detection of chemical and biological agents.