Abstract: In accordance with various embodiments of the disclosed subject matter, a system, apparatus and method is configured to receive/process radio frequency emanations of a potentially threatening drone to generate therefrom a human-recognizable audio signal characteristic of the drone (i.e., a “voice” of the drone) so that a warfighter may be alerted to the activity of the drone and respond accordingly.

Abstract: An novel fiber pump signal combiner is disclosed in which a fiber bundle array is coupled to a double-clad fiber with a taper section that is formed by etching a tapered outer surface into the cladding of a fiber rod to produce a high quality tapered outer surface free of defects with an inner core that has a constant diameter.

Abstract: An improved method and apparatus for passively conjugating the phases of a distorted wavefronts resulting from optical phase mismatch between elements of a fiber laser array are disclosed. A method for passively conjugating a distorted wavefront comprises the steps of: multiplexing a plurality of probe fibers and a bundle pump fiber in a fiber bundle array; passing the multiplexed output from the fiber bundle array through a collimating lens and into one portion of a non-linear medium; passing the output from a pump collection fiber through a focusing lens and into another portion of the non-linear medium so that the output from the pump collection fiber mixes with the multiplexed output from the fiber bundle; adjusting one or more degrees of freedom of one or more of the fiber bundle array, the collimating lens, the focusing lens, the non-linear medium, or the pump collection fiber to produce a standing wave in the non-linear medium.

Abstract: Single transverse mode fiber amplifier and laser operation is obtained with a multi-mode signal core surrounded by cladding containing irregular microstructuring that causes loss in all of the core modes except the fundamental while maintaining robust guiding of the fundamental mode resulting in higher fiber laser power capacity.

Abstract: A modified photonic crystal fiber yielding a higher peak power for a given maximum intensity. The multi-mode signal core has a depressed index of refraction that pushes the mode distribution to the core edges while a pattern of larger air holes is used to flatten the mode distribution. The core is further surrounded by tuned cladding elements defined by a pattern of smaller air holes that cause loss in all of the core modes except the fundamental while maintaining robust guiding of the fundamental mode.