High Efficiency kW-class 1550 nm Steerable Diffraction-Limited Laser Diode Arrays for Energy Web Dominance

DARPA and the US Department of Defense are interested in technologies which can enable a wireless energy web comprising multiple nodes to enhance military capabilities.  Wireless power transmission is difficult to scale to relevant powers and distances due to poor system efficiency.  For example, as transmission distances increase there is a severe reduction in system efficiency; at distances of ~1000 m, the current state-of-the-art efficiency is limited to just ~1%.  Optical power beaming is an excellent candidate for addressing this technology gap; however, specific challenges facing this technology include eye safety, the conversion efficiency of the transmitter, efficient transmission over long distances, and atmospheric aberrations.  Nearly diffraction-limited high power lasers operating around 1550 nm are required to overcome these challenges, however such lasers are inherently inefficient due to the cascaded diode-pumped fiber or solid-state laser brightness conversion process.  It would be ideal if suitably bright, efficient, and powerful diode lasers could be used directly, thus eliminating the low efficiency brightness conversion process and enabling high (~50%) efficiency.  We propose the development of extremely high efficiency semiconductor lasers which are directly suitable for power beaming without the need for inefficient brightness conversion.  Our highly disruptive approach seeks to demonstrate a phase-locked diffraction-limited direct diode laser array with total output power >1 kW (scalable to >50 kW) and wall-plug efficiency >50% at an emission wavelength of 1550 nm.