Direct beam hazard analysis of large beam diameters for laser power beaming

The mission lifetime for unmanned aerial vehicles and unmanned ground vehicles (UGVs) might potentially be increased by transmitting electrical power wirelessly, using a laser source and a photovoltaic array receiver, but such laser power beaming (LPB) requires lasers that present potentially serious dangers to the operators of LPB systems. The analysis in this paper seeks to optimize the wavelength range and corresponding enlarged beam diameters needed to eliminate or reduce direct beam laser hazards while appropriately powering group 1 unmanned aerial systems such as the DJI Phantom 4 or UGVs such as the iRobot 510 Packbot during their operation. A 125-W infrared laser with continuous wavelengths ranging from 800 nm to greater than 1400 nm, operated under the guidelines of The American Standard for the Safe Use of Lasers, is considered. This analysis concludes that for a wavelength of 1297 nm an eye safe minimum expanded beam diameter is 43 cm and that for wavelengths between 1050 and 1400 nm a skin safe minimum beam diameter is 28 cm.