Advances in laser and photovoltaic converter technologies may allow high-power wireless recharging of platforms and sensors at extended ranges. These remote platforms may include flying, land-based, or submerged vehicles, satellites, and sensors at hazardous locations. Commercially available fiber lasers have proven to be an enabling technology in a variety of industrial applications such as cutting, welding, and annealing. These lasers also are having a positive effect in many defense programs—for instance, the Navy’s laser weapon system has recently deployed aboard USS Ponce (AFSB[I] 15) for at-sea testing. In addition, commercially available photovoltaic converters have advanced to a point where high conversion efficiency from laser energy to electrical energy is now possible.
In the 1890s, Nikola Tesla performed some of the first experiments demonstrating wireless recharging—sometimes called power beaming—using high-frequency electromagnetic radiation. Microwaves have been used since in short-range wireless recharging experiments because of their high power-conversion efficiency. For long-range recharging, however, large transmission and receiving antennae are required because of the longer wavelengths associated with microwave radiation. Practical long-range recharging only can be achieved using the significantly shorter wavelengths associated with laser beams. The use of lasers can significantly reduce the size and weight of the transmitting and receiving platforms.
Research groups at the National Aeronautics and Space Administration, Kinki University in Japan, LaserMotive Inc., and the Naval Research Laboratory have experimented with wireless recharging using a variety of platforms such as rovers, kite planes, helicopters, and climbers using solid-state lasers and photovoltaic converters. One configuration for remote wireless recharging of an unmanned aerial vehicle (UAV) involves using a high-power, continuous wave fiber laser and beam director. Disturbances in the atmosphere (i.e., turbulence and aerosols) will affect the laser’s power propagation and delivery to the platform and may require adaptive optics for correction.