You are likely at least slightly aware of the work that famed engineer, scientist, and researcher Nikola Tesla did in the early 1900s in his futile attempt to wirelessly transmit usable power via a 200-foot tower. The project is described extensively on many credible web sites, such as “What became of Nikola Tesla’s wireless dream?” and “Tesla’s Tower at Wardenclyffe” as well as many substantive books.
Since Tesla, there have been numerous other efforts to transmit power without wires using RF (microwave and millimeter waves) and optical wavelengths. Of course, both “bands” are wireless and governed by Maxwell’s equations, but there are very different practical implications.
Proponents of wireless transmitted power see it as a power-delivery source for both stationary and moving targets including drones and larger aircraft—very ambitious objectives, for sure. We are not talking about near-field charging for devices such as smartphones, nor the “trick” of wireless lighting of a fluorescent bulb that is positioned a few feet away from a desktop Tesla coil. We are talking about substantial distances and power.
Most early efforts to beam power were confined to microwave frequencies due to available technologies. However, they require relatively larger antennas to focus the transmitted beam, so millimeter waves or optical links are likely to work better.
The latest efforts and progress have been in the optical spectrum. These systems use a fiber-optic-based laser for a tightly confined beam. The “receivers” for optical power transmission are specialized photovoltaic cells optimized to convert a very narrow wavelength of light into electric power with very high efficiency. The reported efficiencies can exceed 70%, more than double that of a typical broader-spectrum solar cell.
In one design from Powerlight Technologies, the beam is contained within a virtual enclosure that senses an object impinging on it—such as a person, bird, or even airborne debris—and triggers the equipment to cut power to the main beam before any damage is done (Figure 1). The system monitors the volume the beam occupies, along with its immediate surroundings, allowing the power link to automatically reestablish itself when the path is once again clear.
Figure 1 This free-space optical-power path link includes a safety “curtain” which cuts off the beam within a millisecond if there is a path interruption. Source: Powerlight Technologies
Although this is nominally listed as a “power” project, as with any power-related technology, there’s a significant amount of analog-focused circuitry and components involved. These provide raw DC power to the laser driver and to the optical-conversion circuits, lasers, overall system management at both ends, and more.
Recent progress raises effectiveness
In May 2025, DARPA’s Persistent Optical Wireless Energy Relay (POWER) program achieved several new records for transmitting power over distance in a series of tests in New Mexico. The team’s POWER Receiver Array Demo (PRAD) recorded more than 800 watts of power delivered during a 30-second transmission from a laser 8.6 kilometers (5.3 miles) away. Over the course of the test campaign, more than a megajoule of energy was transferred.
In the never-ending power-versus-distance challenge, the previous greatest reported distance records for an appreciable amount of optical power (>1 microwatt) were 230 watts of average power at 1.7 kilometers for 25 seconds and a lesser (but undisclosed) amount of power at 3.7 kilometers (Figure 2).
Figure 2 The POWER Receiver Array Demo (PRAD) set the records for power and distance for optical power beaming; the graphic shows how it compares to previous notable efforts. Source: DARPA
To achieve the power and distance record, the power receiver array used a new receiver technology designed by Teravec Technologies with a compact aperture for the laser beam to shine. That’s to ensure that very little light escapes once it has entered the receiver. Inside the receiver, the laser strikes a parabolic mirror that reflects the beam onto dozens of photovoltaic cells to convert the energy back to usable power (Figure 3).
Figure 3 In the optical power-beaming receiver designed for PRAD, the laser enters the center aperture, strikes a parabolic mirror, and reflects onto dozens of photovoltaic cells (left) arranged around the inside of the device to convert the energy back to usable power (right). Source: Teravec Technologies
While it may seem logical to use a mirror or lens when it comes to redirecting laser beams, the project team instead found that diffractive optics were a better choice because they are good at efficiently handling monochromatic wavelengths of light. They used additive manufacturing to create optics and included an integrated cooling system.
Further details on this project are hard to come by, but that’s almost beside the point. The key message is that there has been significant progress. As is usually the case, some of it leverages progress in other disciplines, and much of it is “home made.” Nonetheless, there are significant technical costs, efficiency burdens, and limitations due to atmospheric density—especially at lower attitudes and ground level.
Do you think advances in various wireless-transmission components and technologies will reach to where it’s a viable power-delivery approach for broader uses besides highly specialized ones? Can it be made to work for moving targets as well as stationary ones? Or will this be one of those technologies where success is always “just around the corner”? And finally, is there any relationship between this project and the work on directed laser energy systems to “shoot” drones out of the sky, which has parallels to the beam generation/emission part?
Bill Schweber is a degreed senior EE who has written three textbooks, hundreds of technical articles, opinion columns, and product features. Prior to becoming an author and editor, he spent his entire hands-on career on the analog side by working on power supplies, sensors, signal conditioning, and wired and wireless communication links. His work experience includes many years at Analog Devices in applications and marketing.
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