NTT and Mitsubishi Heavy achieve Power Transmission record

NTT, Inc. (NTT), in collaboration with Mitsubishi Heavy Industries Group (MHI), successfully demonstrated the world’s most efficient optical wireless power transmission under atmospheric interference, receiving 152 W of electric power over 1 km for an efficiency rate of 15%. The result advances the companies’ development of technologies to accurately deliver power over long distances where cables cannot be installed or used, such as in disaster-stricken areas or for space-based power systems.
The research was published in August in the scientific journal Electronics Letters, entitled “Demonstration of 15% Efficient Optical Wireless Power Transmission Over 1 km With Atmospheric Turbulence.”

Wireless Power Transmission: Microwaves vs. Laser Beams

Two primary methods of wireless power transmission exist today, with most common practical deployments utilizing microwaves. However, transmission technologies using microwaves face limitations in range, cost, efficiency and efficacy when transmission occurs in real-world conditions under atmospheric interference like heat and wind.

Due to their strong directionality, optical transmission technologies that use laser beams present a solution to this problem. However, the practical application of these optics-based technologies is limited due to the inefficiency of converting laser beams to electric power (via photoelectric conversion) over long distances, a problem compounded by atmospheric interference. Improving photoelectric conversion efficiency requires improving the intensity distribution of the laser beam during long-distance propagation.

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Achieving a Wireless Optical Power Transmission World Record

To achieve this improved uniformity of beam intensity, NTT utilized beam-shaping technology that combined an axicon lens and a concave lens, resulting in a flatter laser beam. The flatter laser beam was then propagated through an atmospheric interference-diffusing beam homogenizer and directed at a light-receiving panel, which was augmented with bypass capacitors to further suppress fluctuations in output current caused by atmospheric interference. NTT designed and implemented the experiment’s transmission optics (e.g., beam shaping technologies) while MHI designed and implemented the experiment’s photodetector optics (e.g., photodetector panels, homogenizers and capacitors).

In January and February 2025, NTT そして 三菱重工 scientists conducted an optical wireless power transmission experiment on the runway at the Nanki-Shirahama Airport in Shirahama Town, Nishimuro District, Wakayama Prefecture. A transmission booth equipped with an optical system for emitting laser beams was installed at one end of the runway, and a reception booth containing a light-receiving panel was placed 1 kilometer away.

During transmission, the optical axis of the laser was set at a low height of approximately 1 m above the ground and aligned horizontally. As a result, the beam was strongly affected by ground heating and wind, and the experiment was conducted under conditions with particularly strong atmospheric turbulence.

The experiment resulted in an average electrical power extraction from the receiving panel of 152 W, corresponding to a wireless power transmission efficiency of 15% (defined as the ratio of received power to transmitted power). Furthermore, continuous power delivery was successfully maintained for 30 minutes, confirming the feasibility of long-duration power transmission using this technology.

This result marks the world’s highest optical wireless power transmission efficiency ever demonstrated using a silicon-based photoelectric conversion element under conditions of strong atmospheric interference.

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