Conducted on the runway at Nanki-Shirahama Airport in Wakayama, Japan, the companies claim to have successfully transmitted 152 MW of electric power over one kilometre with 15% efficiency. Findings were first published in Electronics Letters in August 2025.

Current wireless power transmission technologies primarily use microwave-based systems. While practical, these methods are constrained by challenges in range, cost, efficiency and reliability.

In contrast, optical transmission using laser beams offers stronger directionality and the potential for higher efficiency. However, the conversion of laser beams into electricity over long distances is notoriously inefficient – when the long-distance laser beam propagates, especially in the atmosphere, the intensity distribution becomes uneven, and the efficiency of converting laser light into electric power becomes low.

Combining NTT’s beam shaping technology with MHI’s light receiving technology, a laser beam with an optical power of 1,035 Watts was generated and transmitted at a height of about one metre above ground level – a position chosen to deliberately expose the system to the strongest atmospheric interference. NTT deployed a diffractive optical element to reshape the beam into a flat, uniform profile designed to hold its intensity over the full one-kilometre distance.

At the receiving station, MHI installed a panel equipped with a homogeniser to smooth out fluctuations in the beam and circuits to stabilise the output current. Together, these technologies overcame the ‘hot spots’ normally caused by turbulence. Despite challenging test conditions, the system achieved stable power delivery of 152 Watts for a continuous 30-minute period.

The result corresponds to a wireless transmission efficiency of 15% – thought to be the highest ever recorded for silicon-based photoelectric conversion under atmospheric interference.

Even higher power transfer efficiency can be expected, the companies claim, by employing photovoltaic devices specifically designed to match the wavelength of the laser light. In addition, the use of laser light sources with higher output power would make it possible to supply larger amounts of electricity.  

As a result, flexible and rapid power delivery could be achieved in remote areas such as disaster-stricken regions and remote islands, where the installation of power cables has traditionally been difficult.  

In addition, potential applications in space are anticipated, including power delivery to mobile platforms. Looking further ahead, the technology could be applied to power space data centres and lunar rovers, as well as to space solar power systems in which electricity is transmitted from geostationary satellites to the ground via laser.

Figure 1: Schematic diagram of experimental system
NTT/MHI