Drone swarms that have deluged Ukraine for years — and crossed the border into Poland last week — have sent NATO militaries in Europe rushing to upgrade air defenses in case they ever face a similar threat.

Soon they will have a new solution: lasers.

Scientists have for decades sought to harness directed energy beams into weapon systems that would be cheaper and more efficient than missiles or rockets. A growing number of countries are developing or deploying their own laser air defenses, and some have already been used in war, by Israel and Ukraine.

A NATO nation in Europe is now buying an air defense laser from an Australian company, which officials, experts and industry executives said appears to be the highest-power direct energy system to be sold on the global weapons market. That is a sign that they are becoming more widely available and could be a mainstay for future warfare.

The Australian laser’s maker, Electro Optic Systems, advertises it as able to shoot down 20 drones a minute, at a cost of less than 10 cents per shot. Nicknamed “Apollo” for the Greek god of light, it has about the same level of power as Israel’s highly anticipated Iron Beam air defense laser, which is being built for its own military.

“The Ukrainian war and the Gaza war were key trigger events that everybody thought, ‘It’s the time now to make this operational. We should not spend any more years in doing demonstrations, tests and prototyping,’” Andreas Schwer, Electro Optic Systems’ chief executive, said in a recent interview.

“We have some clients which are so much under actual threat that they say, ‘Listen, we can’t wait — we need something tomorrow,’” Mr. Schwer added. He declined to say which NATO nation is buying the laser.