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The Dream of Fusion Energy

Gerd Leuchs

It is remarkable that optics and photonics, like no other field, is paving the way for future technologies.

[Image: S. Spangenberg]

When searching for the most economic, readily available energy source on Earth, independent of time and weather, scientists have looked for reactions that provide the highest amount of energy per elementary process. Nuclear fission was an obvious choice, given the high binding energy associated with the strong force between elementary particles. But fission energy has the well-known downside of radioactive waste. Much better, it seems, would be a controlled version of the process that powers the sun: nuclear fusion.

Fusion energy has been a dream as far back as I can remember. In my own country, Germany, research programs started in the 1960s aiming in parallel at both magnetic-confinement fusion and inertial-confinement fusion (that is, laser fusion). By the time I started work on my dissertation, research toward laser fusion had been dropped in Germany, but it continued elsewhere, especially in the United States.

Magnetic-confinement fusion became a priority of the European Union and several other areas. Research has progressed step by step, encountering unforeseen problems here and there—as is usual in fundamental science—but overcoming them with enough effort. Progress in magnetic-confinement fusion has been steady and continues today in a promising direction. Only about a factor of five is missing in performance before a meaningful power plant can be built.

Then, in December 2022, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory, USA, which has pursued laser fusion, announced that it had exceeded “scientific breakeven,” creating a fusion reaction that produced more energy than the laser-induced X-ray energy that triggered it. At this high level, scaling up is difficult, and even improvement factors of two can be very challenging. Reaching this milestone was a highly commendable achievement, deserving all the media attention it attracted.

Interestingly, the recent progress in laser fusion has triggered dozens of startup companies worldwide and has made it a hot topic at many optics and photonics conferences. I find this remarkable, because for laser fusion, as with magnetic-confinement fusion, the path ahead is still a long one. Among other things, the scientific breakeven achieved at NIF compares the fusion energy generated only with the light energy actually absorbed by the target to ignite the nuclear fuel. The laser’s wall-plug efficiency is not factored in—and, for NIF, that was low, as was the pulse repetition rate.

There are, of course, new concepts for much more efficient high-power lasers, so hopes are high. But we can still expect a long road to technological success. Along that road, many fundamental questions at the intersection of laser physics, materials science, optics, plasma physics and nuclear physics still must be addressed and overcome. This creates a wonderful opportunity for the younger members of our community.

Like everyone, I will continue to watch the development of both magnetic-confinement and inertial-confinement fusion with great interest. It is remarkable that optics and photonics, like no other field, is paving the way for future technologies—not only in fusion, but also in quantum sensing, communication and computing; in energy-efficient microelectronics; in safe and efficient human–machine interaction; in so many other areas.

Gerd Leuchs,
Optica President

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Publish Date: 01 April 2024

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