60 years of lasers—What’s next?

2020 has been dominated by the global pandemic. Many nations and many people are currently fighting to retain a regular health service or as an individual, to just breath normally. Conard Holton wrote a cautious outlook what we may expect on that frontier in the near future.

If we change the perspective and look at the industrial laser then we see that it has been surprisingly stable so far. Arnold Mayer from Optech Consulting told me on the phone that he expects a limited downturn for 2020 and even a chance for growth in 2021.

In his recent outlook he made some remarkable comments. When global GDP decreased during the 2009 financial crisis, laser demand dropped 45%. The crisis had hit the laser market on the top of a growth phase. In 2020 the GDP will probably shrink more than 5% as the World Bank estimated in November. Mayer sees the laser market contracting by a mere 10%. In contrast to 2009, the pandemic hit the laser market in a downturn phase. Mayer even saw a recovery in the field of microelectronics processing. A sentence I found particularly interesting is the following, “While the price decay for commodity lasers continues, technology leaders successfully sell higher spec and quality lasers at premium prices.” We will return to this point in a minute.

Has the laser matured after 60 years?

While the pandemic took much of the attention in 2020, the 60^th anniversary went almost unrecognized. A number of nice review articles were published, but there was no room for a discussion. Which is a pity, since there are a number of questions apparent. The laser started as “a solution seeking a problem”, as Theodore Maiman put it in the New York Times in 1964. In the meantime, it has conquered many fields of technology: no smartphone, LED screen or computer would work without the impact of lasers. But where does the technology stand now?

It was at the LASYS trade show in Stuttgart in 2013, when Trumpf CTO Peter Leibinger called the laser a commodity. That trend has continued and expanded ever since. Do we see the end of the enthusiastic era of technology pioneers now? As Arnold Mayer said in his report, prices for standard lasers are shrinking. It started with small laser marking devices, today it comprises fiber lasers beyond 1 kW power. Which is actually driven by a steadily growing number of suppliers and a continuous decline of the price per Watt of power from laser diodes as shown by Leibinger in 2013 already.

In the following I will look at three trends in photonics to see if there is still some pioneer’s spirit and what fundamental changes we may expect in the next years.

#1 trend: Quantum technology

We have seen a lot of private and governmental funding engagements for various kinds of quantum initiatives in recent years. So, when will you see the first quantum-encrypted smartphone? Honestly, I do not expect that anytime soon, but smartphone giant Samsung and South Korean telecom provider SK telecom launched the Samsung Galaxy A Quantum in May 2020 already. It includes a quantum random number generator (QRNG) chipset from Switzerland-based subsidiary ID Quantique.

It shows a huge technology push that is coming along with quantum technology: Photonics integration is the name of that game. Taking quantum technology from a lab into a smartphone (or up to the ISS - wait for LFW’s January issue for a nice feature on it) requires a lot of miniaturization and integration of components. Do you remember the big IT hype in the early 2000s? The money poured into telecom industry at that time boosted fiber laser technology which became a game changer in industrial laser technology. A similar effect could happen with integrated photonics.

Integration of photonic components is needed for further empowerment of server farms and large data processing. One could discuss optical printed circuit boards, and any other way to replace electronics by photonics. Once light signals from our common fiber network extend to racks, boards and processors, it may save lots of energy in data centers and speed up processing. Quantum technology is based on light pulses from the very beginning, it uses tiny light sources for single photon generation for example. Advancing established lithographic processes for integrated photonic components will be key for both, quantum technology and optical communication technologies.

How long will it take? The OSA Industry Development Associates (OIDA) published a Quantum Photonics Roadmap earlier this year. Beside their quantum technologies timeline, they also present a long list of optics and photonics component requirements. So, quantum technologies will boost photonics in various ways, it may just take time. At the moment, they look at two decades for the technology to evolve. As big as it is rated, it may take longer to fulfill all the expectations. At least this is what I think when I compare expectations in QT with the early days of laser technology when people thought the death rays would soon shoot rockets down from the sky.

Trend #2: Ultrafast material processing with ultra-short laser pulses

If we look at the last new laser system which entered the market, then this is the ultra-short pulsed (USP) laser. From the viewpoint of physics, it is just a kind of solid-state laser that uses sophisticated tricks to generate extremely powerful pulses as short or even shorter than a picosecond. Thanks to their high intensity they can ablate almost any material in very short times. In a simplified view, the material is blown away before its heat can dissipate into the surrounding. Thus, there are rarely heat affected zones in the adjacent material, which is why the process is often referred to as cold ablation.

Their current limitation lays in processing speed. Ablating some mm³ per minute counts as fast. Which is fine for some micro processing or ultra-precision tasks. But now there are projects evolving to change that. Driven by the German Fraunhofer society, the Cluster of Excellence Advanced Photon Sources (CAPS) plans to drive the source power to an average of 20 kW. In 2020 they started offering 10 kW sources for application development in their application labs in Jena and Aachen.

A crucial point of their project is the development of technologies along the process chain towards real-world applications. Which is essential, since USP process know how becomes essential for higher power as I wrote earlier in 2020. In a nutshell, the power introduced in the workpiece at such high average powers is no longer negligible and one has to know the optimal settings for an optimal process. On the other hand, one can use multi-beam technologies to make use of the increased pulse energy.

13 different Fraunhofer institutes collaborate in the CAPS cluster making it a virtual institute. They have grouped their efforts into the fields of production, imaging, materials and, science. After all, they want to make USP lasers as common on the shop floor as fiber or CO₂ lasers are already. The difference is their sub-micron precision which will open up even more fields of material processing such as drilling tiny holes in airwings to reduce fuel consumption. But as the laser was seen as a solution seeking a problem, USP lasers are expected to find many more applications.

Trend 3: Research on extreme light

In an interview in 2010, Gérard Mourou presented his ideas of extreme light to me. “Towards exawatt laser power and sub-attosecond pulses” sounded quite extreme at that time and it actually still does. But at the same time, Mourou was founding the Extreme Light Infrastructure ELI as a network of three new research institutes in Eastern Europe to pursue his ideas. When he was awarded with the Nobel prize in 2018, most of this infrastructure was about to be completed. Today, all three ELI institutes have operational laser systems now. They do not reach exawatt pulses, but they have and will continue to achieve world records in various parameters. And they are competing with a rapidly growing number of laser facilities pursuing ultrahigh intensities around the world. Pulse powers of 10 petawatts have been shown, 100 PW are proposed or even under construction. New records in focused intensity can be expected in 2021.

Why is this important? There are many reasons. One is that these research institutions educate excellent new laser operators that move directly to industry and handle their laser, as I was told when I visited the ELI facility in Magurele in September 2020. Beside that, a new generation of laser scientists is formed that learns both how to develop a complex laser system and how to conduct experimental research with it.

Of course, there are substantial scientific outcomes to be expected. The high intensity lasers can produce energetic beams of light, electrons, protons, or other particles from relatively compact sources. Extensive programs on materials science and biological or medical research are in place to exploit these capabilities, which are expected to have a huge impact in their fields.

What I found even more interesting is the connection between laser and particle physics. It may seem obvious to feed laser accelerated particles into larger accelerator schemes. That could save money and help to avoid ever larger accelerator schemes. But it is far from easy to connect the two worlds. While laser people think about focus intensity and plasma physics, particle physicists talk about luminosity, and months of continuous beam time.

Interesting research in this field is currently done at the accelerator division of the German electron synchrotron DESY in Hamburg, Germany. Its director, Wim Leemans, has conducted many years of research on laser acceleration at Lawrence Berkeley Lab in California before joining the German team in 2019. In Hamburg, they have shown for the first time 24 hour operation of a laser accelerated electron source. A recent long-term strategic planning report by the United States Department of Energy (DOE) assumes a conceptual design report for a laser based linear collider by 2035. This report is mentioned in the “2020 Roadmap on Plasma Accelerators” which gives a comprehensive summary of what has been achieved in this field. Many problems still have to be resolved, but the progress of recent years gives hope that we may see laser-based electron accelerators within 10 years from now.

This hope is fed by another amazing recent development, which is as ambitious as it is promising. It is a new attempt to laser fusion. Yes, we talk about laser based nuclear fusion for energy generation. What failed at the multi-billion National Ignition Facility is now on the agenda of a Bavarian startup: Marvel Fusion “… will provide a novel approach that is suited for commercializing baseload fusion electrical power. The Marvel Fusion path to commercial fusion energy is based on short pulse, high energy and electrically efficient lasers” they say on their website.

Marvel fusion wants to erect a first test site in the Bavarian community of Penzberg. Construction of the buildings is scheduled to start in May 2021, it should be running in 2023 as local newspapers report. They plan to invest 200 to 300 million euros, which is about the sum that was invested in each of the ELI sites. 150 people should work there in the beginning, they say. A real power station producing a real energy output would cost about two billion Euro and construction could be operational in 2030. The whole endeavor is backed by private funding. Gérard Mourou is member of the Advisory Board, one of the founders of the whole ELI project, Georg Korn, is hired as Chief Technology Officer.

Summary

After 60 years of development, the field of laser research and development is agile and vibrant. We see both, expanding markets where the laser is a commodity, and evolving fields of new research. Just a few fields have been mentioned here, there are more such as industrial sensing or biomedical diagnostics where we see substantial progress.

For the future, the laser will evolve in many directions. It will become smaller and less powerful, in some cases down to single photon emission, if we think quantum. On the other hand, lasers will get ever more powerful, up to a region where it pulls particles out of the vacuum.

While it seems as if the development of entirely new laser types is completed, there are new challenges in driving the existing systems far beyond their limits which will keep laser folks busy for decades to come. Or, as visionary Gérard Mourou promised, “the best is yet to come!”