Interview with Ernst Fill

Since the 1970s, Dr. Ernst Fill has been working in laser science. He first encountered laser science as a young postdoctoral student working at the institute for plasma physics in Garching. Today, he is still an active member of the attoworld-team for laser development.


Again, happy 80th birthday. You are still working in the LAP team for laser physics. Does laser physics keep you young? Or is there another secret?

Thank you very much. There are three contributing factors that aren’t really secrets, though. I keep an active lifestyle and enjoy hiking, cycling and paddling. I also try to maintain a healthy diet - I eat lots of salad and avoid sweets. Thirdly, science keeps me young, too, of course. I am always looking for new challenges and enjoy figuring out what is technically feasible.


How did you end up in physics?

Even when I was in school, I loved building radios. Back then, my parents gave me a radio kit. With radio valves, of course. With the tools from the kit you could build a well-functioning radio. Together with a friend from school, we invented all sorts of circuits. It fascinated me that you could create good music from invisible waves. My father recommended I study physics. I then studied physics in Innsbruck, an hour away from my hometown, Kufstein.


When did you start your career in laser physics and what got you interested in this field?

I was working as a postdoc in the USA doing research on ultrasound. In 1970, a research group was developing a new neodymium laser at the institute of plasma physics in Garching. Naturally, laser physics was much more interesting than the more conventional ultrasound. That is why I applied there. In 2003, I joined the team of Ferenc Krausz when he became director of the Max-Planck-Institute of Quantum Optics (MPQ).


Please tell us what it was like back then, when laser physics was still at its beginnings.

I started working in laser physics in 1970, the laser had been invented about ten years earlier. Nevertheless, there was still that spirit of adventure. Constantly new laser lines and materials were invented. Research was concerned mainly with the new effects of laser light. When it came to the practical uses, there were no limits to your creativity. Not all of them were successfully realized, as in the case of the laser-fueled rocket. Unfortunately, there were many demands for military uses, too. The Strategic Defense Initiative (SDI) even wanted to install lasers as ballistic missile defense in space. The real pioneers in laser sciences were skeptical, however. There is the comment by Schawlov when asked whether lasers could be used for military purposes: “Yes, if the enemy comes in balloons.”


In what ways has science changed until now? Was research conducted differently compared to today?

It was not much different back then. Maybe we experimented more and occasionally strayed from the line. Sometimes this led us to unexpected results. One time, we irradiated mercury iodide with UV-light from an argon fluoride laser. The idea was to find a reversible iodine laser medium. We were quite surprised when we did not create iodine laser light, but blue and green light - we had turned the mercury into a laser! As you can see from this example, our way of working led to a high number of publications, but not necessarily to better results.


Why are you fascinated with laser physics?

Laser physics opens up new possibilities of exploring the law of nature as well as providing many interesting practical uses.


What importance will laser physics have in the upcoming decades?

I believe that the possibilities offered by the laser, in fields such as medicine, and environmental and climate protection, are by no means exhausted.