Interview with Franz Tavella

Our former colleague Franz Tavella is now a senior scientist at the Stanford Linear Accelerator Center (SLAC). He has been working with free electron lasers for more than ten years. He develops laser sources for special applications. In the interview, he talks about his work and plans in his new position at SLAC.

Congratulations to your new position at SLAC. Why did you become a laser physicist?

To be honest, it was plain good fortune. I was enrolled as an undergraduate student at the technical University of Vienna. The „Fourier Optics“ lecture, given by Prof. Georg Reider, the former Photonics Institute department head, really left an impression, and pushed me in the right direction. Shortly thereafter, I met Prof. Ferenc Krausz and I did my undergraduate thesis work in his group, and fortunately, he invited me to join at the MPQ for graduate studies.

 

Can you briefly explain your research to us? How does scientific work in the US differ from that in Germany? Are there any differences?

I primarily develop new laser capabilities at Free Electron Lasers. I did that at the Deutsches Elektronen-Synchrontron in Hamburg, and now at SLAC. Both facilities have a strong focus in the photon sciences. This is my main responsibility, and which has priority. As a scientist I have my own research program. This is encouraged and expected from every scientist. I’ve been working on pulse duration diagnostics for XUV and X-ray pulses in the past years, as well as on the development of X-ray materials for these applications. The experiments have been performed at FLASH and the FERMI FEL in the XUV spectral range and at LCLS between 5-10 keV photon energies. Apart from different bureaucratic practices SLAC and DESY are very similar. There is a constant back-and-forth of scientific staff between these facilities and you very often see familiar faces. The FEL community is still quite small and closed as opposed to the laser community.

 

What does the research environment at SLAC look like?

The research environment at SLAC is excellent in terms of opportunity. Working at FEL user facilities introduces you to many new methods in different fields of science. On the other hand, scientists at SLAC have in some sense, two jobs. One is to keep the facility running for users and develop new capabilities to improve the endstations, FEL and lasers. The other is to perform original research. This can be difficult to juggle.

 

Is there a physical phenomenon that you find particularly fascinating?

Amplified spontaneous parametric down-conversion in a nonlinear optical crystal. Not just because of its manifestation as a colorful cone of light, but as an effect of the vacuum fluctuations. At low repetition rate you can observe the individuals spatial modes randomly flashing across the ring with wavelength set by the „phase-matching“ angle.

 

Finally, let's take a look into the future. What can lasers do in 10 years?

It is somewhat difficult to predict what the future has in hold. I would hope femtosecond high power lasers at longer wavelength to be commercially available in ten years. In the past years, we have seen picosecond solid state and fiber laser systems revolutionize how high power laser amplifiers look like. Novel concepts, including OPCPAs, have squeezed the market share of Ti:Sapphire laser systems substantially. In the next years we will see a shift towards spectrally broadened high repetition rate laser amplifiers up to several kilowatts average power. Due to these developments, laser driven photon and particle sources will find wider access throughout the scientific community.