“I want to tailor light in all its features into novel applications”

Prof. Denz, on which scientific topic are you working right now?

We’re currently working on the development of so-called “optical tweezers” for applications in biomedicine. These optical tools can hold and move smallest living objects such as cells or bacteria acting as a trap for in-vivo objects. We are even capable of manipulating from a few dozen to over a hundred cells simultaneously by using holographic techniques. Moreover, optical tweezers measure unimaginably small forces corresponding to a millionth of a millionth of a gram. For this purpose, we employ nanoparticles as probes, which, in the cells, measure forces acting on cell compartments or during cells migration. Optical tweezers also allow identifying the elasticity of a cell, which is a major indicator of nowadays most devastating diseases such as cancer or Alzheimer disease. Using several tweezers in parallel to investigate the elastic properties of a living cell at different locations paves the way to analyse inner cell compartment or cell-cell interactions as well as larger cells compounds. Biomedical specialists in particular are excited about the potential offered by optical tweezers. They can investigate living organisms in vivo without destroying tissue during the process, and at the same time, they gain tremendous information about the biomedical properties of cells. This helps to explain hitherto unknown processes of cell development, internal cell distribution and cell diseases. We as physicists provide support in the implementation of this established technology in biomedical labs, and continue to develop it jointly with the biomedical specialists and tailored to their specific research question. In this way, we adapt our technology more and more to our colleagues’ needs.

What characterizes you personally as a scientist?

Born in Frankfurt, Main, Germany, I studied in Darmstadt, Germany, and since that time I dedicate my research to the young field of nonlinear optics. For my PhD, I stayed at the Institut d’Optique in Orsay near Paris, France, where we developed holographic data storage into a new direction – and we were quite successful: I was awarded the Lise Meitner Award of the State of Hesse for my PhD thesis. This was a progressive award in those days because it supported young females in balancing work and life. Since 2001, I am a Professor of Applied Physics at University of Münster, and since 2003 Director of the Institute and holder of the chair of Experimental Physics. I am proud of my `Nonlinear Photonics’ team because we pioneered over the past few years a number of significant, path breaking achievements in the field of novel artificial photonic materials and biomedical microscopy. A field that is very close to my heart beneath nonlinear optics is our hands-on experimental pupils laboratory, MExLab Physics for short, where young scholars can explore photonics with own experiments and experience how fascinating light is. Thus, we are also able to interest girls for STEM. Light is not only tough science. Light is also art, colours, and life. Our concept has found up to now many imitations. We thus received a prestigious countrywide award as being recognized as a “location in the land of ideas” for our project “Light up your life” within the initiative “Germany – Land of Ideas”.

What is your big aim as a scientist?

There are already many applications with light. However, the potential of light as a motor for new developments is far from being exhausted. My dream is to develop our basic understanding of how to modulate and tailor light in all its features into novel applications. Light has so many fascinating properties, which have not yet been transferred into applications, as for example polarization. We have used polarized light to build cages of light as novel optical tweezers. They can open and close solely by light thus enable loading and discharge of medical cargo at desired places in a cellular environment. Or take the property of coherence, which allows looking deep inside organisms. Light either is also able to create novel, artificial materials – either by mimicking nature or by creating structures that are not present in nature yet. We are dreaming of fabricating better wave guides, solar cells, or microscopes exploiting these techniques. This is my big aim: tame light to create entirely new devices.

What is your favourite “toy“ for research – and what can it do?

For me, my toy is an almost simple everyday device – a so-called optical light modulator. Actually, everyone knows one – it is in every modern cellular phone: the display based on liquid crystals is nothing but exactly such a light modulator. Every pixel of it gets lighter or darker by an electric field. The great thing about it is that you can use it to imprint any structures you like onto light beams – images, patterns, or whatever you want – and thereby transform a simple light beam into a fascinating light landscape. Light becomes utmost versatile using spatial light modulators.

Can you remember your happiest moment as a scientist?

It is always a happy moment when you have been working for a long time on an extremely difficult research question and suddenly, after a lot of painful thinking, you find a clear and convincing solution – either for an experiment or an equation to be solved. It is absolutely great, in particular, when you had to go through a long dry spell and needed a lot of time to find the solution.

And what was your biggest frustration?

I am always especially frustrated when working conditions are not matching. For example, when we as scientists have to fight with bureaucratic processes, which appear to have no rhyme or reason. Of course, administration is part of every researcher’s life and has its justification for teaching, third party funding, or the organization of a laboratory – but bureaucracy for its own sake can really make me angry. I’d much rather spend the time in the lab.