Lasers, colors, pictures

When she was in high school, Dr. Rocío Borrego Varillas’ interest began in Optics. She didn’t know whether she wanted to pursue a research career, or even knew what that meant, but still, an image of herself moving around lenses in a lab was taking shape.

She did her PhD at the University of Salamanca, her hometown in Spain, working with ultrashort and ultra-intense lasers. Her project was focused on the optimization of non-linear processes, such as the second-harmonic generation, optical filamentation or supercontinuum generation. They wanted to validate different schemes to enhance the pulses obtained through these processes. For example, how to achieve shorter pulse duration, increase the energy or to modify the color of the laser light for different studies.

Rocío is currently doing her postdoc at the Institute Politecnico di Milano (after obtaining the prestigious and competitive Marie Curie fellowship) and is working on generating ultrashort light pulses and applying them to the study of ultrafast phenomena in matter. This is an ambitious project unifying efforts of groups from different fields.

<p>Dr. Rocío Borrego Varillas, back at the lab right after our interview.</p>

Dr. Rocío Borrego Varillas, back at the lab right after our interview.

Thanks for your time today, Rocío. I think the obvious question to start with is: How did you decide to get into research? Was it a clear election when you finished your graduate studies? 

It was not obvious to me when I started my graduate studies in Physics, because I didn’t have a clear idea of what doing research really meant. It was during the last year of my graduate studies, when I obtained a grant and got some research training helping the researchers from the Optics Department in their studies, that I took my first steps in this field and got trapped in it.

And why did you choose Optics? What did you find special in this field with respect to others?

I liked Optics ever since I had a subject about it at high school. I liked it from the beginning because it is something very intuitive, very visual and not abstract like other subjects. Instead it is something you can find around every day. And I also liked it because of its multiple applications, like lasers, telescopes or the study of the eye.

Your PhD work was focused on studies with ultrashort and ultra-intense lasers. What makes this type of lasers special? And what are their applications?

As opposed to other types of light, such as the one emitted by a bulb, a laser is a source of coherent light, and therefore it can concentrate very well the energy. Ultrashort lasers emit light not continuously but in very small fractions of seconds, increasing in this way their power immensely. This can be applied for instance to particle acceleration: it is already used to accelerate electrons and now started to accelerate protons as well.

This means that maybe in the future, we can have the same processes observed in today’s particle accelerators like the one at CERN, but with a laser instead- which is a device that is smaller and less expensive. Also, because it is so short, it makes it possible to take pictures of events happening in a very short time, like for instance, the dynamics of a molecule.

And now your work consists of applying the research carried out during your PhD to study the effect of those laser pulses in matter…in taking those pictures.

Now I am doing spectroscopy, studying the interaction between laser light and matter. For these studies we need to use optical parametric amplifiers (OPAs), to generate a laser source in different spectral ranges. The reason is that the wavelength of our laser is in the infrared (IR) spectrum, but to study for instance a photosynthesis process, the light we need must be in the visible spectrum, or in the ultraviolet (UV) so that we can study the damage in DNA – which is what I am doing now.

Once we have those laser sources, we use them to excite the system we want to study (DNA, the reaction center of the plant doing the photosynthesis, graphene…). The material or molecule is pumped with this laser source, and then a second pulse called probe, created with the same laser but possibly in a different range than the first one, allows us to track the dynamics of the system. In this way we are taking a picture of processes happening in very short timescales: it takes only about 100 fs for an excited DNA molecule to decay to the fundamental state.

Do you get to learn more about other fields collaborating in this interdisciplinary research? 

I try to learn a bit of everything, since I have the chance to collaborate closely with people from different fields and institutions. We meet to discuss the material we need for the studies and the results we obtain. At the moment, we work with chemists from Bologna, who provide us with the simulations we need, and with biophysicists in Viterbo, who help us to prepare the samples we need.

Can you briefly describe how your usual working day looks like? Do you spend many hours at the lab?

It depends on the day; some days I have to do more work at the computer to work on data analysis, but yes, I usually spend most of the time at the lab. I have been lucky so far and never had to spend a night at the lab, but some of my colleagues have. It happened when they had to do long measurements and  didn’t get to stabilize the laser until late evening.

How did you first get in contact with the group you are working now with in Milan?  

I learned about this group through their papers; during my PhD I read many publications authored by them. Later on, when I heard about the Marie Curie actions, I talked to my supervisor and colleagues about potential groups to apply with, and I thought about them. I wrote them an email and we had a phone meeting to discuss about it… it was like meeting famous actors from your favorite movies!

That is an excellent example of how worth it is to spread your own work! While doing your PhD, you won an outreach contest. Do you think it is important to stimulate and invest time in communicating science from your own Universities and research groups?

Yes, for a double reason: firstly, to disseminate knowledge and teach about the research carried out at universities. And secondly, I think it is important to bear in mind that most of the research projects are funded with public money and, as a citizen, I would like to know how the money from my taxes is invested.

But I guess it is not always easy to find a compromise between doing research and spreading these results to a wider audience, right? 

Sometimes it means you have to add extra effort to your workload and you have to dedicate the time. In my case, it was not difficult because I liked doing it – I didn’t reduce the time for research, I actually worked on that during my free time.

Moreover I was used to explaining my studies to my friends, so I already had a sense of which concepts could be the most difficult ones to understand. Nevertheless, there are initiatives from the universities themselves to help scientists in spreading and communicating their research work such as promoting open doors days, contacting schools or high schools to visit the institutes, and so on.

And that has not been your only outreach project… 

Indeed, I also collaborated in the publication of a book with other students from the Optics group in Salamanca, as an attempt to improve the knowledge about the laser in the society. It was a project  to mark the 50th Anniversary of the Laser in 2010, and a very rewarding experience. Then the book was freely distributed to the libraries of universities and institutes in Spain.

Well, I hope you will have many other projects coming! 

Me too! For the moment, I like very much the work I am doing in Milan and I will stay one year more here.

The book Rocío edited together with other students, “El láser, la luz de nuestro tiempo” is available for free download (in Spanish only) from the Optics department’s website at the University of Salamanca. You can download it by following this link.