Get to know our MPSP Fellows: Nicolas Joly

An Interview Series

In today's interview, Prof. Dr. Nicolas Joly shares some exciting insights into his field of research, photonic crystal fibers.
He is head of the „Microstructured Optical Fibres Research Group” at the Max-Planck Institute for the Science of Light and associate professor at the University Erlangen-Nuremberg.

Could you explain the main focus of your research in photonics and what initially drew you to this area of study?

I'm using photonic crystal fibers. These are fibers that were invented in 1996 and basically first demonstrated by Professor Russell. I basically chose that topic after my PhD, and since then, I haven't left because it was fun. And what I particularly liked was that we can make those fibers by changing the geometry of the fibers. The photonic crystal fibres (PCF) are made of tubes that you arrange in a different configuration. And then by changing the configuration, the size, you can change the property. It's a really nice playground. I really consider this playing with the fibers. And since I saw the fabrication facilities and all that we can do with those fibers, I thought, “Wow, this is really cool”. And now it has basically been 20-something years since I started working in that field.

As a fellow, what has been your biggest challenge in the field of photonics, and how did you overcome it?

I didn't know anything about quantum optics. And then once I discussed with Maria Chekhova, I realized that there were many things that I don't understand at all. And then I convinced her that the way I was looking at the problem was not so stupid. And so, we started working together, but then I had to learn quite a lot. The challenge was changing that pure photonics fiber optics to use it for something. But at the end, I also took that more as fun, rather than a real challenge.  So yeah, I think the challenge is not purely photonics, but to convince people that what we do is interesting enough for them to finance it. That's the main goal and challenge.

Collaboration plays a major role in research. What's been your most rewarding collaborative experience, and how did it affect your work?

I think there are two major collaborations I had in the past. One was with the U.S., as I was a postdoc. It was the beginning of everything. I got the chance to go to the U.S. when I was a postdoc, and bring them some special fibers, which has never been done before.

I had to make the fibers and then develop the fibers. Then I went there to do the first experiment and identify which fiber would do what exactly. They did the measurement. We basically got an insane number of publications afterwards. That was really rewarding, of course, because it probably also helped me afterwards, convincing the people that I could stay in that sort of field. But this collaboration is long gone, and I didn't initiate it.

But the most rewarding collaboration is definitely the one I have with Maria Chekhova. Because that is something I initiated by asking a simple question over a coffee. We discussed a few times, and then we started working, and that was more than almost 15 years ago, and we are still working together. So, that's the rewarding thing, because I think we are really complementary. And that's a good thing.

What are some of the most surprising or unexpected applications of photonics that you encounter in your research or studies?

The experiments that we're doing at the moment, are really, really fun. They basically took a direction, which was absolutely not expected. That's probably one of the things that is most rewarding. Again, once we tried something for almost two years with the students starting from managing to convincing the finance agency to give us some money for something that really was sort of a high-risk, high-impact. But we were a bit too much into high risk. So, it just didn't work. Consequently, we had to completely change, it was kind of difficult for the students. But now we are seeing so many different phenomena, that is really fun. Every day, the students comment, "I saw this, I saw this, I saw this", everything is new every time. It's really interesting and rewarding somehow, and surprising. I didn't expect this. We just try something and then it finally works. Of course, that's the results of two years of fighting, fighting, fighting to get things working. And suddenly, when something starts to work, everything starts to be super easy, because we had to sort out issues, which were much more complicated, which we eventually had to give up on. In that sense, this is the surprising thing.

What advice would you give to students or early career researchers aspiring to make an impact in the field of photonics, and how can they stay motivated through challenges? 

I think the question is not the right one. Because I don't think that the student should be motivated by the notion of wanting to make an impact. I think they should think “oh, that's very interesting and I will learn a lot from that”. I'm talking about the PhD students. I don't think that the motivation should be, “I'm going to make a big impact there”, because I think we should be driven by curiosity first. And then if on the way, after two, two and a half years, we realise “oh, wow, this has a really big impact”, this is good, this is like sugar on top. But I think it's more like being driven by curiosity, rather than thinking we're going to make a big impact. This can come later, in my opinion.

How does your research at the Max Planck School of Photonics differ from your previous experience in photonics, and what unique opportunities have you found here? 

One of the good things is, it brings in very smart students. My feeling is that if I compare with a few years ago, the quality of the student is improving a lot. That's really nice. And I really enjoyed all the discussions I had at the annual meetings, for instance. This is something I really enjoy. On top of that, I talked to Christine Silberhorn and Maria Chekhova, and this conversation may lead to some interesting new projects. That's the networking aspect, which I think is very interesting within the MPSP.

I mean, we've also been working a lot on this joint degree. I was as a member the curriculum, we did meet every week for a really long time with Carsten Rockstuhl and Thomas Pertsch, and a few others to basically set this up. Now it is in good shape, not there yet, but in good shape. And I also think that this will give us some unique opportunities to transfer knowledge and motivate students.

Looking ahead, what excites you most about the future of photonics? 

I mean, one of the most exciting things in photonic crystal fibres is the fact that now these fibres can beat the telecom fibres, they are better in terms of losses. It's clear that this will drive the research a lot, because there are more and more people who are interested in those fibres. Companies and other parties want to have a part of the cake, so to speak. And I think that more people in the game will, of course, make things harder, but also more interesting. The field of photonic crystal fibres is totally exploding at the moment.

Other fields will probably also have an impact, but considering the latest results in the photonic crystal fibre field, where they are beating other fibres, that's really something which has an impact.