Personal interview of Prof. Humeyra Caglyan

Humeyra Caglyan, Professor at Experimental Optics and Photonics, at Tampere University is developing meta optics and meta materials

Humeyra Caglyan, Professor of Experimental Optics and Photonics, is focusing with her group on engineering the fundamental interaction between light and matter at the nanometer scale.

Main research topics are metamaterials, plasmonics, and quantum nanophotonics.

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Humeyra Caglayan, Professor in the Photonics Department, what has been your path to becoming a researcher?

I started as an assistant professor in June 2017 at Tampere University, about five years ago. I started in the photonics department, and when the university merged, I moved one step ahead in my career. I was promoted in 2019 to associate professor in the physics department. But, of course, we are still doing photonics in the photonics unit.

I got my Ph.D. at Bilkent University in Ankara, Turkey. Bilkent University is one of the best in Turkey, especially in this area. After my Ph.D., I moved to the United States, where I did my postdoctoral studies. Then, I moved back to Turkey shortly before I joined Tampere Technical University.

I have been working on metamaterials since my Ph.D. studies, and over the years, I have developed different applications and changed the research a little bit. But we are still working in my team on metamaterials and plasmonic devices. During my Ph.D., I concentrated more on fundamental research. It was a sparkling moment when the metamaterial research idea started. Now, the research is directed more toward technologies; also, my team is developing devices based on the development of this fundamental research. Right now, we have one ERC project, which started in 2019. That is also based on metamaterials, but the application is on the quantum optic side. We have recently achieved some good results on that.

It’s a five-year project, and we hope to develop an environment that can be useful for quantum communication even at room temperature because, currently, quantum systems need an environment that needs cooling. Such conditions may not be suitable for every place to have it. And if we can eliminate this requirement of having to cool down with the systems we have developed, it might be beneficial.

Metaoptics and lenses

Another recent project, which we have started and are now actually combining metamaterial-based optics (meta optics) for imaging applications.

Researchers have been developing optics and optical materials for lenses for many years, and this research is critical when you want to use them on your mobile device. Of course, in the past, we didn’t have cameras on phones or laptops. The big cameras were excellent, and we could have bulky optics for high-quality photos. The most significant part of these cameras is the lenses to capture the light effectively.

Nowadays, the main problem is that we want many cameras on our phones, and they must fit in minimal space. The aim is to shrink the lenses as much as possible without losing an image's properties and quality. And further, we don’t want the camera to spend much energy and run out of your battery, but able to take long hours of videos. These are the goals of this research.

Now, new optics has been developed. This is called meta optics, which is based on metamaterials. Meta optics have the properties of an optical element, for example, a lens, but in a much, much thinner space without the need for a large volume. This lens is only a few microns thick compared to a centimeter.

We want to get the best images with these meta-optics.

Have you been developing the material itself?

We have been developing metamaterials, so-called engineered materials, and modifying the surface with nanofabrication to obtain meta optics. Otherwise, it’s just material and cannot act as the required lens. Over the years, nanofabrication has developed quite nicely, so we can now fabricate high-quality structures to obtain meta lenses, which can create high-quality images.

Of course, this is only the hardware side of this story. This must be supported with image reconstruction software. There are good developments in software as well; many companies have developed different software applications for a long time.

Our colleagues at the university are also developing the software part as part of the research project. So, there are many opportunities along the line, but the first step is to make this efficient and very thin lenses.

Future plans - light field microscopy in the university as a prototype

We plan to develop meta-optics for biomedical microscopy. This can help biology researchers because there are some requirements in biomedical imaging, such as they want very low light exposure to the specimen. Light exposure for a long time may kill living specimens, and this may limit the ability to observe fast changes. The idea is to use meta optics and obtain 3D images without scanning. This new microscopy can provide high-quality volumetric images in a single shot without exposing much light for a long time.

One must scan each of these layers to image a 3D-dimensional sample with current microscopes, which is very time-consuming. Thanks to these newly developed optics, we can focus on the target without scanning with one single shot. There is a considerable time saving and an opportunity to investigate live samples at a different level, so this is another excellent application.

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Meta-devices

We call these developments meta-devices. They can be either for imaging or communication applications. The idea is to make them more efficient, functional, and less energy-consuming. This is our most important aim.

Different people in the team are working on various applications. They may seem too separate from each other, but at the core of what we do is design those metamaterials, optimize them, fabricate them, and test how they work.

How big is your team, and how do you collaborate within the group?

My team currently has three Ph.D. students and three postdocs. We have a changing number of bachelor and master thesis students; currently, we have 4 MS thesis students. They usually complete and go in a shorter time, and we also host guest visitors from other countries from time to time.

Our work depends on different aspects. Initially, it requires an optimized design and then fabrication in the cleanroom facility that we have at the university. Once the samples are fabricated in the cleanroom, one needs to test them and characterize them. People may have different strengths and interests, and if one is getting better fabrication and the other is more towards characterization, then these people can collaborate on the same project. Everyone is somehow collaborating on a project with another person.

A single person can't complete the project. Therefore, it’s always at least two to three people working and helping each other. And, of course, it’s always good to know others’ opinions and contribute and discuss them. Often, we start with an idea, but during the discussions, we end up with something much better and eliminate some of the ideas. So, it is always good to have a team instead of working alone.

How you ended up doing research?

Even when I was very young, I always wondered how things, especially in nature, work. For example, I remember myself in elementary school wondering about the Moon passing between Earth and the Sun, the solar eclipse.  It was super interesting for me to know how that happened. I remember asking my elementary school teacher about all these and many more. That was super fascinating for me to understand how nature works.

I later loved every aspect of physics, but even then, I was amazed by light. Then, over the years, I pursued being a physicist to understand how things work and how we can explain them, especially light-based phenomena.