Flexible Opto-Electronics Laboratory, School of Electrical Engineering and Computer Science (EECS), Gwangju Institute of Science and Technology (GIST), Korea

(1) Please tell us about your career path – what got you interested in optics, how did you come to be in the position you are now? 

I initially pursued graduate studies in semiconductor devices, where my first project involved VCSEL, a semiconductor laser. At first, I wasn’t too interested, but my fascination grew when I observed light emitting from a device I had created. It was astonishing to see light suddenly coming from a seemingly ordinary piece of rock. After that, I began studying more in-depth and encountered various optical devices, which sparked my curiosity to explore the mysteries of light. I discovered that many structures required for these optical devices were either inspired by or very similar to those found in nature. For example, the DBR (Distributed Bragg Reflector) necessary for VCSEL (Vertical Cavity Surface Emitting Lasers) can be found in butterfly wings and fish scales, and the nanopatterns applied to solar cell surfaces resemble the surface structure of moth eyes. This naturally led me to become interested in biomimetic optical devices, ultimately bringing me to where I am now.

“my fascination grew when I observed light emitting from a device I had created”

(2) Do you have a role model that you aspire to? 

I don’t have a specific role model, but I greatly admire individuals who develop new theories or technologies in their research fields, contribute to society, and nurture outstanding students. For example, my postdoctoral advisor at Northwestern University, Professor John Rogers, is a pioneer in the field of flexible electronics. He not only conducted research in this area but also explored various applications, making his findings applicable in electronics, medicine, and environmental fields. He has also mentored many successful students. In the field of optics, although I don’t know him personally, I admire Professor Shanhui Fan from Stanford University. As an expert in photonics, he and his students developed Passive Radiative Cooling technology to address climate change and energy issues. His papers have inspired me greatly. Since I am working on a camera that mimics animal eyes, I also respect researchers who have long studied animal vision, such as British Researcher Michael Land. Their research quenches the intellectual thirst of engineers like me and provides the foundation for creating new technologies. His book, “Animal Eyes,” serves as a textbook for me.

(3) What inspires the work you do? 

My first foray into research on biomimicry was sparked by the nanostructure found in the cornea of a moth’s eye. When I was in graduate school, I was researching ways to improve solar cell efficiency and discovered that moths, which are primarily active at night, have a structure in their corneas that minimizes light reflection in order to capture as much light as possible. I thought this could also be applied to solar cells, as reducing light reflection is crucial. Simultaneously, I became interested in insect compound eyes, and during my time as a postdoctoral researcher at the University of Illinois at Urbana-Champaign, I researched cameras that imitated insect eyes (Nature 2013). After that, I started exploring the idea of developing customized cameras for various applications, moving away from merely imitating human eyes, and began researching cameras that mimic different types of animal eyes. We examined the unique optical structures of fish eyes (Nature Electronics 2020), fiddler crab eyes (Nature Electronics 2022), and cuttlefish eyes (Science Robotics 2023), and created cameras that imitated them.It’s also fascinating to consider the differences between nature and our creations. Nature’s structures are primarily composed of organic materials, while we can use semiconductors and metals. This allows for various transformations and entirely different applications. For instance, there are several theories about why zebras have their striped structure. One idea is that the distinct temperature difference between the white and black stripes can create convection, resulting in more effective sweating and lower body temperature. We focused on this “distinct temperature difference,” connected a thermoelectric generator to it, and used it to energy harvesting from waste heat (Science Advances 2023).

“Without a doubt, one of my biggest inspirations lately is nature itself. I believe that nature offers countless hints and insights. The goal isn’t to replicate nature’s structures or organs exactly as they are (which is impossible anyway), but to naturally draw inspiration for new technology while understanding the underlying principles.”

(4) What do you think the big discoveries in your field will be in the next 5-10 years? 

I work on the development of future cameras. As you may know, current smartphone cameras have very small pixels, about 0.7 microns in size. However, they still cannot keep up with the thinness of smartphones because they need multiple lenses. I believe that research on simplifying camera structures will dominate future markets. Some people are trying to use metalenses, while others are working on curved image sensors. It’s unclear which approach will be more successful. Moreover, current cameras only collect data without decision making like an animal’s brain. Therefore, we need to apply various image processing methods to extract the desired information from the captured images. I think future cameras will incorporate processes for quickly identifying key information within the camera itself. Neuromorphic semiconductor technology will likely play a significant role in this regard.

(5) If you could pick one book to serve as the starting point for the pursuit of optics, what would it be? 

For someone starting with optics, I would recommend the classic textbooks “Optics” by Hecht or “Introduction to Optics” by Pedrotti. Since electromagnetics is also important, I would recommend “Fields and Waves” by Cheng. However, if you’re looking for inspiration, I’d recommend “Animal Eyes” by Michael Land.

(6) If you could give one piece of advice to a student interested in optics and photonics, what would it be? 

I would advise them to focus on what they want at the moment, rather than just following trends. Also, I would encourage them to listen to the research and opinions of others, as indirect experience can be very helpful.

(7) In your opinion, what is the most amazing thing about or in optics and photonics?

I am not very familiar with complex and advanced optical technologies. However, if I were to look for the most amazing thing in my surroundings, it would be that products related to light are always present in the most frequently used items by people everywhere. I cannot imagine how many optical technologies are involved in smartphones. I think this is probably because visual information occupies a significant proportion of human sensory organs.