Interview with Roel Baets
Interview with Roel Baets
Professor at Ghent University and imec affiliate, and an internationally renowned expert in photonic integrated circuits, silicon photonics and III – V semiconductor technologies.
https:// doi. org / 10.1051 / photon / 202614015
Could you tell us about your background and how you became interested in optics and photonics? I studied electrical engineering at Ghent University. During my studies, I was strongly influenced by individual professors, and in particular by Paul Lagasse, who was among the first in Ghent to move into fiber optics. He taught several courses related to optics and fibre optics, and what attracted me was that these subjects felt very new compared with many of the other topics we were studying. I think students are naturally attracted to something new. After graduating, I was fortunate to receive a prestigious fellowship that allowed me to spend an additional year at Stanford University, where I completed another master ' s degree in electrical engineering. I continued studying optics, including a small project with Joe Goodman, who was another inspiring influence, but I also took several courses in biomedical engineering, which was another field that fascinated me. Through these experiences, I gradually developed a strong interest in optics and photonics.
What was the topic of your PhD thesis? My PhD was in integrated optics, within a completely new team working on III-V semiconductor components for optoelectronics. I was very attracted by the idea of joining a team at such an embryonic stage, essentially starting from zero. My PhD combined fundamental and experimental work. On the theoretical side, I immersed myself in the fundamental literature on waveguide optics. Researchers such as Marcatili and Yariv, and in France Claude Vassallo, were among my scientific references. Vassallo ' s book was really my bible for several years. This strong foundation in electromagnetism and waveguide optics proved extremely useful later in my career. On the experimental side, we had virtually no technological infrastructure. I built my own liquid-phase epitaxy reactor, learned from other groups, including during a short stay in Sheffield, and eventually managed to fabricate simple LEDs and laser diodes. Looking back, this combination of fundamentals and hands-on technology shaped much of what I did afterwards.
What were the next steps in your career after your PhD? I completed my PhD in 1984, which, interestingly, was also the year imec was founded. Although imec originated largely from KU Leuven, it was established from the beginning as an interuniversity microelectronics research centre for Flanders, involving other universities including Ghent University. This gave me the opportunity to become one of the first roughly fifty imec employees while remaining physically based in Ghent. We could therefore continue developing our research activity in III-V integrated optics while being connected to a much broader technological environment. During the 1980s, much of my work focused on developing III-V technology. I had started with liquid-phase epitaxy, but it was already clear that MOCVD represented the future. We acquired our first MOCVD reactor and progressively developed the epitaxy and processing technologies required to fabricate optoelectronic devices. That was really the first phase of my career: starting from fundamentals and progressively becoming deeply involved in technology development.
How did your research activities evolve in the following years? Around 2000, we became increasingly interested in high-index-contrast nanophotonic structures and wanted to explore devices at the submicron scale. With the III-V technology available to us, however, our fabrication capabilities were limited. Given our connection with imec, we thought: why not use silicon as a model system? It would give us access to advanced deep-UV lithography and allow us to explore nanophotonic waveguides, microcavities and photonic crystal devices. Only three or four years later did we begin to realize that silicon might be much more than an interesting scientific model system. The idea that photonic devices could benefit from the enormous technological maturity of the CMOS world was obviously extremely appealing. We initially explored passive devices: waveguides, grating couplers, edge couplers and many other structures, taking full advantage of the high refractive-index contrast. Then
" Given our connection with imec, we thought: why not use silicon as a model system? It would give us access to advanced deep-UV lithography and allow us to explore nanophotonic waveguides, microcavities and photonic crystal devices. Only three or four years later did we begin to realize that silicon might be much more than an interesting scientific model system. The idea that photonic devices could benefit from the enormous technological maturity of the CMOS world was obviously extremely appealing."
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