Interview with prof. dr. em. Djan Khoe

Professor Djan Khoe (born 1946) is one of the pioneers in the field of optical telecommunications. He has played a pivotal role in setting up the COBRA research school in its present form. He is a successful inventor, and has been granted 45 United States patents. He is the author of over 400 publications, and is an IEEE and OSA Fellow. Among other positions, he has been President of the IEEE/LEOS. Prof. Khoe has been board member of several international centers of excellence in photonics, as well as  of the Netherlands Academy of Technology and Innovation.


"My activities for COBRA go back to the time when I worked at Philips Research Laboratories, Eindhoven. Back in 1973, I started working as a researcher in optical communication systems and enabling optical technologies. It was a thrilling experience to work in a field that did not exist yet. We had no lasers at the time and no optical glass fiber.

What I learned most from these years at Philips is that, in optical communications, you can only be successful if you cover the whole field of research. This means that you have to have firsthand experience with an immensely wide range of subjects: from the theoretical physics of lasers and photodiodes and the details of communication systems to the engineering technicalities of electronic devices. We could gain an incredible momentum at Philips, because management fully understood the importance of this integral approach. For instance, as we were still figuring out how optical fibers could be mass-produced, management put together the knowledge of experts in industrial glass at Eindhoven with the experience of people at the lab in Aachen who focussed on plasma technology for silicon dioxide. There were regular meetings between the groups, and advanced commissions overlooked the overall progress. There was a strong culture of solidarity and sharing results. This strategy proved to be extremely successful: Philips produced the best optical fibers available at the time, and won several contracts for field trials in the Netherlands and in Germany.

Later the telecom section was sold to Lucent Technologies, and  Philips went on to focus on lasers and silica fibers. Philips was a major player in laser research, also because of the development of the compact disk. Yet the lasers used in a CD are only made to work for 2000 hours or so. In optical telecommunications, you have to have optical semiconductor lasers that must last a hundred times longer. The most successful product of Philips in the field became the silica fiber, launched through the Philips Plasma Optical Fibre Company in Eindhoven.”

TU Eindhoven

"With this industry experience of collaboration, and what is now commonly referred to as a cross- and interdisciplinary approach, I started my part-time position as a professor of Telecommunications at the Eindhoven University of Technology (TU/e). The research was new, and my department was located within the Electrical Engineering faculty. I immediately felt that if we merely put electronic engineers on the challenges that optical telecommunication faced at the time, we would not get very far. So I started talking with professors from other faculties at the TU/e, and I managed to get a few fine, interested researchers from the Physics and Chemistry areas. I also accomplished to convince the leaders of three faculties of the need of research collaborations within the university. Next, we came up with this daunting plan: we wrote a letter directly to the Dutch Minister of Science and Technology, urging to recognize TUE as a center of excellence for the area of optoelectronics. I had the letter signed by eleven professors (in total) including three deans. We bypassed the Board of the University, because the odds of getting such a letter up and running through the highest official structures were close to zero.

Apparently, that action made quite an impression on our Minister. He decided that the Technical University of Delft should focus on microelectronics, the University of Twente should focus on sensors, and the TU/e became indeed a center of optoelectronics.

Then I pondered over the question of how we could establish a Dutch inter-university consortium. I learned from my experience at Philips that research alliances have much more chances for funding in the Netherlands and in Europe then single institutions. So our strategy was not to pursue the elimination of photonic activities in Delft and Twente but to invite them to work with us. Our executive board was delighted by the decision of the minister and was very helpful in convincing their colleagues in Delft and Twente to collaborate with us. So, back in 1994, I myself, together with Prof. Meint Smit in Delft and Prof. Ton Koonen in Twente, we started the Inter-University Research School on Communication Technologies Basic Research and Applications (COBRA). Prof Joachim Wolter from our Physics Department became the first Director.

In the meantime, I learned that many research fields in the Netherlands were supported via labelled funding, so targeted at specific fields of research. We managed to have funds that were labelled for microelectronics to be partly labelled for optoelectronics. Later we convinced the ministry of Economic affairs to start a funding programme called IOP (Innovatieve Onderzoek Programmas) Electro Optics."


"To me, COBRA was nothing less than launching the era of photonics for communications in the Netherlands - at world-leading level. Already in the first four years, we achieved fantastic research results. Just to mention a few highlights: I myself did research in the field of high speed transmission and broke a world record together with Philips Research.  The Arrayed Waveguide Grating (AWG) was invented by Meint Smit, and is now a commonly used key building block in any optical wavelength division multiplexed communication system. It is fairly safe to state that anybody using the Internet also uses AWGs. COBRA introduced MMI-couplers to semiconductor-based integration technology. MMI-couplers are presently the most frequently used couplers in photonic integrated circuits (PIC). Further, COBRA researchers were the first to demonstrate electrically pumped lasing operation in metallic cavities with dimensions well below the diffraction limit. I expanded our application field towards systems for near or in the house, and I started research in Polymer Optical Fibre (POF) systems, in close collaboration with Professor Koike at Keio University. We broke subsequent world records in that area.

So, in all of our research fields - materials, systems, devices - COBRA showed world leading performance from day one. After the first four years, we were granted a record award of 35 MUSD and the qualification of “Top Institute NRC Photonics” by the Dutch Administration, through an open tender organized by the Dutch National Science Foundation NWO. The grant was given for a 10-year research program in the area of long-term research in Photonic Systems, Devices and Materials. Recently, the Dutch Administration decided to extend the funding for additional five years. During all those years, we managed to double the NRC funding via Dutch and European projects. This is an indication of established quality. Our strategy is to reduce administrative  burden, so we generally focus on getting large projects funded.”


"No one expected us to get the NWO award, because the catalysis-group at Eindhoven was supposed to get it, and it was commonly thought that the award would only be given once to the same university. But I thought: even if chances are low, let's go for it! It was our strategy to make a choice among the many participating groups and to present COBRA in a lean and very clear form. We wrote a very sharp application document, including only my group and the groups of Meint Smit and Joachim Wolter,  concentrating on our three focus areas - materials, devices, systems. And then we got it. This was of course a major success for our group. The total of 35 MUSD in funding was much more than what you would get with what is considered the most prestigious award in the Netherlands - the Spinoza prize. This unique achievement subsequently motivated Meint Smit and Ton Koonen to move to Eindhoven.”

Quality first

"One of the things we have always been very careful about is to put quality first. So, we have always been very selective with applicants for any position. It is better not to have a student in a project at all than to have a mediocre candidate - even if that means that you will miss deadlines for a specific project or lose funding. For excellence is not something you get with just a few brilliant people in a team - you have to share the same level of eagerness, openness and brightness in your team, and then grow a shared sense of excellence. You have to “hardwire” excellence in your organization.

External evaluation is essential for that. We seek  international external experts for all evaluations - even PhD candidates get two international members in his or her evaluation commission. Awards are also a form of external evaluation. So, I have always encouraged our team members to apply for awards.

Quality also means: you have to be original. Researchers who only follow general trends will have difficulties to maintain a leading position. We were always very critical in observing what others are doing. It is fatal if you just follow the research fashion of the day. Instead, our attitude has always been: ‘if everyone tries A, start doing B’. So, if everybody was doing Wavelength Division Multiplexing, we would keep doing our work on time devision mulitplexing. Now it is common to work with all kinds of materials in photonic ICs, but we are still concentrating very focussed on III-V semiconductors.”


“Since my retirement from the TU/e and COBRA, I work voluntarily as a coach for researchers who want to apply for awards. In the Netherlands, you have this prestigious personal award program called "Veni, Vidi, Vici", which is aimed at excellent junior, mid-career and senior researchers.

I have coached a few, and I have been quite successful at it.

I work in one-on-one settings with the candidates, and then we find out how we can raise the bar. I coach candidates from any research field. The key is to train them to write clearly and efficiently and to make a presentation such that each slide tells a convincing story. I tell them: if you are as good as you think you are, you have to be able to win awards. For, you see, it is of no use to be bright, if no one knows about it.”