MESA+ University of Twente
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Fehmi Çivitci

Integrated optical modules for miniature raman spectroscopy devices.

Promotion date: October 31.

Promotor: Prof. Dr. Markus Pollnau

Assistant Promotor: Dr. Hugo J.W.M. Hoekstra

Raman spectroscopy is a powerful materials analysis technique used for identification of molecules residing near the surface of a sample. It has been successfully used for a broad range of application areas such as material science, biology, medicine and pharmacology, owing to its numerous advantages.

A traditional Raman measurement system is a complex setup, whose usage is limited due to its bulky and expensive components. If it would be possible to achieve a miniature Raman spectroscopic system with affordable costs by using integrated optics and electronics technology, it could be utilized further in the aforementioned applications.

The goal of this PhD study was to realize small-scale optical components, which could function as building blocks of a hand-held Raman measurement system, by using integrated optics. For this purpose, three different integrated optical modules in the SiON material platform are proposed in this thesis: out of plane light turning mirrors, prism spectrometers and polarization splitters.

What was the main objective of you thesis work?

The ultimate aim is to fabricate a handheld Raman Spectrometer by using Integrated Optics and Integrated Electronics. We made a hybrid electro-optical device - which we call: sugar cube size device - as an intermediate result. I mainly worked on the design and fabrication of optical chips. We implemented some necessary functionalities in the optical chip such as: spectrometers, polarization splitters and light turning mirrors.

In the project two groups were involved: Integrated Optical Microsystems and Integrated Circuit Design, and it was named OptoLip: Optical Lab-in-a-package. It was supported by STW. The fabrication and characterization processes were from scratch. Along the way we defined our research goals and problem solving strategies. This was a tough but fascinating journey to undertake.

Can you recall some special moments during your PhD period?

I can recall a good one and a bad one, in fact. During the transition period of the NanoLab I designed the polarization splitter by making good use of theory and literature. Returning into the lab, the first device that I fabricated functioned very well, right from the start. So, one could say I made good use of the waiting period by working efficiently.

The other moment was two months before the end of my project. By that time I was doing the fabrication of a new design and came up with two wafers - one was dummy and the other one was the real process wafer - until the last process step, which was Deep Reactive-ion Etching (DRIE). First, I tried the process on the dummy wafer and then I did the process on my process wafer. During the processing of the real wafer something went wrong and the wafer was broken into pieces. As a result, I had to start a new fabrication process. This set-back took me some nights of bad sleep.

In what respect did you develop as a scientist and researcher in this four years time.

During my master work I was working mostly on my own. This changed radically during my PhD work in which I collaborated with many colleagues; different group members and technicians from the NanoLab as well as from the Integrated Optical Microsystems labs. My attitude changed. I found out it is far less favorable to find out all aspects on your own while the expertise requisite is at hand. By doing so, progress is faster and you contribute to your personal development more.

Apart from learning various skills, I also built up lots of experience: how to use various kinds of equipment in the cleanroom and how to set up optical experiments from scratch.

What are your future plans?

At the moment I work as a post-doc at the KOÇ University in Istanbul. I joined a team that is already strong in optical research. The group is working on an ERC Advanced Grant project concerning wearable displays for 3D vision applications in a new way.

In future I strive for a position as an assistant professor, perhaps first spending some years in industry. I expect to learn from commercial processes, working towards products being used in daily practice.

In Turkey some university groups are working in a modern way already, and I am lucky to be part of one of them right now. Many projects are undertaken in collaboration with industry and spin-off companies. I like the atmosphere in which research goals are aimed towards practical use as well as to publishing papers. I hope to implement this approach in future research strategies.

In what journals did you manage to publish your results?

Articles were published in Optics Express and in Optical and Quantum Electronics.

What, in your opinion, is important for Mesa+ to stay successful in future?

During my PhD some changes took place in the organization of the research group I was involved in. By managing and guiding these processes in a better way, the PhD’s and researchers remain motivated to perform well in high standard research. The equipment and staff expertise could be better deployed in these transition periods.