By using light waves to create high-resolution, three-dimensional images of the internal structure and function of biological tissues, OCT can provide valuable information for diagnosis, treatment, and monitoring of various diseases and conditions.
However, OCT also faces some challenges and limitations, such as the availability and quality of light sources that can operate at different wavelength ranges and offer broad spectral bandwidths. These features are essential for achieving high resolution, contrast, and penetration depth in OCT imaging.
To address these challenges, the innovative training network (ITN) called the Next generation of tunable sources for OCT(NETLAS) has been established. As a part of this network, Philipp Tatar-Mathes has developed novel membrane-based semiconductor lasers that can overcome some of the drawbacks of conventional edge-emitting laser devices. The so-called membrane external-cavity surface-emitting lasers (MECSELs), are thin gain membranes that can be transferred and integrated on various substrates, such as silicon or glass.
“This allows for high flexibility, combined with scalability in the design and fabrication of MECSELs,” says Tatar-Mathes.
In his thesis, he demonstrated several MECSELs that can operate at difficult wavelength ranges, such as red, which is important for imaging blood vessels and oxygen saturation. He also showed that MECSELs can achieve broad spectral tuning and laid out a foundation that enables the designs of even broader structures in the future, which is crucial for enhancing the axial resolution and contrast in OCT imaging.
During his mobility part granted by the NETLAS ITN, Tatar-Mathes explored the potential of an all-fiber based polarization-sensitive OCT (PS-OCT), a functional extension to OCT capable of retrieving the birefringence of a sample of interest. Together with international collaborators and a setup based in Kent University, UK, he investigated effects related to the temperature-dependent properties of a PS-OCT system.
In his doctoral dissertation, Tatar-Mathes also presented a novel approach to achieve super-luminescence operation based on the membrane emitting platform.
“This research encourages new possibilities for improving the performance and versatility of OCT technology for biomedical applications. We have demonstrated that MECSELs can offer unique advantages over conventional light sources in terms of wavelength range, spectral bandwidth, tuning capability, and integration potential. We hope that our work will inspire further development and innovation in this field,” he explains.
More information about this research can be found on the website of the Optoelectronics Research Centre at Tampere University.
Public defence on 16 November
The doctoral dissertation of M.Sc. Philipp Tatar-Mathes in the field of photonics titled Membrane-based broadband semiconductor light sources for optical coherence tomography will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at 13:00 on thursday 16.11.2023 at Hervanta campus, in Festia building in Pieni Sali 2 (Korkeakoulunkatu 8, Tampere). The Opponent will be Doctor Sami Suihkonen from Aalto University. The Custos will be Professor Mircea Guina from Tampere University.
The doctoral dissertation is available online.
The public defence can be followed via remote connection.
Photo: Prabudeva Ramu