The doctoral dissertation in the field of Photonics will be examined at the Faculty of Science, Forestry and Technology, Joensuu campus and online.
What is the topic of your doctoral research? Why is it important to study the topic?
My doctoral research focuses on developing integrated photonic devices for compact, high-resolution LiDAR (Light Detection and Ranging) systems directly fabricated on silicon chips. The study addresses the growing demand for fast, precise, and miniaturised optical sensors for autonomous vehicles, robotics, and environmental mapping. Integrating LiDAR functions on a photonic chip drastically reduces size, cost, and energy consumption compared to bulky mechanical systems, paving the way for scalable, reliable sensing in future smart technologies.
What are the key findings or observations of your doctoral research?
The research demonstrates edge-coupled optical phased arrays (OPAs) integrated with custom 3D-printed collimating lenses, achieving significantly reduced beam divergence and extended Rayleigh range. It introduces wavelength-tuned 512-channel OPAs capable of steering optical beams and implementing frequency-modulated continuous-wave (FMCW) distance measurements with centimeter accuracy. A novel SiGe-based grating out-coupler was designed, reaching 75 % theoretical coupling efficiency. Together, these advances establish a foundation for compact, high-performance on-chip LiDAR systems.
How can the results of your doctoral research be utilised in practice?
The developed photonic structures can be applied to miniaturised LiDAR sensors for autonomous vehicles, drones, and robotics, enhancing spatial awareness and safety. The 3D-printed lens approach enables cost-efficient optical packaging adaptable to various beam-steering applications. Additionally, the SiGe-based out-coupler design improves efficiency in optical communication and free-space sensing devices, supporting future integration of photonics with CMOS electronics.
What are the key research methods and materials used in your doctoral research?
The work combined simulation, design, and experimental characterisation on VTT’s 3 µm silicon-on-insulator photonics platform. Optical phased arrays, grating couplers, and 3D-printed lenses were designed using FDTD and finite-difference mode solvers. Fabrication employed stepper lithography, ICP-RIE etching, and PECVD cladding deposition. Beam-steering and distance-measurement experiments were conducted using tunable lasers, optical detectors, and Gaussian beam analysis. The study integrates theoretical modelling with practical prototyping to realise efficient chip-scale LiDAR components.
The doctoral dissertation of Sidra Tul Muntaha, MSc, entitled Development of Integrated Photonics for On-Chip LiDARs will be examined at the Faculty of Science, Forestry and Technology, Joensuu campus and online. The opponent will be Associate Professor Eugenio Fazio, Sapienza University of Rome, Italy and the custos will be Professor Matthieu Roussey, University of Eastern Finland. Language of the public defence is English.
