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Doctoral defence of Sughra Mohamed, MSc, 9.12.2022: Confinement and tailoring of light in plasmonic and photonic crystals

The doctoral dissertation in the field of Physics will be examined at the Faculty of Science and Forestry, Joensuu Campus.

What is the topic of your doctoral research? Why is it important to study the topic?

The topic of my doctoral research is the controlling, confinement, and tailoring of light in nanostructures, particularly in plasmonic and photonic crystal systems. It is important to be able to tailor the light field to obtain the desired output and meet the requirement for specific applications.

What are the key findings or observations of your doctoral research?

This research highlights a number of different methods and techniques for achieving strong field confinement by plasmon-exciton coupling, bound states in continuum, and dark state outcoupling. The main scientific achievements of the thesis include: 1) Active tuning of interaction between the surface plasmon mode and photochromic molecules with optically induced crossover from weak to strong coupling regimes; 2) Demonstration of lasing action from multiple bound states in continuum with the associated topological charges, and 3) Realization of lasing in dark resonant states of a metasurface through controllable outcoupling using scattering technique.

How can the results of your doctoral research be utilised in practice?

Optics and photonics play an important part and are integral to modern science and technology, including communications, and imaging. Since the role of these fields is continually growing, the development of new technologies to control the state of light is an integral part of the process. Plasmonics and photonic crystals have interesting optical properties with many potential applications including the engineering of 2D lasers, and effective coupling out the light from nanostructures.

What are the key research methods and materials used in your doctoral research?

The thesis provides a thorough analysis of the collected data and discusses the obtained results in the broader context of the recent developments in the fields of nanophotonics and plasmonics. In this work, various phenomena related to the interaction of light and matter are confined to nanoscale regions and the emission of light from them, including surface plasmon polariton, polarization, photonic crystal, bound state in continuum, dark and bright state. I was able to observe these phenomena not only experimentally, but also analyze them in detail and reproduce the experimental results using computational methods.

The doctoral dissertation of Sughra Mohamed, MSc, entitled Confinement and tailoring of light in Plasmonic and Photonic crystals will be examined at the Faculty of Science and Forestry. The opponent will be Professor Peter G. Kazansky, University of Southampton, and the custos will be Professor Tommi Hakala, University of Eastern Finland. Language of the public defence is English.

For more information, please contact:

Sughra Mohamed,

Dissertation book online