Defence of doctoral thesis in the field of Advanced materials and photonics, M.Sc. Yadong Wang

M.Sc. Yadong Wang will defend the thesis "Transient Nonlinear Optics of Two-Dimensional Layered Materials" on 4 March 2022 at 12:15 in Aalto University School of Electrical Engineering, Department of Electronics and Nanoengineering.

Opponent: Prof. Nathalie Vermeulen, Vrije Universiteit Brussel, Belgium
Custos: Prof. Zhipei Sun, Aalto University School of Electrical Engineering, Department of Electronics and Nanoengineering

The public defense will be organized via remote technology. Follow defence: https://aalto.zoom.us/j/64945801659
Zoom Quick Guide: https://www.aalto.fi/en/services/zoom-quick-guide

Thesis available for public display at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/
Doctoral theses in the School of Electrical Engineering: https://aaltodoc.aalto.fi/handle/123456789/53

Press release:

Since the first reported second-harmonic generation (SHG) in 1961 (Phys. Rev. Lett. 1961, 7, (4), 118-119), harmonic generations (HGs) play an increasingly important role in various technologies, especially in our modern information society. These nonlinear optical processes have been widely exploited for various important applications, such as coherent light generation, crystalline characterization, bio-imaging, and spectroscopy. However, nonlinear optical effects normally have relatively low efficiency to be controlled, especially for the high-order harmonic generation (HHG). Therefore, reinforcing and controlling the efficiency of HGs are of importance for numerous applications of nonlinear optics.

The recent discovery and development of two-dimensional (2D) materials offer promising opportunities for actively engineered nonlinear optics in nanophotonics and nanoelectronics. Indeed, 2D materials such as graphene, transition metal dichalcogenides (TMDs) have shown excellent linear and nonlinear optical properties within atomic thickness, which are highly tunable.

This thesis studies the transient linear and nonlinear optical processes in 2D materials, offering a way to control and enhance nonlinear optical responses. All-optical modulations of nonlinear optical responses have been achieved with high modulation depth up to 90% and ultrafast speed of ~600 fs. Our results have revealed that the HGs including SHG, third-harmonic generation and HHG are highly sensitive to the oscillation strength of bright and dark exciton states, indicating that 2D materials are promising to active nonlinear optical applications. Meanwhile, broadband static and transient nonlinear optical processes have been established to probe the bright and dark excitons states in 2D materials, offering a potential platform for the characterization of monolayer semiconductors and their heterostructures.

Contact information of doctoral student