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The research activities in the group are at the intersection of optics and condensed matter physics with two main research directions. On the one hand, we employ experimental techniques to understand light matter interactions in semiconductors enriched by solid-state physics. On the other hand, we aim to exploit fundamental optical physics for proof of concept demonstrations of nonlinear optical devices, topological photonic devices and quantum photonic devices.
Exciton polaritons in microcavities
Exciton polaritons are man-made quasiparticles resulting from the strong coupling between cavity photons and semiconductor excitons. With part-light and part-matter nature, these polariton eigenstates inherit the advantages from both the excitonic and photonic parts, thus serving as a linking bridge between photonics and condensed matter. For instance, they inherit from their photonic components a low effective mass and fast propagation over long distances, while the constituent excitons provide them strong interacting nature through coulomb exchange interaction. Such advantages can lead to a rich set of exotic physics phenomena, such as Bose-Einstein condensation, superfluidity and quantum vortices, as well as optoelectronic applications, such as low threshold polariton lasers. and ultrafast polaritonic logic devices
Topological Photonics and Polaritonics
In the past decades, topological concepts, originally from mathematics, have witnessed significant advances in various systems, including condensed matter systems, photonic systems, etc. The hallmark property of nontrivial topology is the emergence of topological conducting edge states with gap opening, which are protected by the nontrivial topology of the bulk. Such topological protection allows them to remain stable against certain imperfections and disorder, which promises bright future in real world devices with low power consumption and long lifespan. Specifically, we are interested in achieving novel topological phases in photonic and polaritonic systems and exploit novel topological states for proof of concept demonstrations of optical devices, such as topological lasers, topological photonic logic devices and circuits.
Properties of energy conserving systems are ideally described by Hermitian Hamiltonians, where their eigenvalues are all real. While in real world, systems are usually non-conservative that couple to the environment with gain and losses. These systems, for example photonic and polaritonic systems, theoretically described by non-Hermitian Hamiltonians, would exhibit peculiar features with complex eigenenergies and no Hermitian counterparts. A typical example is the non-Hermitian degeneracy of Exceptional points with at least two eigenvectors and associate complex eigenvalues simultaneously coalescing. The growing understanding of such non-Hermitian physics with gain and loss allows demonstrations of novel functionalities, such as loss-induced lasing, enhanced sensing, and optical nonreciprocity.
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