Theory of functional photonic structures

Enabled by the present project, a new professorship “Theory of Functional Photonic Structures” was installed in the Physics Department of Paderborn University. The new group’s research activities lie in the field of theoretical condensed matter physics and optics and complement and further strengthen the university’s research focus on Optoelectronics & Photonics. The local activities in this area are coordinated under the roof of the central research facility Center for Optoelectronics and Photonics Paderborn (CeOPP). Besides the present project, the group’s research was and is further supported by the collaborative research center TRR142 “Tailored nonlinear photonics” and the research training group GRK1464 as well as by further individual project grants and the Paderborn Center for Parallel Computing (PC2 ). Presently, the group persues a relatively broad research agenda with numerous fruitful local, national, and international collaborations. Key areas supported by the present Heisenberg grant are (i) single- and two-photon excitations in semiconductor quantum dots, (ii) nonlinear polariton physics in semiconductor microcavities, and (iii) photoexcitations and excitation dynamics in organic semiconductors and conjugated molecules. A general overview of the work done over the course of the project including a number of research highlights can be found in the selection of journal publications [P01-P10]. In addition to the journal articles published, numerous BSc and MSc thesis projects were successfully completed in the context of the present project and five PhD theses completed over the course of the project. In the present project, on the one hand we used light as a probing tool to understand the complex fundamental physics and optical properties of different (semiconductor) nanostructures. Whereas in the linear optical regime the systems’ reponse is only passively observed or probed with light, in the nonlinear optical regime the response generally depends on the optical excitation. As a consequence, in the latter case the ultrafast optical system response can be actively probed spectroscopically and specific questions can be addressed and answered systematically by varying excitation parameters such as laser pulse frequency, intensity, pulse duration, and delays. In conjuction with the (simplified) theoretical models developed and applied in the present project a detailed understanding of the microscopic mechanisms underlying the system behavior can then be obtained. Another important aspect of the present project was the exploration of novel active optical approaches to efficiently control light with light for example in all-optical switching operations in which one light signal is manipulated by another light signal and changed, e.g., in its amplitude, in its direction of propagation, or in its polarization state. In this context, beyond serving as our probe to better understand the fundamental properties of nanostructured materials, in the present project light was also used to utilize novel approaches in all-optical information processing in systems and parameter ranges in which the optical response is dominated by optical nonlinearities. Over the course of the present project we have derived, studied, implemented, and applied various different theoretical approaches to relate the microscopic many-particle physics in complex optically excited nanostructures in photonic environment to their macroscopic behavior. Theoretical approaches and methods used include many-particle density matrix theories in various approximations, electronic structure methods including density functional theory (DFT), timedependent DFT, wave-function based methods, and non-adiabatic ab-inito molecular dynamics. Many of our theoretical studies were performed in close collaboration with our experimental partners. Project results span the full range from fundamental physical aspects to the realization of novel application oriented structures and concepts for functional and active optical components. A small selection of key results include the proposal for an optically controlled and tunable deterministic semiconductor quantum dot source of single photons [P09], the realization of ultrafast optical control and switching of an optical bit in a planar semiconductor nanostructure [P01], the optical control of the optical spin-Hall effect [P08], and detailed microscopic insights into molecular doping mechanisms [P02, P10] and ultrafast excitation energy transfer [P07] in organic semiconductors and chromophores.

Project-related publications (selection)

A quantum dot single-photon source with on-the-fly all-optical polarization control and timed emission. Nature Communications, Vol. 6. 2015, Article number: 8473.

D. Heinze, D. Breddermann, A. Zrenner, and S. Schumacher

(See online at https://doi.org/10.1038/ncomms9473)

How intermolecular geometrical disorder affects the doping of donor-acceptor conjugated copolymers. Nature Communications, Vol. 6. 2015, Article number: 6460.

D. Di Nuzzo, C. Fontanesi, R. Jones, S. Allard, U. Scherf, E. von Hauff, S. Schumacher, and E. Da Como

(See online at https://doi.org/10.1038/ncomms7460)

Controlling the optical spin Hall effect with light. Applied Physics Letters, Vol. 110. 2017, Issue 6, 061108.

O. Lafont, M. H. Luk, P. Lewandowski, N. H. Kwong, P. T. Leung, E. Galopin, A. Lemaitre, J. Tignon, S. Schumacher, E. Baudin, and R. Binder

(See online at https://doi.org/10.1063/1.4975681)

Creation and manipulation of stable dark solitons and vortices in microcavity polariton condensates. Physical Review Letters, Vol. 118. 2017, Issue 15, 157401.

X. Ma, O. Egorov, and S. Schumacher

(See online at https://doi.org/10.1103/PhysRevLett.118.157401)

Ultrafast electronic energy transfer in an orthogonal molecular dyad. Journal of Physical Chemistry Letters, Vol. 8. 2017, Issue 5, pp. 1086–1092.

C. Wiebeler, F. Plasser, G. J. Hedley, A. Ruseckas, I. D. W. Samuel, and S. Schumacher

(See online at https://doi.org/10.1021/acs.jpclett.7b00089)

Microscopic theory of cavity-enhanced single-photon emission from optical two-photon Raman processes. Physical Review B, Vol. 97. 2018, Issue 12, 125303.

D. Breddermann, T. Praschan, D. Heinze, R. Binder, and S. Schumacher

(See online at https://doi.org/10.1103/PhysRevB.97.125303)

Vortex multistability and Bessel vortices in polariton condensates. Physical Review Letters, Vol. 121. 2018, Issue 22, 227404.

X. Ma and S. Schumacher

(See online at https://doi.org/10.1103/PhysRevLett.121.227404)

Externally controlled Lotka Volterra dynamics in a linearly polarized polariton fluid. Physical Review E, Vol. 101. 2020, Issue 1, 012207.

M. Pukrop and S. Schumacher

(See online at https://doi.org/10.1103/PhysRevE.101.012207)

Molecular doping in few-molecule polymer-dopant complexes shows reduced Coulomb binding. Journal of Materials Chemistry C, Vol. 8, Issue 34, pp. 11929-11935.

C. Dong and S. Schumacher,

(See online at https://doi.org/10.1039/D0TC02185G)

Realization of all-optical vortex switching in exciton-polariton condensates. Nature Communications, Vol. 11. 2020, Article number: 897.

X. Ma, B. Berger, M. Assmann, R. Driben, T. Meier, C. Schneider, S. H?fling, and S. Schumacher

(See online at https://doi.org/10.1038/s41467-020-14702-5)