Periodic Reporting for period 2 - QUANTUM LOOP (Quantum Light Spectroscopy of Polariton Lasers)
Reporting period: 2018-10-01 to 2019-09-30
Coherent nonlinear optical spectroscopies were employed on a variety of hybrid organic inorganic perovskites to obtain a comprehensive perspective on the nature and dynamics of excitons particularly in lower dimensional derivatives that host two-dimensional excitations. We have provided evidence for the ubiquitous role of the crystal vibrations in the excitonic characteristics and proposed exciton polaron model in these material systems. We also identified 2D perovskite architectures to create polariton lasers and embedded them within high quality microcavities. We have also developed theoretical and experimental tools based on entangled photon pairs to estimate many-body correlations in excitonic systems, which will be further developed in the future as alternative material probes.
(a) A quantitative analysis of the optical absorption, supported by coherent non-linear dynamics that established the presence of multiple excitons in a variety of 2D perovskites. (Physical Review Materials 2, 064605 (2018));
(b) Resonant impulsive stimulated Raman scattering that demonstrated that each of these excitons are dressed by distinct vibrations of the lattice. (Nature Materials 18, 349 (2019));
(c) Photon-echo measurements that identified and quantified the interaction of the excitons with each other and more importantly highlighted the presence of a protection mechanism from the crystal vibrations that reduces the probability of loss of photo-generated excitons ( Physical Review Research, 1, 032032);
(d) When two excitons overcome such a protection barrier, they form a new particle called biexciton, where they lose their individual behavior and behave as one particle. Their presence in 2D perovskites was demonstrated in Physical Review Materials 2, 034001 (2018).
(e) The relaxation process of the excitons which leads to production of light is controlled by the crystal vibrations and thus the design of appropriate crystal structure is crucial in increasing the material efficiency for light emission. (Chemistry of Materials 31, 7085 (2019)).
Specific two-dimensional perovskite architectures were identified to have ideal characteristics to be incorporated in polariton devices. Strongly coupled microcavties with 2D perovskites were fabricated and characterized to demonstrate polariton formation.
In order to address the second set of objectives, sources of entangled-photon pairs were developed and characterized by quantum-optical tomographic techniques. Experimental schemes to employ such methods for material spectroscopy were also implemented. Independently, theoretical framework to deal with quantum spectroscopies was developed in close collaboration with Prof. Bittner (University of Houston). These theoretical investigations also enabled optimization of the experimental methodologies. As a proof of concept, intermediates of singlet fission process in molecular aggregates have been probed with entangled photons to demonstrate their efficacy in probing excitonic correlations.
The experimental and theoretical tools for quantum spectroscopy developed within this project can potentially lead to a completely novel perspective in material spectroscopy and in the treatment of light-matter interactions. Apart from offering unambiguous probes of matter correlations, these investigations may inspire methodologies to use matter to manipulate photon-entanglement, which is at the heart of a quantum-optical logic gate.