Optical and Quantum Coherence Study of 2D-Material Based Cavity-Enhanced Emitters and Nanolasers

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The proposed research aims at the understanding of a series of fundamental physics questions related to a) the emerging monolayer semiconductor transition metal dichalcogenides, b) quantum optical properties of light emission from nanoemitters and nanolasers, as well as c) important device physics issues of nanolasers based on such monolayer semiconductors. We will address the suitability of the new active-material platform and promising material choices, the demonstration of laser action in terms of quantum-optical emission properties, and device realizations with improved outcoupling efficiencies. The integrated system of monolayer semiconductors with nanocavities provides an ideal state-of-the-art platform for the proposed study. The team consists of three well qualified, highly complementary groups specializing in microscopic theory of 2D semiconductors interacting with quantized light field (Jahnke group, University of Bremen), fabrication, and characterization of nanolasers (Ning group, Tsinghua University), and quantum optical coherence study of light emission (Reitzenstein group Technische Universität Berlin), respectively. The well-knit Sino-German team is uniquely suited to investigate the important questions raised above in the most comprehensive and integrative manner through an iterative cycle from materials preparation, device fabrication, experimental characterization, and first-principle theoretical prediction and interpretation. From the fundamental science point of view, the expected results can potentially impact our basic understanding of light emission and gain mechanism in 2D monolayer semiconductors, as well as the nature of quantum coherence of nanoemitters, especially the relationship between threshold behavior of the nanolasers and quantum coherence. In this context, we will address the important issue of how to verify laser action in nanocavity lasers with spontaneous emission coupling factors (beta-factor) approaching unity close to the limiting case of a thresholdless laser. This fundamental regime of semiconductor lasers will be explored by comprehensive quantum optical studies on the photon statistics of emission, acting as the most sensitive tool to unambiguously identify the onset of coherent light emission. The joint experimental and theoretical work will aim at a new level of understanding the emission processes of nanolaser by considering the photon-number distribution of emission in addition to input-output and linewidth dependencies. Here, the photon-number distribution gives access to the full photon statistic including higher order photon correlations. This work will be enabled by highly advanced photon-number resolving detectors in the Reitzenstein group. From the technological point of view, the proposed research could lead to a new type of nanophotonic devices for applications in next generation of information technologies, or novel devices in quantum information technologies.