ERI: Development of light-emitting devices having intensive quantum-optical properties using a low-dimensional semiconducting material

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The last few decades have seen significant technological advances in fabricating nanometer-scale structures and performing ultrafast laser spectroscopies. Physical or chemical phenomena occurring in extremely small distances (less than one micrometer) for extremely short time durations (less than one nanosecond) can be analyzed and understood with such advanced nanofabrication tools and methodologies. Superfluorescence (SF), collective light generations from an ensemble of interacting emitters in a nanometer-sized dimension, is one of the fascinating quantum phenomena. SF occurs when the light emitters synchronously behave under a single-mode electromagnetic field as they generate intensive short pulses. As a new type of bright light source, SF may find rich applications in quantum sensing, ultranarrow laser, and photonic-based quantum computation. The realization of SF, however, is challenging because it usually requires very low temperatures and stringent excitation conditions. This project uses a low-dimensional compound semiconductor called quasi-two-dimensional (2D) perovskites in thin film form. Indeed, a room-temperature SF has been observed in quasi-2D perovskite thin films, demonstrating that a room-temperature SF is feasible, but still, the quantum-optical properties of this SF akin to traditional SFs of gaseous phases have yet to be explored. Because of the potential inherent in a room temperature SF, it is of pressing importance that SFs from solid-state quasi-2D perovskites are refined and their exquisite quantum states measured. The proposed work will advance our understanding of the collective optical effects from a robust solid-state material and show the practical way to engineer and control the output properties of the quantum lights. This proposal aims to develop optical devices that control SF-lasing phase transitions by incorporating quasi-2D perovskite onto distributed feedback (DFB) resonators. Engineering monolithic resonant cavities with quasi-2D perovskites will provide optical controllability over the phase diagrams of SF-lasing transitions. Besides reproducing the existing results, the proposed project will perform (1) time-resolved photoluminescence spectroscopy on a femtosecond time scale to examine the dynamical characteristics of the SF emission from quasi-2D perovskite DFB resonators. This experiment will measure the SF build-up time required for the phase-synchronization of interacting emitters and the characteristic Rabi-type oscillations of photoluminescence decay curves, implying a strong light-matter coupling. Moreover, this project will perform (2) measurements of wavelength-dependent second-order correlation functions that will reveal the photon statistics and bunching characteristics of SFs. Finally, using homodyne detection tomography, the research team will (3) search for their non-classical photon states, such as displaced squeezed states. The pulsed and quantum nature of SF at room temperature may open a route toward realizing an ultrafast quantum light source. Photonic device fabrication and femtosecond time-resolved spectroscopy are the major experimental tasks of the project, which will also allow the exploitation of other emerging photoluminescent materials beyond perovskites. In addition, this project involves the development of a quantum optics lab course at Michigan Tech.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.