Coherent Infrared Emission from Colloidal Quantum Wells

With the support of the Macromolecular, Supramolecular and Nanochemistry (MSN) Program in the Division of Chemistry, Professor Liangfeng Sun and his group at the Bowling Green State University are developing tiny sheet-like materials (called nanosheets) that can emit highly controlled light. These materials are designed so that the thickness controls the “color” of light they emit, while their large area allows for multiple light particles (photons) to work together in a coordinated way - key for future quantum technologies. Their work focuses on creating and studying these nanosheets to produce coherent photons in the near-infrared range, which is useful for secure quantum communication through existing fiber-optic networks. The project also supports education at multiple levels: undergraduate and graduate students gain hands-on experience in cutting-edge science, high school students participate through summer research, and outreach efforts extend to the Dayton, Ohio area to engage with local universities and high-tech labs, including the Air Force Research Lab. This collaboration aims to help build a strong future workforce in quantum science and technology. The research team will: (1) investigate amplified spontaneous emission, giant oscillator strength transitions, and superfluorescence in colloidal PbS nanosheets; (2) examine the effects of surface states, Auger recombination, and exciton funneling on optical properties; and (3) explore how trions, polarons, and exciton localization impact coherent emission. A wet-chemistry approach will be used to synthesize and modify colloidal quantum wells. The crystal structure of the nanosheets will be determined through high-resolution transmission electron microscopy and X-ray diffraction, while time-resolved laser spectroscopies, such as time-resolved fluorescence and transient absorption spectroscopy, will be used to study exciton coherence properties. The effects of surface states, trions, and polarons will be further investigated with additional experimental methods, including optical second-harmonic generation, electrogenerated chemiluminescence spectroscopy, and Raman spectroscopy. 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.