EAGER: Exploring Extreme THz Photonics with Quantum Fluids

Part 1. Nontechnical Description Terahertz (THz) radiation lies between microwaves and infrared light in the electromagnetic spectrum and has unique capabilities for probing the structure and properties of materials without causing damage. Over the past three decades, advances in THz technology have enabled important applications in materials characterization, biomedical imaging, chemical sensing, security screening, and ultrafast science. The next major challenge is to generate much stronger THz pulses that can manipulate matter in entirely new ways rather than simply observe it. This project explores new approaches for producing and measuring extremely intense THz radiation and for understanding how light interacts with matter under extreme conditions. The research will investigate innovative materials and media, including quantum fluids such as liquid and superfluid helium, which possess unique physical properties that may enable previously inaccessible optical phenomena. The knowledge gained will expand the scientific foundation of THz photonics and may ultimately contribute to future technologies in advanced imaging, sensing, communications, and quantum science. The project will provide interdisciplinary training for graduate and undergraduate students in ultrafast optics, laser science, cryogenics, and plasma physics. Students will gain experience with state-of-the-art experimental techniques and advanced instrumentation, helping prepare the next generation of scientists and engineers in photonics and quantum technologies. By advancing fundamental knowledge while developing a highly skilled workforce, the project supports the National Science Foundation's mission to promote the progress of science and advance the nation's health, prosperity, welfare, and security. Part 2. Technical Description Intellectual Merit This project investigates extreme THz photonics through two complementary research thrusts. The first develops single-shot diagnostic techniques for characterizing ultra-intense broadband THz pulses generated by high-energy ultrashort laser systems. Building upon recent demonstrations of joule-level THz pulse emission from laser-driven microplasmas, the research will employ kilojoule-class laser facilities to investigate a broad range of THz-generating targets and establish the scaling laws governing high-field THz generation. The second thrust explores strong-field laser interactions with liquids, particularly superfluid helium, a quantum fluid exhibiting macroscopic quantum coherence and near-zero viscosity. By measuring THz emission and nonlinear optical responses in both normal liquid and superfluid phases, the project will determine how quantum coherence and reduced dissipation influence plasma formation, energy transport, nonlinear optical processes, and THz generation. The results are expected to reveal new mechanisms of light-matter interaction and establish cryogenic quantum liquids as a new platform for extreme THz photonics. Broader Impacts The project introduces quantum fluids as a new class of media for high-field THz generation and nonlinear optics, potentially enabling future advances in THz sources, ultrafast spectroscopy, and photonic technologies. It will provide interdisciplinary research opportunities for graduate and undergraduate students through hands-on training in ultrafast optics, cryogenic systems, plasma physics, and advanced instrumentation. The project will contribute to workforce development in photonics and quantum science while broadening the scientific understanding of extreme light-matter interactions. 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.