A Route to Pure Optical Rotation through Nano-Engineered Chirality

Non-technical Description Polarization is a property of light that describes how electromagnetic fields oscillate as light travels through space. Controlling the polarization of light without losing signal strength is essential for next-generation optical technologies. These include high-speed, secure communications and photonic quantum computing. This project develops a new class of materials towards achieving “pure optical rotation” in which light changes its polarization orientation without loss. A central advantage of this approach is using self-assembly to build nanostructures instead of conventional fabrication methods. The research thereby establishes a scalable and low-cost approach for modern photonic systems. Training of graduate and undergraduate students is integral to the project. In turn, this prepares a technologically skilled domestic workforce with expertise in quantum materials and photonics. Broader engagement includes demonstrations of optical phenomena to strengthen the public understanding of light–matter interactions and their importance to modern technologies. Technical Description The research investigates how to generate strong circular birefringence, defined as a difference in refractive index for left- and right-circularly polarized light, while suppressing circular dichroism, which causes optical loss. The central scientific problem is whether non-degenerate exciton coupling in ordered nanomaterial assemblies can decouple optical rotation from absorption. The project develops and validates a quantum mechanical coupled-dipole framework that connects nanoscale transition dipole geometry, energetic detuning, and structural disorder to macroscopic chiroptical response. Guided by this framework, experimental efforts implement these principles of non-degenerate coupling in two materials systems: oriented organic multilayers and semiconductor nanomaterial superlattices, constructed with controlled stacking and excitonic energy offsets. Optical measurements, including absorption, circular dichroism, and polarimetric analysis, quantify low-loss optical rotation and validate theoretical predictions. By establishing quantitative structure–property relationships, the research advances the fundamental understanding and design of excitonic photonic materials with independently controlled phase and absorption. 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.