Large Second-Order Nonlinear Heavy-Metal Oxide Glass Fibers

Over the last few years the growing impact of photonics on next generation technology, ranging among areas such as quantum information processing, infrared sensing, and data center photonics, has been clearly evident. Breakthrough improvements in photonics technology are fundamentally driven by advances in materials science, as initially demonstrated in the development of laser technology, and, in particular, optical fiber, which required new discoveries in the fascinating science of optical glass. New optical glasses, optical glass fabrication processes and novel optical fibers are among the major features of the National Science Foundation research program, "Large Second-Order Nonlinear Heavy-Metal Oxide Glass Fibers". The program will develop new methods for synthesizing and processing glasses that are based on tellurium oxide and bismuth oxide and then performing a special process called poling that will provide these glasses with properties that will allow them to perform technologically important functions such as shifting the optical frequency of a laser, modulating the output of a laser to create digital information that can be used for information technology, and creating light signals tailored for quantum optical networks. The project will provide rich hands-on learning opportunities for undergraduate and graduate students, as well as early-career researchers, in fiber optics, laser physics, optical materials, and advanced glass and fiber fabrication. Students will gain experience working with state-of-the-art tools and techniques, preparing them for future leadership roles in academia, industry, and national laboratories. Heavy-metal oxide (HMO) glass, defined as a glass containing significant proportions of oxides such as tellurite (TeO₂), bismuth (Bi₂O₃), lead (PbO), or tungsten (WO₃), has attracted great interest in advanced optical and photonic applications due to important properties such as high refractive index, large third-order optical nonlinearity, high density, low phonon energy, extended infrared transmission, and excellent thermal and chemical stability. However, due to their amorphous nature and centrosymmetric structure, HMO glasses inherently lack a second-order nonlinear optical nonlinearity, χ(2). This project aims to develop poled HMO-glass fibers with significantly enhanced χ(2) coefficients, enabling their use as an attractive alternative to fiber-coupled periodically poled lithium niobate (PPLN) waveguides for many applications. The research will explore and optimize various poling techniques, fabricate and characterize HMO-glass fibers, and demonstrate their capabilities in nonlinear optical processes such as second-harmonic generation (SHG), spontaneous parametric down-conversion (SPDC), and electro-optic modulation. This project advances the field of nonlinear optics by investigating second-order nonlinear phenomena in HMO-glass fibers, an area that remains underexplored compared to silica or crystalline materials. By leveraging poling techniques to establish a χ(2) nonlinearity in fibers with inherently superior optical properties, this research addresses critical challenges in nonlinear optical material development, including understanding of charge transport processes, dipole orientation, and the long-term stability of the poled response. Through systematic exploration of thermal and laser-based poling approaches, the project will optimize χ(2) in HMO glasses and fibers, enabling high-efficiency nonlinear interactions such as SHG, SPDC, and electro-optic modulation. Comparative studies of different glass compositions will provide fundamental insights into the relationships between glass structure, composition, and nonlinear optical response. The research outcomes will not only expand our understanding of nonlinear optical mechanisms in amorphous systems but also enable new fiber-based platforms with advantages in compactness, integration, and efficiency. 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.