Advanced Manufacturing of High-performance Broadband Graded-index THz Anti-Reflection Coatings

The rising demand for high-performance components in terahertz (THz) applications has resulted in a compelling need for advanced anti-reflective (AR) coatings that can minimize or eliminate reflections across broad ranges of the THz band. Conventional AR coatings frequently fall short in the THz spectrum leading to reflection losses and inefficient optics. This is particularly critical for the Cosmic Microwave Background (CMB) instrumentation testbed system and the CMB-S4 telescopes, and industries such as healthcare, material science, homeland security, and defense where the amount of THz power delivered in the system directly impact the speed and accuracy of THz-based systems. We propose a new method for creating the features required for THz graded-index AR coatings using advanced femtosecond laser fabrication techniques. This method will allow rapid, economical, large area fabrication of graded-index AR coatings for THz optics for a broad range of materials that includes hard ceramics and thermoplastic polymers. In the proposed Phase I feasibility study, we will perform simulations and fabrication experiments with both hard, high refractive index, high melting temperature ceramic materials as well as softer thermoplastics with lower refractive indices and melting temperatures. Demonstrations in these two classes of materials will show the applicability of the proposed technology to a wide range of materials. We will also perform simulations and fabrication experiments on graded-index anti-reflection coatings designed for frequencies from 20 GHz up to 20 THz, covering a full range including CMB frequencies, THz radiation, and mid- to farinfrared light. This will demonstrate the wide range of the mm-wave/THz/infrared spectrum that the proposed AR coating technology can address. If successful, the proposed work will provide a significant advancement in the performance of a broad range of optics for THz to long-wave infrared radiation, including optical windows, refractive lenses, filters, polarizers, non-linear THz generation crystals, beamsplitters, and more. Applications include astrophysics areas such as cosmic microwave background (CMB) experiments, THz imaging for defense and homeland security, biomedical imaging, THz spectroscopy, and quality control in manufacturing. Potential future applications in next-generation wireless networks frequencies in the THz range have been proposed for high data rate “6G” networks. In a future potential Phase II project, we will develop a prototype tool to address the THz AR coating the needs of the THz R&D and industrial community.