Enabling High-Performance, Large-Aperture, Multi-Terawatt Ultrafast Gratings through Semiconductor Manufacturing Processes

High-energy ultrashort laser pulse (USPL) technologies are vital for DoE accelerator applications, such as proton and ion beam manipulation and diagnostics. Diffraction gratings are essential in USPL systems for tasks like pump wavelength stabilization, spectral beam combining, pulse compression, and spatial filtering. However, existing commercial diffraction gratings have limited efficiency, causing significant power losses, especially in multi-grating pulse stretcher and compressor setups. Traditional manufacturing methods like ruling engines and holography face challenges, including high errors, limited groove shapes, and inadequate uniformity, leading to high scattering loss, lower efficiency, and restricted wavelength ranges, hindering multi-terawatt to petawatt USPL performance. This proposal aims to develop large-aperture, high-efficiency (>99%) broadband reflective gratings with high damage thresholds (>0.5 J/cm² at 1 ps or >10 J/cm² at 1 ns), utilizing advanced semiconductor manufacturing techniques. By leveraging e-beam or laser lithography, we will fabricate precise grating structures over large areas, achieving a ~20x cost reduction through nanoimprint duplication. Grating efficiency and durability will be optimized using ZEMAX and PC-Grate tools in combination with conformal sputtering coatings. Thermomechanical modeling will inform substrate selection and structural design to enable rapid heat dissipation. Additionally, we will explore integrating cooling systems, such as effusion or liquid cooling, to the grating substrate for ultra-high-power, high-repetition-rate laser applications. In Phase I, Spectral Energies (SE), in collaboration with Penn State University (PSU), will conduct a feasibility study to design, fabricate, and test small-size coupons (~25 mm x 25 mm) for 1-micron and 10-micron high-performance gratings. SE will design the grating structures and select multi-layer coating materials to achieve the desired efficiency. Optomechanical simulations will predict thermal loading when exposed to high-energy lasers, with cooling designs proposed. SE will collaborate with PSU on a manufacturing plan using semiconductor technologies. PSU will examine the grating structure and coating quality before SE evaluates efficiency. Based on results, SE and PSU will plan grating optimizations and develop Phase II plans for large-aperture, high-performance gratings. This innovation promises to significantly enhance USPL output power, expanding applications in high-energy laser industry such as laser machining, laser-driven fusion, direct-energy weapon, material testing. High-performance gratings for visible to long-wavelength IR have broad applications in optical sensors for medical, chemical, food, and agricultural analysis.