Experimental demonstration of ozone gratings created by interfering ultraviolet lasers*

The final optics in a laser-driven inertial fusion energy (IFE) plant would face significant neutron, x-ray, and debris fluxes from the target for extended periods of continuous operation. Manufacturing optics that can properly operate while enduring this harsh environment is a non-trivial challenge. To address this issue, we can create optics in gas by using interfering ultraviolet lasers to induce substantial density modulations in an ozone-oxygen mixture via periodically heating the gas in space. The spatially modulated gas will then act as a volume diffraction grating. These transient optics are debris-resistant and feature much higher damage thresholds than traditional solid-state optics, providing a promising method towards efficiently manipulating high-energy laser beams. In this work, we created an ozone grating experimentally using the 4th harmonic of an Nd:YAG laser. We demonstrated the efficient diffraction of a nanosecond probe beam by a gas grating and characterized several key properties of the system, including its lifetime and the impact of energy deposition on the temporal evolution of the gas response. The experimental results support a theoretical model of the process that includes the heat deposition mechanism, gas dynamics, and the resultant optical response, suggesting parameters that allow the efficient creation of gas gratings.