Research on flexure mounts for large aperture transport mirrors of future ICF facility

Surface aberrations of transport mirrors within Inertial Confinement Fusion laser facility have significant impacts on system's optical and physical performances. Mounting design of transport mirrors is challenging for the critical specifications of mirror surface aberration under extreme operation environment. This paper presents a novel and general flexure mounting method and structure for transport mirrors with various-axis towards gravity to minimize the mirror surface aberration. Key techniques involved in mirror mounting design, including theoretical modeling, numerical optimization, optomechanical structure design and analysis, and optical testing are explored. The relationship between mirror surface aberration and its use angle θ subject to gravity is clarified using thin elastic plate theory. The mounting configuration is parametrically optimized with a more comprehensive mathematical model. Optomechanical structure design and analysis of the flexure mirror mount are detailed and accomplished. The performance of the proposed mount is experimentally validated by interferometric measurements. Experimental results indicate that the designed mirror mount potentially provides the transport mirrors (with 45° ≤ θ ≤ 90° and no screw pretension) a peak-to-valley aberration level about λ/3 (λ = 632.8 nm) of the total aberration and ∼λ/4 of the residual aberration, respectively. The proposed mounting method and structure provide a feasible and promising method and technique scheme to minimize the transport mirror surface aberrations for the next generation Inertial Confinement Fusion laser facility. The paper work also represents a design effort and a beneficial attempt for analyzing and minimizing gravity aberration for large-aperture, various-axis, and rectangular flat mirrors.