Lightweight design and performance analysis of cordierite reflective mirror

With the rapid development of astronomical observation and space optical technology, traditional materials such as silicon carbide (SiC) and microcrystalline glass face challenges due to high preparation cost, difficult processing or insufficient thermal stability. Cordierite (Mg₂Al₄Si₅O₁₈), as a ceramic material with ultra-low expansion coefficient, has excellent thermomechanical properties, low density and cost advantages, and is expected to become an alternative material for large-aperture mirrors. This paper studies the feasibility of the application of cordierite in the design and use of 300 mm aperture optical mirrors. Through the structural design and finite element simulation of the cordierite mirror primary mirror, its coefficient of thermal expansion (CTE), rigidity, lightweight design feasibility and surface accuracy root mean square (RMS) are systematically analyzed. The analysis results of the cordierite mirror are compared with those of microcrystalline glass and SiC traditional mirror materials. The results show that the average thermal expansion coefficient of cordierite from room temperature to temperature rise environment is lower than that of microcrystalline glass, and its primary mirror structure weight is better than SiC; through the lightweight structure design of the back of the primary mirror, the mirror weight can be reduced by nearly 10% compared with the SiC primary mirror; the surface error of the primary mirror can reach λ/50 (λ=632.8 nm); the first-order modal frequency of the primary mirror can reach 3506Hz, which meets the requirements of optical-grade reflective mirrors. Compared with traditional materials, cordierite shows significant advantages in cost, processing cycle and thermal stability. This study provides the experimental basis and technical reference for the application of cordierite materials in the field of optics.