Manufacturing aspheric mirrors made of zero thermal expansion cordierite ceramics using Magnetorheological Finishing (MRF)

Stable CW laser based on low thermal expansion ceramic cavity with 49 mHz/s frequency drift

“…Hereinafter, a reference cavity based on this thermal expansion ceramic will be referred to as a "ceramic cavity". NEXCERA is a cordierite (2MgO-2Al2O3-5SiO2), which has a polycrystalline structure with a 1μm grain size and an amorphous layer between grains [15]. NEXCERA has a Young's modulus of approximately 130 GPa and a Poisson's ratio of approximately 0.30, which means high specific rigidity, compared to ULE that has the Young's modulus of approximately 68 GPa and a Poisson's ratio of approximately 0.17 [16].…”

Application of induced mechanical stresses in formation of spherical surfaces of interference mirror substrates

“…Деталь приклеивается на планшайбу напротив отверстия для подачи в образовавшуюся полость жидкости от гидравлической системы (3). Нагнетаемое давление P выгибает полученную мембрану, формируя выпуклую сферическую поверхность (4).…”

“…Но данным подходом не ограничиваются современные возможности формообразования оптических деталей [1,2]. Существенными дополнениями являются показавшие эффективность прецизионные технологии магнитореологической полировки [3][4][5], ионного травления [5][6][7] и методы формообразования посредством осаждения неравнотолщинных покрытий [8][9][10]. В основном эти технологии используют после механической полировки на этапе финишной корректировки оптических деталей, решения задач по созданию асферических или иных поверхностей со сложным профилем.…”

Early study on the application of Nexcera ultra low thermal expansion ceramic to space telescopes

“…NEXCERA MATERIAL PROPERTIES Ultra low thermal expansion ceramic NEXCERA is a cordierite (2MgO-2Al 2 O 3 -5SiO 2 ) based ceramic and has advanced material properties to meet severe requirements of space applications. Its key properties are a high specific stiffness (140 GPa / 2.55 g/cm 3 ) [2] and high long term stability (0.01 ppm / 13 months) [1] combined with an extremely low CTE (< 0.03 ppm/K) at room temperature [2]. Its high stability against thermal disturbance and secular change allow it to be applied to optical components in earth orbiting satellites.…”

“…The excellent polishing characteristics and new development of material composition suitable for mirror applications were also reported in a recent paper. This material was polished to a precise mirror surface using Magnetorheological Finishing (MRF) technology and provided the best surface roughness of less than 1nm RMS [2]. For these reasons, NEXCERA has been used not only as structural components such as calibration tools and primary standards but also as optical reflecting mirrors in the precision metrology field requiring high accuracy and stability.…”