This paper describes the manufacturing steps necessary to manufacture hemispherical concave aspheric mirrors for high- NA systems. The process chain is considered from generation to final figuring and includes metrology testing during the various manufacturing steps. Corning Incorporated has developed this process by taking advantage of recent advances in commercially available Satisloh and QED Technologies equipment. Results are presented on a 100 mm concave radius nearly hemispherical (NA = 0.94) fused silica sphere with a better than 5 nm RMS figure. Part interferometric metrology was obtained on a QED stitching interferometer. Final figure was made possible by the implementation of a high-NA rotational MRF mode recently developed by QED Technologies which is used at Corning Incorporated for production. We also present results from a 75 mm concave radius (NA = 0.88) Corning ULE sphere that was produced using sub-aperture tools from generation to final figuring. This part demonstrates the production chain from blank to finished optics for high-NA concave asphere.
Increased laser durability is realized by F-SiO2 protected coatings on CaF2 with subsurface-damage-free surface finishing. Surface reflection loss is reduced by fluoride-based antireflection coatings. The F-SiO2 protective coating approach can be extended to the fluoride-based AR coatings on subsurface-damage-free CaF2 optics. In this contribution, a laser-induced damage test was performed on an F-SiO2 protected fluoride-based AR coating on a subsurface-damage-free (SSD-free) CaF2 window with an ArF laser. Similar laser damage resistance was realized on the protected AR coated optics with more than 9% transmission gain when compared to that of the F-SiO2 coated.
A method for measuring symmetric aberrations in large departure aspheric surfaces to nearly single digit nanometer precision is demonstrated. Interferometry can accurately measure plano, spherical and small departure aspheric surfaces. However, null correction is normally required for accurate interferometric measurement of large departure aspheres. When using conventional null lenses, asymmetric aberrations are easily measured by simply rotating the surface under test to a finite number of positions and comparing them to one another. The rotationally symmetric errors are more difficult to know with certainty due to possible systematic rotationally symmetric errors with the null lens itself. The proposed system can measure aspheres on planar to f/6.0 spherical surfaces with a maximum sag of 1 mm and from 800 mm to 25 mm spherical surfaces down to f/0.55. A non-contact interferometric probe is used to measure the surface profile with the optic mounted on either a linear or rotary air bearing, depending on the base radius of curvature of the optic. Measurement results are shown for several aspheres and compared with interferometer measurements.
A polarizing beamsplitter used for the OMEGA Upgrade, was produced using the hafnia/silica combination. These coatings have stringent optical requirements, are placed in the stages of the laser with the highest fluence at 1054 nm, and are required to have a low net stress to produce low wavefront distortion. Hafnia/silica coatings are also more stable than other film combinations such as tantala/silica. Hafnia/silica films were investigated for other applications. A triple wavelength antireflection coating was developed for calorimeter absorption glass. The metal-converted hafnia is also used on selected transport mirrors used at 351 nm and angles of incidence up to 45 degrees. Damage test results for 1054 nm, 1 ns, and 351 nm, 0.7 ns will be presented.