Axial shift mapping: a self-referencing test for measuring the axial figure of near-cylindrical surfaces.

Lateral shearing self-referencing interferometry methods shift the surface under test between measurements to separate its topography from that of the reference surface. However, rigid body errors occur during shifting, creating an ambiguity in the quadratic term of the extracted surfaces. We present axial shift mapping, a lateral shearing self-referencing interferometry method for cylinders, in which the quadratic ambiguity is resolved by measuring the rigid body errors using known artifact mirrors residing in the interferometer's field of view.

Ultrafast laser stress figuring for accurate deformation of thin mirrors.

Fabricating freeform mirrors relies on accurate optical figuring processes capable of arbitrarily modifying low-spatial frequency height without creating higher-spatial frequency errors. We present a scalable process to accurately figure thin mirrors using stress generated by a focused ultrafast laser. We applied ultrafast laser stress figuring (ULSF) to four thin fused silica mirrors to correct them to 10-20 nm RMS over 28 Zernike terms, in 2-3 iterations, without significantly affecting higher-frequency errors.

Optical design of diffraction-limited x-ray telescopes.

Astronomical imaging with micro-arcsecond (µas) angular resolution could enable breakthrough scientific discoveries. Previously proposed µas x-ray imager designs have been interferometers with limited effective collecting area. Here we describe x-ray telescopes achieving diffraction-limited performance over a wide energy band with large effective area, employing a nested-shell architecture with grazing-incidence mirrors, while matching the optical path lengths between all shells.

Compensating film stress in thin silicon substrates using ion implantation.

Future space telescopes, especially X-ray telescopes, will require thin mirrors to achieve high optical throughput. Thin mirrors are more difficult to fabricate than thick mirrors, but recent advances have made accurate fabrication of thin mirrors possible. However, mirrors must have a reflective coating, which typically has non-repeatable and non-uniform intrinsic stress that deforms a thin mirror.

Thermal oxide patterning method for compensating coating stress in silicon substrates.

We introduce a novel method for correcting distortion in thin silicon substrates caused by coating stress. Thin substrates, such as lightweight mirrors for x-ray or optical imaging, and semiconductor wafers or flat panel substrates, are easily distorted by stress in thin film coatings. We report a new method for correcting stress-induced distortion in flat silicon substrates which utilizes a micro-patterned silicon oxide layer on the back side of the substrate.

Correcting flat mirrors with surface stress: analytical stress fields.

Thin mirrors, important for next-generation space telescopes, are difficult to accurately fabricate. One approach is to fabricate a mirror using traditional methods, then to bend the mirror using surface stress to correct residual height errors. We present two surface stress fields that correct any height error field in thin flat plates.