100-picometer interferometry for EUVL

Abstract

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High-Contrast Imaging using Adaptive Optics for Extrasolar Planet Detection

“…In PSDI mode, the testbed becomes an extremely accurate optical metrology system [51]. The PSDI was developed at Lawrence Livermore National Laboratory for metrology of complex aspheric optics.…”

“…The phase shifting diffraction interferometer (PSDI) was developed at Lawrence Livermore National Laboratory for metrology of aspheric optics for use at ultra-violet wavelengths [51]. In its original configuration the PSDI has an absolute wavefront accuracy of 100 pm.…”

“…This challenging application required metrology with 100 pm accuracy [51]. The PSDI is a proven optical metrology technology that can provide the absolute wavefront accuracy needed for high-contrast imaging.…”

“…It is implemented using fast fourier transforms in two steps: from the CCD to the focal plane, and from the focal plane to the pupil plane [52]. In early tests, the paraxial approximation was used, but it was not accurate enough [51].…”

“…We have already demonstrated an ability to operate at contrast levels of 10 −7 to 10 −8 [26]. The extremely accurate optical metrology of the phase shifting diffraction interferometer (PSDI) [51] allows absolute measurements of the MEMS DM. Using the PSDI as the wavefront sensor, we have flattened to < 1 nm rms over controllable spatial frequencies.…”