Direct-Write Optical Lithography for High-Energy Diffractive Optics

Synchrotron and free-electron-laser facilities require diffraction gratings, with precisely defined specifications, for spectrometers and monochrometers on their X-ray and vacuum- ultraviolet (VUV) beamlines. With only 3 commercial suppliers worldwide, diffraction-grating availability is often constrained by long delivery times and high cost. Moreover, the techniques currently used by commercial suppliers to fabricate beamline gratings, i.e., holographic lithography or the inscribing of individual grating lines, are often unable to meet the demanding specifications, especially for absolute line-placement accuracy of variable line-space and curved-line gratings. In Phase I, company will make modifications to its zone-plate-array-lithography platform that will enable it to provide fast turn-around on variable line-space gratings on substrates thicker than 25mm, longer than 150 mm and with absolute line-placement accuracy of less than 20 nm. In Phase II, absolute line-placement accuracy of less than 10 nm will be demonstrated on substrates thicker than 25mm and longer than 250 mm. Also in Phase II, grating spatial periods in excess of 2400 lines per mm will be demonstrated as well as blazed grating in single-crystal silicon. In addition to capturing a substantial fraction of the world-wide commercial market for X-ray and vacuum-ultraviolet gratings, achieving sub-10nm absolute pattern-placement accuracy over large areas will open new markets. In particular, a market will be opened for high-accuracy computer-generated holograms on thick substrates, needed to provide reference wavefronts for interferometric null testing during the manufacture of aspheric, cylindrical and other free-form optical surfaces.