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Pulse compression grating fabrication by diffractive proximity photolithography

: Stürzebecher, Lorenz; Fuchs, Frank; Harzendorf, Torsten; Zeitner, Uwe Detlef


Optics Letters 39 (2014), No.4, pp.1042-1045
ISSN: 0146-9592
Journal Article
Fraunhofer IOF ()

We report about a newly devised throughput-scalable fabrication method for high-quality periodic submicron structures. The process is demonstrated for optical transmission gratings in fused silica with a period of 800 nm (1250 lines/mm) to be used in laser pulse compression. The technology is based on an innovative advancement of i-line proximity photolithography performed in a mask aligner. The aerial image is encoded in a rigorously optimized electron-beam-written three-level phase mask which is illuminated by an adapted multipole configuration of incidence angles. In comparison to conventional proximity lithography, the process enables a significantly higher resolution while maintaining a good depth of focus—in contrast to lithography based on direct Talbot-imaging. Details about the grating fabrication process and characterization of fabricated pulse compression grating wafers are presented. The gratings show a diffraction efficiency of 97% at a wavelength of 1030 nm and a wavefront error comparable to gratings fabricated by electron-beam lithography.