Gratings for integrated optics by electron lithography.

The electron lithographic fabrication of high quality diffraction gratings with periods in the 0.25-microm < a(o) < 1.5-microm range is reported. The negative electron resist employed is a copolymer of glycidyl methacrylate and ethyl acrylate with a sensitivity about 15 times better than that of poly(methyl methacrylate), a positive resist. A new scan generator with linearity accurate to 1 part in 10(4) and locked onto the 60-Hz power supplies is described. Gratings with up to 3000 lines were fabricated with long range order deltaa(o)/a(o) </= 5 </= 10(-4). The use of the negative resist gratings as couplers for thin-slab dielectric waveguides is demonstrated. It was found that efficiencies up to 20% could be obtained in the range 0.5 < lambda(o)/a(o) < 1.1.