JENA, Germany -- The development of a step-by-step fabrication process for diffractive optical elements was announced in the final report of a European research alliance concerned with discoveries and applications in the field.The partnership, known as the Flat Optical Element Technologies and Applications (FOTA) project, presented its summary in September at the Friedrich Schiller University Jena. The EUREKA project, a consortium of European companies, universities and governments working toward the advancement of science and industry, supported the effort. FOTA's goal is to show the feasibility of the fabrication of wavelength-scale diffractive optical elements and gratings.According to the report, FOTA developed a process for fabricating high-spatial-frequency diffractive optical elements. These steps include electron beam writing, photolithographic grating transfer to about 0.3 µm, proportional etching in hard materials and replication in plastic materials down to approximately 0.3 µm. Project Manager Olivier Parriaux at the university said that currently no single facility can perform all of the fabrication steps and that such a capability could substantially extend the diffractive optical elements market to other fields.In addition, the project facilitated the development of a generic line of diffractive interferometric rotation and translation encoder sensors capable of 1-nm resolution and 50-nm accuracy. Baumer Electric and the Société Genevoise des Instruments de Physique, Switzerland, produced the encoders, which use short-pitch gratings to provide more than 100,000 impulses per turn without interpolation. The technique could lead to smaller, more cost-effective sensors with 10 to 100 times greater resolution, said Parriaux. The encoders are expected to hit the market next year. Theory to applicationThe report concluded with recommendations to consolidate the set of fabrication and characterization methods, as well as to further investigate the applications that could benefit from the new technologies. Parriaux said that the manufacturers and users of simple sensors and microsystems, evanescent wave biochemical sensors, and solid-state and semiconductor lasers could also benefit from the group's achievements.Although FOTA has officially finished its work, computer interconnect efforts headed by Thomson CSF will continue through 1997.