The fabrication of high resolution diffractive elements by electron beam microlithography

Lithographic techniques and the authors´ electron beam lithography facility have been described. Resolution limits through electron scattering in the resist (proximity effect) are mentioned and calibration devices for the experimental study of the main parameters influencing the resolution of electron beam lithography have been given. To determine the energy distribution in the resist film a novel calibration device was presented and results for different film thicknesses shown. A high reflectivity surface-relief grating was plotted onto a single-mode optical fibre with a grating period of 0.8 μm. It was designed to act as an external cavity line-narrowed frequency selective output for a semiconductor laser diode. The side mode reduction ratio of the output spectrum is approximately 30 dB. A second example is a 1 to 256 fan-out hologram which was plotted as a binary relief structure. The efficiency of this element was within 10% of the theoretically predicted efficiency