Abstract

We have fabricated a free-standing transmission Fresnel zone plate for the focusing of long-thermal-wavelength neutral atoms. The zone plate was fabricated from a 0.7μm thick boron-doped silicon membrane. The pattern was formed by means of electron-beam lithography, and the final grating was generated by reactive ion etching. The zone plate is composed of 100 zones, the diameter of the outermost zone is approximately 80 μm. The zone plate is designed to focus incident atoms having a thermal wavelength of 17 Å into a 2000 Å spot at a focal length of about 1 cm. A maximum of 8% of the incident flux will be transmitted and focused into the primary spot with this design. The use of diffraction optics for the focusing of an atomic beam is novel in that it does not rely on any electromagnetic forces for achieving focusing. As a result, this approach can be used to focus any particle with a long thermal de Broglie wavelength.

© 1990 Optical Society of America