Fabrication of high numerical aperture zone plates using deep ultraviolet lithography

Linear zone plates with a minimum linewidth of 0.69 μm are fabricated by electron-beam writing and deep UV lithographic techniques. The focusing characteristics are examined for laser beams at 0.633 and 0.86 μm in wavelength. A focal length of 200 m, minimum spot size of 1.0 μm, and a numerical aperture of 0.42 are obtained at λ = 0.633 μm. Possible applications of the present technology to the fabrication of miniaturized focusing elements for opto-electronics are discussed.