Laser beam lithographed micro-Fresnel lenses.

Laser beam lithography for micro-Fresnel lenses (MFLs) with blazed grooves is proposed and demonstrated including the system configuration and characteristics of the resulting lenses. The resolution is even better than that of electron-beam lithography in forming 1-microm deep relief gratings in resist. A laser beam lithographed MFL with a diameter as large as 9.6 mm is described as well as a compact MFL (N.A. 0.21) butt coupled to an optical waveguide. In these two distinct MFLs, nearly diffraction-limited spot sizes have been obtained with diffraction efficiencies of 50% or more. A specific MFL array used for an integrated optic laser Doppler velocimeter is also presented.