Effects of fabrication errors on the performance of cylindrical diffractive lenses: rigorous boundary-element method and scalar approximation

The effects of fabrication errors on the performance of collimating finite-thickness cylindrical diffractive lenses with eight discrete levels are investigated with a rigorous boundary-element method and a scalar approach. The photolithographic fabrication errors considered are mask alignment errors, exposure errors (that result in linewidth errors), and etch-depth errors. A cylindrical Gaussian beam of TE or TM polarization is incident upon the resulting lenses. Lenses of F/4, F/2, and F/1.4 are examined. The diffraction efficiencies of the lenses with fabrication errors are generally lower than the error-free lenses with the most severe performance degradation occurring for mask misalignment and exposure errors.