Binary and multilevel diffractive lenses with submicrometer feature sizes

Binary and multilevel diffractive lenses with submicrometer feature sizes are realized on silicon and galliumphosphide wafers using CAD methods, direct write e-beam lithography, reactive ion etching, antireflection coating, and wafer dicing. Measurements prove aberration-free imaging and maximum diftraction efficiencies of 70% for lenses with high numerical aperture (NA) of 0.5. Comparisons to other miniature and micro-optical elements are carried out with respect to laser-to-single-mode-fiber coupling and show the competitive performance of the diffractive lenses. Arrays for 18-channel parallel receiver modules are fabricated in on-axis and off-axis versions. Optical crosstalk is estimated.